jsstana

> s-expression match patterns for Mozilla Parser AST

jsstana will help you to find exactly the code snippet you are searching for.
It's much more precise than using grep.


Synopsis

``javascript
var jsstana = require("jsstana");
var esprima = require("esprima");

var contents = // ...
var syntax = esprima.parse(contents);

jsstana.traverse(syntax, function (node) {
var m = jsstana.match("(call alert ?argument)", node);
if (m) {
console.log("alert called with argument", m.argument);
}
});
`

jsgrep

The jsgrep example utility is provided

`bash


find assertArguments calls with 4 arguments


% jsgrep '(call ?.assertArguments ? ? ? ?)' lib
matchers/literal.js:25: this.assertArguments("true/false/null/infinity/nan/undefined", 0, arguments, 1);
matchers/literal.js:111: this.assertArguments("literal", 1, arguments, 1);
matchers/member.js:18: that.assertArguments("member/property/subscript", 2, arguments, 1);
matchers/operator.js:63: that.assertArguments(ratorName, 3, arguments, 3);
matchers/operator.js:98: that.assertArguments("unary", 2, arguments, 1);
matchers/operator.js:128: that.assertArguments("update/postfix/prefix", 2, arguments, 1);
matchers/simple.js:7: this.assertArguments(rator, 1, arguments, 3);
`

Pattern syntax

#### (?name pattern)

Gives pattern a name, so matching node is also captured.

`js
jsstana.match("(binary ?op ?lhs (?rhs (or (literal) (ident))))");
`

#### (not pattern)

Matches when pattern doesn't match.

#### (or pattern1 pattern2...)

Matches if any pattern matches, returns first match.

#### (and pattern1 pattern2...)

Matches if all pattern matches, returns combined match.

$3

Are the same as (not (or pattern)) and (not (and pattern)) respectively.

#### (call callee arg0...argn)

Matches CallExpression.

(call fun arg1 arg2) matches exact amount of arguments,
for arbitrary arguments use
(call fun ??params)

#### (new class arg0...argn)

Matches NewExpression.

#### (ident name)

Matches Identifier.

#### (var name init)

Matches VariableDeclarator.

#### (null-node)

Matches undefined node.

#### (literal value)

Matches Literal.

There are some additional version::

- (string value) - string values
- (number value) - number values
- (bool value) - boolean values
- (regexp value) - regular expressions
- (true) - matches true
- (false) - matches false
- (null) - matches null
- (infinity) - matches Infinity
- (nan) - matches NaN, also (NaN) is supported
- (undefined) - matches undefined, also (Infinity) is supported

#### (this)

Matches ThisExpression.

#### (return value)

Matches ReturnStatement.

#### (expression expr)

Matches expression statement, ExpressionStatement.

#### (throw ex)

Matches ThrowStatement.

#### (break)

Matches BreakStatement.

#### (continue)

Matches ContinueStatement.

#### (member object property)

Matches MemberExpression.

- (property object property) matches non computed expressions, i.e. foo.bar.
- (subscript object property) matches computed expressions i.e. foo[bar].

#### (lookup var.sub.name)

Helper macro for nested variable access.
(lookup foo.bar.baz) is equivalent to (property (property foo bar) baz).

The atom foo.bar.baz works as (lookup foo.bar.baz).

#### (binary op lhs rhs)

Matches BinaryExpression.

Also shorthand syntax is supported, (+ a b) is the same as (binary + a b).

#### (logical op lhs rhs)

Matches LogicalExpression. ie. && and || operators.

#### (unary op value)

Matches UnaryExpression.

Also shorthand version works for ! and ~: (~ ?foo) is the same as (unary ~ ?foo).

#### (update op value)

Matches UpdateExpression.

You might want to use postfix and prefix though.

#### (assign op var value)

Matches AssignmentExpression.

#### (ternary test con alt)

Matches ConditionalExpression.

#### (fn-expr)

Matches FunctionExpression.

#### (object)

Matches ObjectExpression.

API

$3

Match node against pattern.
If pattern matches returns an object with match captures.
Otherwise returns undefined.

This function is autocurried ie. when one argument is passed, returns function node -> matchresult.

This function is also memoized on the pattern, ie each pattern is compiled only once.

$3

Create matcher. With one argument, matcher(pattern) === match(pattern).
With additional arguments, you can add $0, $1... additional anonymous matchers.

`js
var matcher = jsstana.createMatcher("(expr (= a $0))", function (node) {
return node.type === "ObjectExpression" && node.properties.length === 0 ? {} : undefined;
});
`

$3

$3

Create new jsstana context. You can add new operations to this one.

`js
var ctx = new jsstana();
ctx.addMatchers("empty-object", function () {
this.assertArguments("empty-object", 0, arguments);
return function (node) {
return node.type === "ObjectExpression" && node.properties.length === 0 ? {} : undefined;
};
});
ctx.match("(empty-object", node);
`

You may compile submatchers with this.matcher(sexpr) and combine their results with this.combineMatches.
this.assertArguments checks argument (rator) count, to help validate pattern grammar.

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style.

- Add unit tests for any new or changed functionality.
- Lint and test your code using Grunt.
- Use istanbul cover grunt simplemocha to run tests with coverage with istanbul.
- Create a pull request

Release History

- 0.1.6 — 2015-08-28 — Depdenency update
- 0.1.5 — 2014-02-25 — Dependency bump
- 0.1.4 — 2014-11-09 – jsstana.eslintRule
- (object) matcher
- 0.1.3 Multiple multi-param matching groups in (call)

Example: (call ? ?? 0 ??) checks whether function has zero as any argument.

- 0.1.2 Fix bug, identifier could start with underscore: _
- 0.1.1 New (call) syntax
- (call ?fun ?param ?params ?last-one)
- 0.0.22 dependency updates
- 0.0.21 Use commander
- 0.0.20 dependency update
- 0.0.19 dependency updates
- 0.0.18 null checks
- Also updated dependencies
- 0.0.17 this, break & continue
- Added forementioned matchers
- 0.0.16 Updates
- Dependencies updated
- fn-expr matches function expressions
- 0.0.15 Updates
- Dependencies updated
- Introduce eslint
- Fix logical expressions: && and ||
- 0.0.14 Better cli experience
- Strip shebang by default
- Truncate long output lines
- Fancier colorize of jsgrep output
- Catch parse errors and unexisting files
- 0.0.13 nand, nor and ?
- node capturing
- nand and nor
- instanceof, typeof, delete and void operators
- 0.0.12 Code reogranization
- 0.0.11 User-provided patterns
- fixed installing on Windows
- assignment pattern
- anonymous matchers
- 0.0.10 ident pattern
- 0.0.9 Boolean patterns
- 0.0.8 Even more rands
- unary and update expressions
- drop literal- prefix (eg plain string now)
- shorthand binary op syntax (+ a b)`
- shorthand lookup syntax
- 0.0.7 jsgrep, third try
- 0.0.6 jsgrep, second try
- 0.0.5 jsgrep
- also new expression
- 0.0.4 Binary and throw
- 0.0.3 More rands
- call dotted syntax
- literals
- expr - expression statement
- use grunt-literate to generate README.md
- 0.0.2 Dev setup
- 0.0.1 Preview release

Copyright Oleg Grenrus 2013

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

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notice, this list of conditions and the following disclaimer.

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with the distribution.

* Neither the name of Oleg Grenrus nor the names of other
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.

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