coffee-ast-walk
v1.3.0
Published
Coffeescript AST walker
Maintainers
venkatperiReadme
coffee-ast-walk
Walk Coffeescript's AST nodes
Installation
Install with npm
npm install coffee-ast-walk --saveExamples
Create a ast walker
astwalk = require 'coffee-ast-walk'
root = coffee.nodes source
walk = astwalk(root)Dump Every Node
walk.walk (x) ->
console.log x AST Node Count
walk.reduce 0, (x, acc) ->
if @isAstNode then acc + 1 else accFind the First Class
walk.findFirstByType 'Class'Get Parent of Type
klass = walk.findFirstByType 'Class'
# fire up another walker
astwalk(klass).findParent ( x ) -> x.__type is 'Assign'AST Node Meta Information
astwalk adds a property meta to Base which is the base class for Coffeescript AST node classes. meta provides meta-information about the node and in many cases, it rolls up information from child nodes which can ease navigation and maipulation of the AST. See API for more details on the meta object.
API
Create Walker
astwalk(node[, init])
Returns a walker. astwalk . Setting init will perform an initial walk over the AST tree and append a meta object as well as two properties to each AST node:
__idA unique id (monotonically increasing count).__typeThe type of AST node (node.constructor.name)
Methods
walk([context, ] visitor)
walkToDepth([context, ] [depth, ] visitor)
Walk's the AST tree and invokes the visitor for each node. Context is an optional {Object} which is available to the visitor callback. Providing depth will limit the walk up to depth nodes from the current node (i.e. relative to the current node).
About the Visitor: visitor(node)
The current node is passed ot the visitor. Additionaly, the following properties are available in the this context of the visitor callback:
@pathThepathto the current node as an array of strings.@depthThe depth of the current node.@isRootTrue if the node is the root node.@isLeafTrue of the node is a leaf node.@idTheidused to invoke the current node, also the last element of the path array.@isAstNodeTrue if the node is a coffeescript AST node, or a scalar (string etc).@contextAn optional context, passed to walk.@parentThe node's parent (undefined for root node).
The visitor callback can invoke @abort() to terminate the walk early.
Return Value: If a visitor returns an {Object}, the values from visiting the current AST node's child nodes are added to the object with the same key names as the original node. This can be viewed as a mapping operation on the AST tree (see example at the end).
findAll([depth, ] f(node))
Returns all nodes (unto to optional depth) that satisfy the callback f.
findFirst([depth, ] f(node)
Returns the first node (limited by depth) that matches the callback f.
findByType(type[, depth])
Returns a list of nodes with the given {String} type, up to optional depth.
findFirstByType(type[, depth])
Returns the first node with the given {String} type, up to optional depth.
reduce([initial,] f)
Updates an internal accumulator to the value returned by f(node, acc) and returns the final value of acc. The accumulator is optionally set to initial.
findParent(pred)
Returns the closes ancestor that satisfies the supplied predicate pred.
findParentByType(type)
Returns the closest ancestor with the given type.
up(f)
Walks up the ancestor list and invokes the given callback f .
Meta Object
node.meta is a custom property is added to Coffeescript AST nodes. The following properties are available on all meta objects:
@nodeThe original AST node.@pathThepathto the current node as an array of strings.@depthThe depth of the current node.@isRootTrue if the node is the root node.@isLeafTrue of the node is a leaf node.@idA unique id assigned to each id. Not the same as theidavailable during a walk. Same asnode.__id.@isAstNodeTrue if the node is a coffeescript AST node, or a scalar (string etc).@parentThe node's parent (undefined for root node).
In addition, the following context-sensitive (i.e. node type) properties are available on node.meta:
name- for
Class, the class name. - for
Assign, thelhsof the assignment operator. - for
Param, the parameter name
- for
value- for
Comment, the comment string - for
Param, the param's value - for
Assign, therhsof the assignment - for
Literal, the value of the literal - for
Access, the qualified name (e.g.module.exports) - for
Value, the value
- for
logicalItem- forAssignnodes, returns therhsof the assignment since it the logical basis for interpreting theAssignnode sub-tree.superClassthe name of the class' super class, if anyclassMembers, for classes, returns an object withstaticandinstancemembers. Members which are methods also include parameter information.methodParamsreturns an array or parameters for methods.
