jsstana

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

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

# 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.

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.

(nor pattern) and (nand pattern)

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 . ?) or similar dotted list syntax.

(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
• (undefined) - matches undefined

(return value)

Matches ReturnStatement.

(expression expr)

Matches expression statement, ExpressionStatement.

(throw ex)

Matches ThrowStatement.

(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.

API

match(pattern, node)

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.

createMatcher(pattern, [posMatcher])

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

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

new jsstana()

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

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

• 0.0.15 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

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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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