542 lines
22 KiB
JavaScript
542 lines
22 KiB
JavaScript
var U = require("./node");
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var List = U.List;
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var sandbox = require("./sandbox");
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// Reduce a ufuzz-style `console.log` based test case by iteratively replacing
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// AST nodes with various permutations. Each AST_Statement in the tree is also
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// speculatively dropped to determine whether it is needed. If the altered
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// tree and the last known good tree produce the same non-nil error-free output
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// after being run, then the permutation survives to the next generation and
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// is the basis for subsequent iterations. The test case is reduced as a
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// consequence of complex expressions being replaced with simpler ones.
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// This function assumes that the testcase will not result in a parse or
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// runtime Error. Note that a reduced test case will have different runtime
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// output - it is not functionally equivalent to the original. The only criteria
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// is that once the generated reduced test case is run without minification, it
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// will produce different output from the code minified with `minify_options`.
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// Returns a `minify` result object with an additonal boolean property `reduced`.
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module.exports = function reduce_test(testcase, minify_options, reduce_options) {
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minify_options = minify_options || { compress: {}, mangle: false };
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reduce_options = reduce_options || {};
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var max_iterations = reduce_options.max_iterations || 1000;
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var max_timeout = reduce_options.max_timeout || 15000;
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var verbose = reduce_options.verbose;
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var minify_options_json = JSON.stringify(minify_options, null, 2);
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var timeout = 1000; // start with a low timeout
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var result_cache = Object.create(null);
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var differs;
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if (testcase instanceof U.AST_Node) testcase = testcase.print_to_string();
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// the initial timeout to assess the viability of the test case must be large
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if (differs = producesDifferentResultWhenMinified(result_cache, testcase, minify_options, max_timeout)) {
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if (differs.error) return differs;
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// Replace expressions with constants that will be parsed into
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// AST_Nodes as required. Each AST_Node has its own permutation count,
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// so these replacements can't be shared.
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// Although simpler replacements are generally faster and better,
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// feel free to experiment with a different replacement set.
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var REPLACEMENTS = [
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// "null", "''", "false", "'foo'", "undefined", "9",
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"1", "0",
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];
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// There's a relationship between each node's _permute counter and
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// REPLACEMENTS.length which is why fractional _permutes were needed.
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// One could scale all _permute operations by a factor of `steps`
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// to only deal with integer operations, but this works well enough.
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var steps = 4; // must be a power of 2
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var step = 1 / steps; // 0.25 is exactly representable in floating point
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var tt = new U.TreeTransformer(function(node, descend, in_list) {
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if (CHANGED) return;
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// quick ignores
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if (node instanceof U.AST_Accessor) return;
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if (node instanceof U.AST_Directive) return;
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if (node instanceof U.AST_Label) return;
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if (node instanceof U.AST_LabelRef) return;
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if (!in_list && node instanceof U.AST_SymbolDeclaration) return;
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if (node instanceof U.AST_Toplevel) return;
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var parent = tt.parent();
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// ensure that the _permute prop is a number.
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// can not use `node.start._permute |= 0;` as it will erase fractional part.
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if (typeof node.start._permute === "undefined") node.start._permute = 0;
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// if node reached permutation limit - skip over it.
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// no structural AST changes before this point.
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if (node.start._permute >= REPLACEMENTS.length) return;
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if (parent instanceof U.AST_Assign
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&& parent.left === node
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|| parent instanceof U.AST_Unary
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&& parent.expression === node
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&& ["++", "--", "delete"].indexOf(parent.operator) >= 0) {
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// ignore lvalues
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return;
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}
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if ((parent instanceof U.AST_For || parent instanceof U.AST_ForIn)
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&& parent.init === node && node instanceof U.AST_Var) {
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// preserve for (var ...)
