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preserve non-constant value assignments with modifications (#2997)

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fixes #2995
This commit is contained in:
Alex Lam S.L
2018-03-13 17:35:34 +08:00
committed by GitHub
parent b9f72a4a81
commit 5429234138
2 changed files with 54 additions and 2 deletions
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27
lib/compress.js
View File

@@ -3114,6 +3114,8 @@ merge(Compressor.prototype, {
var in_use = [];
var in_use_ids = Object.create(null); // avoid expensive linear scans of in_use
var fixed_ids = Object.create(null);
var value_read = Object.create(null);
var value_modified = Object.create(null);
if (self instanceof AST_Toplevel && compressor.top_retain) {
self.variables.each(function(def) {
if (compressor.top_retain(def) && !(def.id in in_use_ids)) {
@@ -3381,6 +3383,17 @@ merge(Compressor.prototype, {
);
self.transform(tt);
function verify_safe_usage(def, read, modified) {
if (def.id in in_use_ids) return;
if (read && modified) {
in_use_ids[def.id] = true;
in_use.push(def);
} else {
value_read[def.id] = read;
value_modified[def.id] = modified;
}
}
function scan_ref_scoped(node, descend) {
var node_def, props = [], sym = assign_as_unused(node, props);
if (sym instanceof AST_SymbolRef
@@ -3390,8 +3403,18 @@ merge(Compressor.prototype, {
});
if (node instanceof AST_Assign) {
node.right.walk(tw);
if (node.left === sym && !node_def.chained && sym.fixed_value() === node.right) {
fixed_ids[node_def.id] = node;
if (node.left === sym) {
if (!node_def.chained && sym.fixed_value() === node.right) {
fixed_ids[node_def.id] = node;
}
if (!node.write_only) {
verify_safe_usage(node_def, true, value_modified[node_def.id]);
}
} else {
var fixed = sym.fixed_value();
if (!fixed || !fixed.is_constant()) {
verify_safe_usage(node_def, value_read[node_def.id], true);
}
}
}
return true;

29
test/compress/drop-unused.js
View File

@@ -1785,3 +1785,32 @@ issue_805_2: {
"bar",
]
}
issue_2995: {
options = {
pure_getters: "strict",
reduce_vars: true,
unused: true,
}
input: {
function f(a) {
var b;
a.b = b = function() {};
b.c = "PASS";
}
var o = {};
f(o);
console.log(o.b.c);
}
expect: {
function f(a) {
var b;
a.b = b = function() {};
b.c = "PASS";
}
var o = {};
f(o);
console.log(o.b.c);
}
expect_stdout: "PASS"
}