jsstana

jsstana

s-expression match patterns for Mozilla Parser AST

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

(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 combinedMatch

(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).

(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

• 0.0.12 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:

* Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the following
  disclaimer in the documentation and/or other materials provided
  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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.