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return node;
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}
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// node specific permutations with no parent logic
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if (node instanceof U.AST_Array) {
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var expr = node.elements[0];
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if (expr && !(expr instanceof U.AST_Hole)) {
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node.start._permute++;
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CHANGED = true;
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return expr;
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}
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}
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else if (node instanceof U.AST_Binary) {
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CHANGED = true;
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return [
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node.left,
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node.right,
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][ ((node.start._permute += step) * steps | 0) % 2 ];
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}
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else if (node instanceof U.AST_Catch || node instanceof U.AST_Finally) {
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// drop catch or finally block
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node.start._permute++;
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CHANGED = true;
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return null;
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}
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else if (node instanceof U.AST_Conditional) {
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CHANGED = true;
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return [
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node.condition,
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node.consequent,
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node.alternative,
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][ ((node.start._permute += step) * steps | 0) % 3 ];
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}
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else if (node instanceof U.AST_BlockStatement) {
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if (in_list) {
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node.start._permute++;
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CHANGED = true;
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return List.splice(node.body);
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}
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}
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else if (node instanceof U.AST_Call) {
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var expr = [
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node.expression,
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node.args[0],
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null, // intentional
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][ ((node.start._permute += step) * steps | 0) % 3 ];
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if (expr) {
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CHANGED = true;
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return expr;
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}
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if (node.expression instanceof U.AST_Function) {
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// hoist and return expressions from the IIFE function expression
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var body = node.expression.body;
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node.expression.body = [];
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var seq = [];
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body.forEach(function(node) {
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var expr = expr instanceof U.AST_Exit ? node.value : node.body;
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if (expr instanceof U.AST_Node && !is_statement(expr)) {
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// collect expressions from each statements' body
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seq.push(expr);
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}
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});
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CHANGED = true;
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return to_sequence(seq);
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}
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}
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else if (node instanceof U.AST_Defun) {
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switch (((node.start._permute += step) * steps | 0) % 2) {
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case 0:
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CHANGED = true;
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return List.skip;
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case 1:
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if (!has_exit(node)) {
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// hoist function declaration body
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var body = node.body;
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node.body = [];
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body.push(node); // retain function with empty body to be dropped later
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CHANGED = true;
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return List.splice(body);
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}
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}
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}
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else if (node instanceof U.AST_DWLoop) {
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var expr = [
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node.condition,
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node.body,
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null, // intentional
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][ (node.start._permute * steps | 0) % 3 ];
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node.start._permute += step;
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if (!expr) {
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if (node.body[0] instanceof U.AST_Break) {
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if (node instanceof U.AST_Do) {
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CHANGED = true;
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return List.skip;
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}
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expr = node.condition; // AST_While - fall through
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}
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}
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if (expr && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
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CHANGED = true;
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return to_statement(expr);
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}
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}
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else if (node instanceof U.AST_PropAccess) {
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var expr = [
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node.expression,
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node.property instanceof U.AST_Node && node.property,
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][ node.start._permute++ % 2 ];
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if (expr) {
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CHANGED = true;
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return expr;
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}
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}
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else if (node instanceof U.AST_For) {
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var expr = [
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node.init,
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node.condition,
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node.step,
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node.body,
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][ (node.start._permute * steps | 0) % 4 ];
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node.start._permute += step;
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if (expr && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
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CHANGED = true;
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return to_statement(expr);
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}
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}
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else if (node instanceof U.AST_ForIn) {
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var expr = [
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node.init,
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node.object,
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node.body,
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][ (node.start._permute * steps | 0) % 3 ];
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node.start._permute += step;
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if (expr && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
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CHANGED = true;
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return to_statement(expr);
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}
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}
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else if (node instanceof U.AST_If) {
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var expr = [
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node.condition,
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node.body,
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node.alternative,
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][ (node.start._permute * steps | 0) % 3 ];
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node.start._permute += step;
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if (expr) {
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// replace if statement with its condition, then block or else block
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CHANGED = true;
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return to_statement(expr);
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}
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}
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else if (node instanceof U.AST_Object) {
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// first property's value
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var expr = node.properties[0] instanceof U.AST_ObjectKeyVal && node.properties[0].value;
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if (expr) {
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node.start._permute++;
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CHANGED = true;
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return expr;
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}
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}
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else if (node instanceof U.AST_SimpleStatement) {
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if (node.body instanceof U.AST_Call && node.body.expression instanceof U.AST_Function) {
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// hoist simple statement IIFE function expression body
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node.start._permute++;
