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drop unused: toplevel, assign-only

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- assign statement does not count towards variable usage by default
- only works with assignments on the same scope level as declaration
- can be disabled with `unused` set to "keep_assign"
- `toplevel` to drop unused top-level variables and/or functions
- `top_retain` to whitelist top-level exceptions

closes #1450
This commit is contained in:
alexlamsl
2017-02-18 19:03:53 +08:00
parent d11dca3cf9
commit 148047fbbf
4 changed files with 565 additions and 10 deletions
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72
lib/compress.js
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@@ -60,6 +60,8 @@ function Compressor(options, false_by_default) {
booleans : !false_by_default,
loops : !false_by_default,
unused : !false_by_default,
toplevel : !!options["top_retain"],
top_retain : null,
hoist_funs : !false_by_default,
keep_fargs : true,
keep_fnames : false,
@@ -80,6 +82,21 @@ function Compressor(options, false_by_default) {
global_defs : {},
passes : 1,
}, true);
var top_retain = this.options["top_retain"];
if (top_retain instanceof RegExp) {
this.top_retain = function(def) {
return top_retain.test(def.name);
};
} else if (typeof top_retain === "function") {
this.top_retain = top_retain;
} else if (top_retain) {
if (typeof top_retain === "string") {
top_retain = top_retain.split(/,/);
}
this.top_retain = function(def) {
return top_retain.indexOf(def.name) >= 0;
};
}
var sequences = this.options["sequences"];
this.sequences_limit = sequences == 1 ? 200 : sequences | 0;
this.warnings_produced = {};
@@ -1409,13 +1426,27 @@ merge(Compressor.prototype, {
AST_Scope.DEFMETHOD("drop_unused", function(compressor){
var self = this;
if (compressor.has_directive("use asm")) return self;
var toplevel = compressor.option("toplevel");
if (compressor.option("unused")
&& !(self instanceof AST_Toplevel)
&& (!(self instanceof AST_Toplevel) || toplevel)
&& !self.uses_eval
&& !self.uses_with
) {
&& !self.uses_with) {
var assign_as_unused = !/keep_assign/.test(compressor.option("unused"));
var drop_funcs = /funcs/.test(toplevel);
var drop_vars = /vars/.test(toplevel);
if (!(self instanceof AST_Toplevel) || toplevel == true) {
drop_funcs = drop_vars = true;
}
var in_use = [];
var in_use_ids = {}; // avoid expensive linear scans of in_use
if (self instanceof AST_Toplevel && compressor.top_retain) {
self.variables.each(function(def) {
if (compressor.top_retain(def) && !(def.id in in_use_ids)) {
in_use_ids[def.id] = true;
in_use.push(def);
}
});
}
var initializations = new Dictionary();
// pass 1: find out which symbols are directly used in
// this scope (not in nested scopes).
@@ -1423,11 +1454,25 @@ merge(Compressor.prototype, {
var tw = new TreeWalker(function(node, descend){
if (node !== self) {
if (node instanceof AST_Defun) {
if (!drop_funcs && scope === self) {
var node_def = node.name.definition();
if (!(node_def.id in in_use_ids)) {
in_use_ids[node_def.id] = true;
in_use.push(node_def);
}
}
initializations.add(node.name.name, node);
return true; // don't go in nested scopes
}
if (node instanceof AST_Definitions && scope === self) {
node.definitions.forEach(function(def){
if (!drop_vars) {
var node_def = def.name.definition();
if (!(node_def.id in in_use_ids)) {
in_use_ids[node_def.id] = true;
in_use.push(node_def);
}
}
if (def.value) {
initializations.add(def.name.name, def.value);
if (def.value.has_side_effects(compressor)) {
@@ -1437,6 +1482,14 @@ merge(Compressor.prototype, {
});
return true;
}
if (assign_as_unused
&& node instanceof AST_Assign
&& node.operator == "="
&& node.left instanceof AST_SymbolRef
&& scope === self) {
node.right.walk(tw);
return true;
}
if (node instanceof AST_SymbolRef) {
var node_def = node.definition();
if (!(node_def.id in in_use_ids)) {
@@ -1496,7 +1549,7 @@ merge(Compressor.prototype, {
}
}
}
if (node instanceof AST_Defun && node !== self) {
if (drop_funcs && node instanceof AST_Defun && node !== self) {
if (!(node.name.definition().id in in_use_ids)) {
compressor.warn("Dropping unused function {name} [{file}:{line},{col}]", {
name : node.name.name,
@@ -1508,7 +1561,7 @@ merge(Compressor.prototype, {
}
return node;
}
if (node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
if (drop_vars && node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
var def = node.definitions.filter(function(def){
if (def.name.definition().id in in_use_ids) return true;
var w = {
@@ -1571,6 +1624,15 @@ merge(Compressor.prototype, {
}
return node;
}
if (drop_vars && assign_as_unused
&& node instanceof AST_Assign
&& node.operator == "="
&& node.left instanceof AST_SymbolRef) {
var def = node.left.definition();
if (!(def.id in in_use_ids) && self.variables.get(def.name) === def) {
return node.right;
}
}
if (node instanceof AST_For) {
descend(node, this);