Example - AST Tree View
Map the AST tree to a human readable JSON object and use the treeify module to display it as a tree.
walk = astwalk(ast, true)
res = walk.walk ( x ) ->
o = {}
for t in [ 'type', 'name', 'value' ]
v = x.meta?[ t ]
o[ t ] = v if v and !_.isObjectLike v
o
console.log treeify.asTree res, trueLet's apply it to this coffeescript:
###
# Base class for all animals.
#
# @example How to subclass an animal
# class Lion extends Animal
# move: (direction, speed): ->
#
###
module.exports = class Example.Animal
###
# The Answer to the Ultimate Question of Life, the Universe, and Everything
###
@ANSWER = 42
@create: ->
###
# @property [Array<String>] the nicknames
###
nicknames : []
###
Construct a new animal.
@param [String] name the name of the animal
@param [Date] birthDate when the animal was born
###
constructor : ( @type, @name, @birthDate = new Date() ) ->
###
Move the animal.
@example Move an animal
new Lion('Simba').move('south', 12)
@param [Object] options the moving options
@option options [String] direction the moving direction
@option options [Number] speed the speed in mph
@public
###
move : ( options = {} ) ->
class Tiger extends Example.Animal
constructor : ( {@striped}, abc )->
super 'Tiger'
module.exports = TigerAnd the tree view:
├─ type: Block
└─ expressions
├─ 0
│ ├─ type: Comment
│ └─ value:
# Base class for all animals.
#
# @example How to subclass an animal
# class Lion extends Animal
# move: (direction, speed): ->
#
├─ 1
│ ├─ type: Assign
│ ├─ name: module.exports
│ ├─ variable
│ │ ├─ type: Value
│ │ ├─ value: module.exports
│ │ ├─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: module
│ │ └─ properties
│ │ └─ 0
│ │ ├─ type: Access
│ │ ├─ value: .exports
│ │ └─ name
│ │ ├─ type: Literal
│ │ └─ value: exports
│ └─ value
│ ├─ type: Class
│ ├─ name: Example.Animal
│ ├─ variable
│ │ ├─ type: Value
│ │ ├─ value: Example.Animal
│ │ ├─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: Example
│ │ └─ properties
│ │ └─ 0
│ │ ├─ type: Access
│ │ ├─ value: .Animal
│ │ └─ name
│ │ ├─ type: Literal
│ │ └─ value: Animal
│ └─ body
│ ├─ type: Block
│ └─ expressions
│ ├─ 0
│ │ ├─ type: Comment
│ │ └─ value:
# The Answer to the Ultimate Question of Life, the Universe, and Everything
│ ├─ 1
│ │ ├─ type: Assign
│ │ ├─ name: this.ANSWER
│ │ ├─ value
│ │ │ ├─ type: Value
│ │ │ ├─ value: 42
│ │ │ └─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: 42
│ │ └─ variable
│ │ ├─ type: Value
│ │ ├─ value: this.ANSWER
│ │ ├─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: this
│ │ └─ properties
│ │ └─ 0
│ │ ├─ type: Access
│ │ ├─ value: .ANSWER
│ │ └─ name
│ │ ├─ type: Literal
│ │ └─ value: ANSWER
│ └─ 2
│ ├─ type: Value
│ └─ base
│ ├─ type: Obj
│ └─ properties
│ ├─ 0
│ │ ├─ type: Assign
│ │ ├─ name: this.create
│ │ ├─ variable
│ │ │ ├─ type: Value
│ │ │ ├─ value: this.create
│ │ │ ├─ base
│ │ │ │ ├─ type: Literal
│ │ │ │ └─ value: this
│ │ │ └─ properties
│ │ │ └─ 0
│ │ │ ├─ type: Access
│ │ │ ├─ value: .create
│ │ │ └─ name
│ │ │ ├─ type: Literal
│ │ │ └─ value: create
│ │ ├─ value
│ │ │ ├─ type: Code
│ │ │ └─ body
│ │ │ └─ type: Block
│ │ └─ operatorToken
│ │ ├─ type: Literal
│ │ └─ value: :
│ ├─ 1
│ │ ├─ type: Comment
│ │ └─ value:
# @property [Array<String>] the nicknames
│ ├─ 2
│ │ ├─ type: Assign
│ │ ├─ name: nicknames
│ │ ├─ variable
│ │ │ ├─ type: Value
│ │ │ ├─ value: nicknames
│ │ │ └─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: nicknames
│ │ ├─ value
│ │ │ ├─ type: Value
│ │ │ └─ base
│ │ │ └─ type: Arr
│ │ └─ operatorToken
│ │ ├─ type: Literal
│ │ └─ value: :
│ ├─ 3
│ │ ├─ type: Comment
│ │ └─ value:
Construct a new animal.