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if (!has_exit(node.body.expression)) {
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var body = node.body.expression.body;
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node.body.expression.body = [];
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CHANGED = true;
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return List.splice(body);
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}
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}
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}
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else if (node instanceof U.AST_Switch) {
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var expr = [
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node.expression, // switch expression
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node.body[0] && node.body[0].expression, // first case expression or undefined
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node.body[0] && node.body[0], // first case body or undefined
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][ (node.start._permute * steps | 0) % 4 ];
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node.start._permute += step;
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if (expr && (!(expr instanceof U.AST_Statement) || !has_loopcontrol(expr, node, parent))) {
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CHANGED = true;
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return expr instanceof U.AST_SwitchBranch ? new U.AST_BlockStatement({
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body: expr.body.slice(),
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start: {},
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}) : to_statement(expr);
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}
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}
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else if (node instanceof U.AST_Try) {
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var body = [
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node.body,
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node.bcatch && node.bcatch.body,
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node.bfinally && node.bfinally.body,
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null, // intentional
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][ (node.start._permute * steps | 0) % 4 ];
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node.start._permute += step;
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if (body) {
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// replace try statement with try block, catch block, or finally block
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CHANGED = true;
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return new U.AST_BlockStatement({
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body: body,
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start: {},
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});
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} else {
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// replace try with a break or return if first in try statement
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if (node.body[0] instanceof U.AST_Break
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|| node.body[0] instanceof U.AST_Return) {
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CHANGED = true;
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return node.body[0];
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}
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}
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}
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else if (node instanceof U.AST_Unary) {
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node.start._permute++;
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CHANGED = true;
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return node.expression;
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}
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else if (node instanceof U.AST_Var) {
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if (node.definitions.length == 1 && node.definitions[0].value) {
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// first declaration value
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node.start._permute++;
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CHANGED = true;
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return to_statement(node.definitions[0].value);
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}
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}
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else if (node instanceof U.AST_LabeledStatement) {
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if (node.body instanceof U.AST_Statement
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&& !has_loopcontrol(node.body, node.body, node)) {
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// replace labelled statement with its non-labelled body
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node.start._permute = REPLACEMENTS.length;
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CHANGED = true;
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return node.body;
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}
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}
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if (in_list) {
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// special case to drop object properties and switch branches
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if (parent instanceof U.AST_Object
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|| parent instanceof U.AST_Switch && parent.expression != node) {
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node.start._permute++;
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CHANGED = true;
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return List.skip;
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}
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// replace or skip statement
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if (node instanceof U.AST_Statement) {
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node.start._permute++;
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CHANGED = true;
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return List.skip;
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}
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// remove this node unless its the sole element of a (transient) sequence
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if (!(parent instanceof U.AST_Sequence) || parent.expressions.length > 1) {
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node.start._permute++;
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CHANGED = true;
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return List.skip;
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}
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}
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// replace this node
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var newNode = U.parse(REPLACEMENTS[node.start._permute % REPLACEMENTS.length | 0], {
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expression: true,
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});
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if (is_statement(node)) {
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newNode = new U.AST_SimpleStatement({
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body: newNode,
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start: {},
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});
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}
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newNode.start._permute = ++node.start._permute;
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CHANGED = true;
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return newNode;
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}, function(node, in_list) {
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if (node instanceof U.AST_Sequence) {
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// expand single-element sequence
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if (node.expressions.length == 1) return node.expressions[0];
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}
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else if (node instanceof U.AST_Try) {
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// expand orphaned try block
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if (!node.bcatch && !node.bfinally) return new U.AST_BlockStatement({
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body: node.body,
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start: {},
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});
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}
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else if (node instanceof U.AST_Var) {
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// remove empty var statement
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if (node.definitions.length == 0) return in_list ? List.skip : new U.AST_EmptyStatement({
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start: {},
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});
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}
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});
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for (var pass = 1; pass <= 3; ++pass) {
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var testcase_ast = U.parse(testcase);
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testcase_ast.walk(new U.TreeWalker(function(node) {
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// unshare start props to retain visit data between iterations
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node.start = JSON.parse(JSON.stringify(node.start));
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node.start._permute = 0;
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}));
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for (var c = 0; c < max_iterations; ++c) {
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if (verbose) {
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if (pass == 1 && c % 25 == 0) {
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console.error("// reduce test pass "
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+ pass + ", iteration " + c + ": " + testcase.length + " bytes");
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}
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}
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var CHANGED = false;
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var code_ast = testcase_ast.clone(true).transform(tt);
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if (!CHANGED) break;
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try {
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var code = code_ast.print_to_string();
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} catch (ex) {
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// AST is not well formed.
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// no harm done - just log the error, ignore latest change and continue iterating.
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console.error("*** Error generating code from AST.");
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console.error(ex);
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console.error("*** Discarding permutation and continuing.");
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continue;
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}
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var diff = producesDifferentResultWhenMinified(result_cache, code, minify_options, timeout);
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if (diff) {
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if (diff.timed_out) {
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// can't trust the validity of `code_ast` and `code` when timed out.
