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6 commits

Author SHA1 Message Date
thiemowmde 24888bea15 Mark protected stuff in classes with no subclasses as private
Protected effectively means "public to subclasses" and should be
avoided for the same reasons as marking everything as public should
be avoided.

Change-Id: Iba674b486ce53fd1f94f70163d47824e969abb77
2023-06-23 12:28:06 +02:00
Thiemo Kreuz bbded6231c Inline/simplify smaller pieces of duplicate/complex PHP code
Change-Id: I59d0f17b77c8c3d47bc532bdefd9d8c0883f180b
2022-06-03 21:04:38 +02:00
Thiemo Kreuz a25e2c784a Fix capitalization of method calls accross the codebase
Change-Id: Icbbad4858735c24611daee693c53af479c75d1fb
2022-04-26 17:42:34 +02:00
Daimona Eaytoy f8e9ac7e2a Rename AbuseFilterCachingParser -> FilterEvaluator
It's an evaluator, not a parser.

Change-Id: Ib6d33e8423ea72709cf5a33f4397ba33e352ea80
2021-09-08 13:40:47 +02:00
Daimona Eaytoy 6684ea6450 Remove AFPTransitionBase
Also cleanup the mPos hack in the CachingParser.

Change-Id: Ib5693802a3ceb80cb736880ed65e27340abef689
2021-09-06 19:33:48 +00:00
Sorawee Porncharoenwase 320e3d696f Add a static analyzer for the filter language
This commit adds a class AFPSyntaxChecker which can statically analyze
a filter code to detect the following errors:

- unbound variables (which comes in two modes: conservative and liberal,
  default to conservative)
- unused variables (disabled by default for compatibilty)
- assignment on built-in identifiers
- function application's arity mismatch
- function application's invalid function name
- non-string literal in the first argument of set / set_var

The existing parser and evaluator are modified as follows:

- The new (caching) evaluator no longer needs to perform variable
  hoisting at runtime.
  - Note that for array assignment, this changes the semantics.
- The new parser is more lenient, reducing parsing errors.
  The static analyzer will catch these errors instead, allowing us
  to give a much better error message and reduces the complexity of
  the parser.
  * The parser now allows function name to be any identifier.
  * The parser now allows arity mismatch to occur.
  * The parser now allows the first argument of set to be any expression.

Concretely, obvious changes that users will see are:

1. a := [1]; false & (a[] := 2); a[0] === 1

   would evaluate to true, while it used to evaluate to the undefined value
   due to hoisting

2. f(1)

   will now error with 'f is not a valid function' as opposed to
   'Unexpected "T_BRACE"'

3. length

   will now error with 'Illegal use of built-in identifier "length"'
   as opposed to 'Expected a ('

Appendix: conservative and liberal mode

The conservative mode is completely compatible with the current evaluator.
That is,

false & (a := 1); a

will not deem `a` as unbound, though this is actually undesirable because
`a` would then be bound to the troublesome undefined value.

The liberal mode rejects the above pattern by deeming `a` as unbound.
However, it also rejects

true & (a := 1); a

even though (a := 1) is always executed. Since there are several filters
in Wikimedia projects that rely on this behavior, we default the mode
to conservative for now.

Note that even the liberal mode doesn't really respect lexical scope
appeared in some other programming languages (see also T234690).
For instance:

(if true then (a := 1) else (a := 2) end); a

would be accepted by the liberal checker, even though under lexical scope,
`a` would be unbound. However, it is unlikely that lexical scope
will be suitable for the filter language, as most filters in
Wikimedia projects that have user-defined variable do violate lexical scope.

Bug: T260903
Bug: T238709
Bug: T237610
Bug: T234690
Bug: T231536
Change-Id: Ic6d030503e554933f8d220c6f87b680505918ae2
2021-08-31 03:28:24 +02:00