By reducing copies of `AST_Node` arrays, we should be able to reduce:
- memory pressure
- potential bugs caused by multiple references in AST
- duplicated executions of `OPT()`
- empty body
- single `AST_Return`
- single `AST_SimpleStatement`
- avoid `/*#__PURE__*/`
Miscellaneous
- enhance single-use function substitution
fixes#281
- all arguments may accept constant values
- return constant value
- free of side effects
- available & identical across locales and runtime environments
- `mangle` non-exported names
- `unused` on `export` of `function`
- `hoist_funs` on `export`
- `export default`
- prohibit definition statements
- parse `AST_Defun` properly
- drop only unused class and function names
fixes#2001fixes#2004
- remove overlap in functionality of singular, consecutive reference of constant value
- remove workarounds for previous bugs in `lib/scope.js`
- distribute recursive `collapse_single_use_vars()` calls to their respective `OPT(AST_Node)`
- enable collapsing of variables within a single `AST_Definitions`
- allow immediate assignment after declaration of variable
- relax modification rule for immutable value
- fix order of visit for TreeWalker
- remove extraneous code
- rename `screw_ie8` to `ie8`
- rename `mangle.except` to `mangle.reserved`
- rename `mangle.properties.ignore_quoted` to `mangle.properties.keep_quoted`
- compact `sourceMap` options
- more stringent verification on input `options`
- toplevel shorthands
- `ie8`
- `keep_fnames`
- `toplevel`
- `warnings`
- support arrays and unquoted string values on CLI
- drop `fromString` from `minify()`
- `minify()` no longer handles any `fs` operations
- unify order of operations for `mangle_properties()` on CLI & API
- `bin/uglifyjs` used to `mangle_properties()` before even `Compressor`
- `minify()` used to `mangle_properties()` after `Compressor` but before `mangle_names()`
- both will now do `Compressor`, `mangle_names()` then `mangle_properties()`
- `options.parse` / `--parse` for parser options beyond `bare_returns`
- add `mangle.properties.builtins` to disable built-in reserved list
- disable with `--mangle-props builtins` on CLI
- `warnings` now off by default
- add `--warn` and `--verbose` on CLI
- drop `--enclose`
- drop `--export-all`
- drop `--reserved-file`
- use `--mangle reserved` instead
- drop `--reserve-domprops`
- enabled by default, disable with `--mangle-props domprops`
- drop `--prefix`
- use `--source-map base` instead
- drop `--lint`
- remove `bin/extract-props.js`
- limit exposure of internal APIs
- update documentations
closes#96closes#102closes#136closes#166closes#243closes#254closes#261closes#311closes#700closes#748closes#912closes#1072closes#1366fixes#101fixes#123fixes#124fixes#263fixes#379fixes#419fixes#423fixes#461fixes#465fixes#576fixes#737fixes#772fixes#958fixes#1036fixes#1142fixes#1175fixes#1220fixes#1223fixes#1280fixes#1359fixes#1368
Improved catch handling in `figure_out_scope()` means special case treatment of IE8 is no longer valid in `reset_opt_flags()`.
Also fixed recursive assignment in variable definition.
`AST_Node.optimize()` is context-aware, so don't cache its results to be used elsewhere.
Also fixed a few cases of AST corruption and beef up safety of `pure_getters`.
- property access to `null` & `undefined` always has side effects
- utilise `reduce_vars` to determine safe property access
- may-be cases treated as side effects unless `unsafe`
Although it would be nice to enforce `AST_Node` cloning during transformation, that ship has sailed a long time ago.
We now get the assigned value when resolving `AST_SymbolRef` instead of `reset_opt_flags()`, which has the added advantage of improved compressor efficiency.
fixes#1787
- fix side effects in switch condition for singular blocks
- fix `undefined` confusion with local variable
- gate `OPT(AST_Switch)` with `switches`
fixes#1758fixes#1759
- `side_effects` will clean up inner statements, so checking for an empty function body should suffice
- drop side effects when dropping `return` from statement
- move these optimisations out from `Compressor` to `OutputStream`
- fixes behaviour inconsistency when running uglified code from global or module levels due to redefinition
When fixing catch-related issue in #1715, it tries to optimise for duplicate definitions but did not take anonymous functions into account.
Remove such optimisation for now and we can cover this as a more general rule later.
`statement_to_expression()` drops `typeof` even if it operates on undeclared variables.
Since we now have `drop_side_effect_free()`, replace and remove this deprecated functionality.
Unlike normal variables and even function definitions, these cannot be reassigned, even though assignment expressions would "leak" the assigned value as normal.
Process variable definitions with or without assigned values against:
- `arguments`
- named function arguments
- multiple definitions within same scope
Essentially demote variable declarations with no value assignments.
Also fixed invalid use of `AST_VarDef` over `arguments` - should use a member of `AST_SymbolDeclaration` instead.
Conditions including strict mode would make `delete` return `true` or `false`, and are too complex to be evaluated by the compressor.
Suppress assignment folding into said operator.
fixes#1685
`AST_Try` is an `AST_Block`, so besides try block we also need to inspect catch and finally blocks for possible side effects.
Also extend this functionality to handle `AST_If` and `AST_LabeledStatement` while we are at it.
fixes#1673
Turns out the only place in `Compressor` which can generate invalid `AST_For.init` is within `drop_unused()`, so focus the fix-up efforts.
supercedes #1652fixes#1656
- #1634 bars variables with cross-scope references in between to collapse
- but if assigned value is side-effect-free, no states can be modified, so it is safe to move
The following is wrong:
`a == (b ? a : c)` => `b`
Because:
- `b` may not be boolean
- `a` might have side effects
- `a == a` is not always `true` (think `NaN`)
- `a == c` is not always `false`
`reduce_vars` enables substitution of variables but did not clone the value's `AST_Node`.