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// no harm done - just ignore latest change and continue iterating.
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if (timeout < max_timeout) {
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timeout += 250;
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result_cache = Object.create(null);
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}
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} else if (diff.error) {
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// something went wrong during minify() - could be malformed AST or genuine bug.
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// no harm done - just log code & error, ignore latest change and continue iterating.
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console.error("*** Error during minification.");
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console.error(code);
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console.error(diff.error);
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console.error("*** Discarding permutation and continuing.");
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} else if (is_error(diff.unminified_result)
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&& is_error(diff.minified_result)
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&& diff.unminified_result.name == diff.minified_result.name) {
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// ignore difference in error messages caused by minification
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} else {
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// latest permutation is valid, so use it as the basis of new changes
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testcase_ast = code_ast;
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testcase = code;
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differs = diff;
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}
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}
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}
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if (c == 0) break;
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if (verbose) {
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console.error("// reduce test pass " + pass + ": " + testcase.length + " bytes");
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}
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}
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testcase += "\n// output: " + to_comment(differs.unminified_result)
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+ "\n// minify: " + to_comment(differs.minified_result)
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+ "\n// options: " + to_comment(minify_options_json);
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} else {
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// same stdout result produced when minified
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testcase = "// Can't reproduce test failure with minify options provided:"
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+ "\n// " + to_comment(minify_options_json);
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}
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return U.minify(testcase.replace(/\u001b\[\d+m/g, ""), {
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compress: false,
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mangle: false,
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output: {
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beautify: true,
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braces: true,
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comments: true,
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}
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});
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};
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function to_comment(value) {
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return ("" + value).replace(/\n/g, "\n// ");
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}
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function has_exit(fn) {
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var found = false;
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var tw = new U.TreeWalker(function(node) {
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if (found) return found;
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if (node instanceof U.AST_Exit) {
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return found = true;
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}
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if (node instanceof U.AST_Scope && node !== fn) {
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return true; // don't descend into nested functions
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}
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});
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fn.walk(tw);
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return found;
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}
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function has_loopcontrol(body, loop, label) {
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var found = false;
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var tw = new U.TreeWalker(function(node) {
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if (found) return true;
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if (node instanceof U.AST_LoopControl && this.loopcontrol_target(node) === loop) {
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return found = true;
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}
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});
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if (label instanceof U.AST_LabeledStatement) tw.push(label);
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tw.push(loop);
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body.walk(tw);
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return found;
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}
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function is_error(result) {
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return typeof result == "object" && typeof result.name == "string" && typeof result.message == "string";
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}
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function is_statement(node) {
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return node instanceof U.AST_Statement && !(node instanceof U.AST_Function);
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}
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function merge_sequence(array, node) {
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if (node instanceof U.AST_Sequence) {
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array.push.apply(array, node.expressions);
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} else {
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array.push(node);
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}
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return array;
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}
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function to_sequence(expressions) {
|
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if (expressions.length == 0) return new U.AST_Number({value: 0, start: {}});
|
|
if (expressions.length == 1) return expressions[0];
|
|
return new U.AST_Sequence({
|
|
expressions: expressions.reduce(merge_sequence, []),
|
|
start: {},
|
|
});
|
|
}
|
|
|
|
function to_statement(node) {
|
|
return is_statement(node) ? node : new U.AST_SimpleStatement({
|
|
body: node,
|
|
start: {},
|
|
});
|
|
}
|
|
|
|
function run_code(result_cache, code, toplevel, timeout) {
|
|
return result_cache[code] || (result_cache[code] = sandbox.run_code(code, toplevel, timeout));
|
|
}
|
|
|
|
function producesDifferentResultWhenMinified(result_cache, code, minify_options, timeout) {
|
|
var minified = U.minify(code, minify_options);
|
|
if (minified.error) return minified;
|
|
|
|
var toplevel = minify_options.toplevel;
|
|
var unminified_result = run_code(result_cache, code, toplevel, timeout);
|
|
if (/timed out/i.test(unminified_result)) return false;
|
|
|
|
var minified_result = run_code(result_cache, minified.code, toplevel, timeout);
|
|
if (/timed out/i.test(minified_result)) return { timed_out: true };
|
|
|
|
return !sandbox.same_stdout(unminified_result, minified_result) ? {
|
|
unminified_result: unminified_result,
|
|
minified_result: minified_result,
|
|
} : false;
|
|
}
|
|
Error.stackTraceLimit = Infinity;
|