@param [String] name the name of the animal
@param [Date] birthDate when the animal was born
│ ├─ 4
│ │ ├─ type: Assign
│ │ ├─ name: constructor
│ │ ├─ variable
│ │ │ ├─ type: Value
│ │ │ ├─ value: constructor
│ │ │ └─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: constructor
│ │ ├─ value
│ │ │ ├─ type: Code
│ │ │ ├─ params
│ │ │ │ ├─ 0
│ │ │ │ │ ├─ type: Param
│ │ │ │ │ └─ name
│ │ │ │ │ ├─ type: Value
│ │ │ │ │ ├─ value: this.type
│ │ │ │ │ ├─ base
│ │ │ │ │ │ ├─ type: Literal
│ │ │ │ │ │ └─ value: this
│ │ │ │ │ └─ properties
│ │ │ │ │ └─ 0
│ │ │ │ │ ├─ type: Access
│ │ │ │ │ ├─ value: .type
│ │ │ │ │ └─ name
│ │ │ │ │ ├─ type: Literal
│ │ │ │ │ └─ value: type
│ │ │ │ ├─ 1
│ │ │ │ │ ├─ type: Param
│ │ │ │ │ └─ name
│ │ │ │ │ ├─ type: Value
│ │ │ │ │ ├─ value: this.name
│ │ │ │ │ ├─ base
│ │ │ │ │ │ ├─ type: Literal
│ │ │ │ │ │ └─ value: this
│ │ │ │ │ └─ properties
│ │ │ │ │ └─ 0
│ │ │ │ │ ├─ type: Access
│ │ │ │ │ ├─ value: .name
│ │ │ │ │ └─ name
│ │ │ │ │ ├─ type: Literal
│ │ │ │ │ └─ value: name
│ │ │ │ └─ 2
│ │ │ │ ├─ type: Param
│ │ │ │ ├─ name
│ │ │ │ │ ├─ type: Value
│ │ │ │ │ ├─ value: this.birthDate
│ │ │ │ │ ├─ base
│ │ │ │ │ │ ├─ type: Literal
│ │ │ │ │ │ └─ value: this
│ │ │ │ │ └─ properties
│ │ │ │ │ └─ 0
│ │ │ │ │ ├─ type: Access
│ │ │ │ │ ├─ value: .birthDate
│ │ │ │ │ └─ name
│ │ │ │ │ ├─ type: Literal
│ │ │ │ │ └─ value: birthDate
│ │ │ │ └─ value
│ │ │ │ ├─ type: Call
│ │ │ │ └─ variable
│ │ │ │ ├─ type: Value
│ │ │ │ ├─ value: Date
│ │ │ │ └─ base
│ │ │ │ ├─ type: Literal
│ │ │ │ └─ value: Date
│ │ │ └─ body
│ │ │ ├─ type: Block
│ │ │ └─ expressions
│ │ │ └─ 0
│ │ │ ├─ type: Comment
│ │ │ └─ value:
Move the animal.