This confuses `collapse_vars` and result in invalid AST and subsequent crash.
fixes#1609
As patched in #1597, `make_node_from_constant()` makes inconsistent and sometimes incorrect calls to `optimize()` and `transform()`.
Fix those issues properly by changing the semantics of `evaluate()` and `make_node_from_constant()`, with the side effect that `evaluate()` no longer eagerly converts constant to `AST_Node`.
Liberal use of `Compressor.transform()` and `AST_Node.optimize()` presents an issue for look-up operations like `TreeWalker.in_boolean_context()` and `TreeWalker.parent()`.
This is an incremental fix such that `AST_Node.optimize()` would now contain the correct stack information when called correctly.
Self-referenced function has non-fixed values assigned to its parameters.
Let `unused` & `!keep_fnames` do the scanning, then apply `reduce_vars` only to unnamed functions.
fixes#1595
- one-use function call => IIFE should take `eval()` & `arguments` into account
- if unused parameter cannot be eliminated, replace it with `0`
fixes#1583
those were not optimised for `unused` before, which made it necessary for `reduce_vars` to have separate steps for `keep_fnames`
docs update by @kzc
closes#1577
Function expression can be assigned to a variable and be given a name. Ensure function name is the reduced variable before clearing it out.
fixes#1573fixes#1575
`unsafe` turns undefined keyword into a variable of the same name if found, but that interferes with other related optimisations.
Keep track of such transformations to ensure zero information loss in the process.
Bookmarklet for instance implicitedly assumes a "completion value" without using `return`.
The `expression` option now supports such use cases.
Optimisations on IIFEs also enhanced.
fixes#354fixes#543fixes#625fixes#628fixes#640closes#1293
Avoid variable substitution in the following cases:
- use of variable before declaration
- declaration within conditional code blocks
- declaration within loop body
fixes#1518fixes#1525
Patched up `make_node()` without `orig`.
There may be other cases where `start` could be missing, so make it print "undefined" instead of crashing.
fixes#1518
Modules like webpack and grunt-contrib-uglify still uses `ast.transform(compressor)` before `Compressor.compress(ast)` was introduced.
Workaround this compatibility issue by deactivating `reduce_vars` in such case.
Also fix use case with omitted `options` when calling `Compressor()`.
fixes#1516
- Use AST_Destructuring for lhf assignment patterns
- Use AST_DefaultAssign for default assignments
- Add more checks for lhs expressions
- Add lots of testing
- Cleanup ast (e.g. remove default property)
- Fix#1402 based on a patch from @kzc
- Refine spread allowance in array destructring pattern
- Add destructuring AST tree checker
A function call or IIFE with an immediately preceding comment
containing `@__PURE__` or `#__PURE__` is deemed to be a
side-effect-free pure function call and can potentially be
dropped.
Depends on `side_effects` option.
`[#@]__PURE__` hint will be removed from comment when pure
call is dropped.
fixes#1261closes#1448
- support arrays, objects & AST_Node
- support `"a.b":1` on both cli & API
- emit warning if variable is modified
- override top-level variables
fixes#1416closes#1198closes#1469
- remove extra tree scanning phase for `negate_iife`
- `negate_iife` now only deals with the narrowest form, i.e. IIFE sitting directly under `AST_SimpleStatement`
- `booleans`, `conditionals` etc. will now take care the rest via more accurate accounting
- `a(); void b();` => `a(); b();`
fixes#1288closes#1451
- 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
- remove call to evaluate() in is_constant() and let nested optimize() does its job instead
- reject RegExp in is_constant() and remove special case logic under collapse_vars
- operands to conditionals optimisation are now always evaluate()-ed
- throw error in constant_value() instead of returning undefined to catch possible bugs, similar to make_node_from_constant()
- optimise binary boolean operators under `evaluate` instead of `conditionals`
* Fixes#1147: template strings not obeying -b ascii_only true
* Allow evaluation of template expressions by adding optimizers and
walkers
* Make sure tagged templates are never changed
* Remove template tokenizer in parser, add template tokenizer in
tokenizer. It is using a brace counter to track brace position of
templates
* Add tokens `template_head` and `template_substitution` but parsing
tokens stays mostly the same
* Do not output strings anymore in AST_TemplateString, instead use
AST_TemplateSegment
* Fix parsing tagged templates, allowing multiple templates behind
as spec allows this
These changes don't influence tagged templates because raw content
may influence code execution, however they are safe to do in normal
templates:
* Allow basic string concatenation of templates where possible
* Allow custom character escape style similar to strings, except in
tagged templates
Note that expressions are still compressed in tagged templates.
Optional things that may be improved later:
* Custom quote style for templates if it doesn't have expressions.
Making it obey the quote_style option if this is the case.
Has little or no impact on minification size in the majority of
cases but can speed up rollup builds significantly.
This sequences change also has the beneficial side effect of avoiding
"stack size exceeded" errors on very large input files.
The user is free to alter the sequences limit if they are so inclined.
The previous sequences limit was 2000. 20 is often sufficient.
catch identifier is mangled correctly for ES5 standards-compliant JS engines by default.
Unconditionally use the ie8 if/do-while workaround whether or not --screw-ie8 is enabled.
To support non-standard ie8 javascript use: uglifyjs --support-ie8