@example Move an animal
new Lion('Simba').move('south', 12)
@param [Object] options the moving options
@option options [String] direction the moving direction
@option options [Number] speed the speed in mph
@public
│ │ └─ operatorToken
│ │ ├─ type: Literal
│ │ └─ value: :
│ └─ 5
│ ├─ type: Assign
│ ├─ name: move
│ ├─ variable
│ │ ├─ type: Value
│ │ ├─ value: move
│ │ └─ base
│ │ ├─ type: Literal
│ │ └─ value: move
│ ├─ value
│ │ ├─ type: Code
│ │ ├─ params
│ │ │ └─ 0
│ │ │ ├─ type: Param
│ │ │ ├─ name
│ │ │ │ ├─ type: Literal
│ │ │ │ └─ value: options
│ │ │ └─ value
│ │ │ ├─ type: Value
│ │ │ └─ base
│ │ │ └─ type: Obj
│ │ └─ body
│ │ └─ type: Block
│ └─ operatorToken
│ ├─ type: Literal
│ └─ value: :
├─ 2
│ ├─ type: Class
│ ├─ name: Tiger
│ ├─ variable
│ │ ├─ type: Value
│ │ ├─ value: Tiger
│ │ └─ base
│ │ ├─ type: Literal
│ │ └─ value: Tiger
│ ├─ parent
│ │ ├─ type: Value
│ │ ├─ value: Example.Animal
│ │ ├─ base
│ │ │ ├─ type: Literal
│ │ │ └─ value: Example
│ │ └─ properties
│ │ └─ 0
│ │ ├─ type: Access
│ │ ├─ value: .Animal
│ │ └─ name
│ │ ├─ type: Literal
│ │ └─ value: Animal
│ └─ body
│ ├─ type: Block
│ └─ expressions
│ └─ 0
│ ├─ type: Value
│ └─ base
│ ├─ type: Obj
│ └─ properties
│ └─ 0
│ ├─ type: Assign
│ ├─ name: constructor
│ ├─ variable
│ │ ├─ type: Value
│ │ ├─ value: constructor
│ │ └─ base
│ │ ├─ type: Literal
│ │ └─ value: constructor
│ ├─ value
│ │ ├─ type: Code
│ │ ├─ params
│ │ │ ├─ 0
│ │ │ │ ├─ type: Param
│ │ │ │ └─ name
│ │ │ │ ├─ type: Obj
│ │ │ │ └─ properties
│ │ │ │ └─ 0
│ │ │ │ ├─ type: Value
│ │ │ │ ├─ value: this.striped
│ │ │ │ ├─ base
│ │ │ │ │ ├─ type: Literal
│ │ │ │ │ └─ value: this
│ │ │ │ └─ properties
│ │ │ │ └─ 0
│ │ │ │ ├─ type: Access
│ │ │ │ ├─ value: .striped
│ │ │ │ └─ name
│ │ │ │ ├─ type: Literal
│ │ │ │ └─ value: striped
│ │ │ └─ 1
│ │ │ ├─ type: Param
│ │ │ └─ name
│ │ │ ├─ type: Literal
│ │ │ └─ value: abc
│ │ └─ body
│ │ ├─ type: Block
│ │ └─ expressions
│ │ └─ 0
│ │ ├─ type: Call
│ │ └─ args
│ │ └─ 0
│ │ ├─ type: Value
│ │ ├─ value: 'Tiger'
│ │ └─ base
│ │ ├─ type: Literal
│ │ └─ value: 'Tiger'
│ └─ operatorToken
│ ├─ type: Literal
│ └─ value: :
└─ 3
├─ type: Assign
├─ name: module.exports
├─ value
│ ├─ type: Value
│ ├─ value: Tiger
│ └─ base
│ ├─ type: Literal
│ └─ value: Tiger
└─ variable
├─ type: Value
├─ value: module.exports
├─ base
│ ├─ type: Literal
│ └─ value: module
└─ properties
└─ 0
├─ type: Access
├─ value: .exports
└─ name
├─ type: Literal
└─ value: exports