asty

ASTy
====

Abstract Syntax Tree (AST) Data Structure




Installation
------------

``shell
$ npm install asty
`

About
-----

ASTy is a Abstract Syntax Tree (AST) Data Structure library for JavaScript,
i.e., it provides a hierarchical data structure for holding the syntax
abstraction of an arbitrary formal language. It is usually used
in combination with a parser generator like PEG.js
(and then especially with its utility class PEGUtil)
to carry the results of the parsing step and to provide the vehicle
for further processing those results.

Usage
-----

ASTy provides a context (ASTYCtx below) for the creation of AST node
(ASTYNode below). The tree of AST nodes is formed by linking child
AST nodes into a parent AST node. The ASTy API, here assumed to be
exposed through the variable ASTY, provides the following methods (in
a notation somewhat resembling TypeScript type definitions):

$3

- new ASTY(): ASTYCtx:

Create a new instance of the ASTy context.
It internally captures the prototype (ASTYNode) of the AST nodes to be created.

- ASTYCtx#version(): { major: Number, minor: Number, micro: Number, date: Number }:

Return the ASTy version detals. The date is in numeric format YYYYMMDD.

- ASTYCtx#extend(object: { [methodName: String]: [methodFunc: Function] }): ASTYCtx:

Extend the internal ASTYNode prototype with additional methods which are then available on each
ASTYNode instance when created with ASTYCtx#create. This should be used by ASTy extension modules only.

- ASTYCtx#create(type: String, attrs?: {[name: String]: [value: Object]}, childs?: ASTY[]): ASTYNode:

Create a new ASTYNode instance of type and optionally already set attributes and add child nodes.

- ASTYCtx#isA(object: Object): Boolean:

Check whether object is an ASTYNode instance.

- static ASTYCtx::serialize(node: ASTYNode): String:

Serializes (formats) ASTy nodes to JSON string. Use this for exporting an AST.

- static ASTYCtx::unserialize(json: String): ASTYNode:

Unserializes (parses) JSON string to ASTy nodes. Use this for importing an AST.

$3

- ASTYNode#create(type: String, attrs?: {[name: String]: [value: Object]}, childs?: ASTY[]): ASTYNode:

Create a new ASTYNode instance of type and optionally already set attributes and add child nodes.

- ASTYNode#merge(node: Node, takePos?: Boolean, attrMap?: {[from: String]: [to: (String|null)})): ASTYNode:

Merge attributes, childs and optionally the position of a node.
The attributes can be renamed or skipped (if mapped onto null).

- ASTYNode#type(type: String): Boolean:

ASTYNode#type(): String:

Set or get type of node.

- ASTYNode#pos(line: Number, column: Number, offset: Number): ASTYNode:

ASTYNode#pos(): { line: Number, column: Number, offset: Number }:

Set or get the position for the node.

- ASTYNode#set(name: String, value: Object): ASTYNode:

ASTYNode#set({ [String]: Object }): ASTYNode:

Set a single attribute name to value or set multiple
attributes to their corresponding value.

- ASTYNode#unset(name: String): ASTYNode:

ASTYNode#unset(names: String[]): ASTYNode:

Unset a single attribute name or unset multiple attributes.

- ASTYNode#set({ [name: String]: [value: Object] }): ASTYNode:

Set multiple attributes, each consisting of name and value pairs.

- ASTYNode#get(name: String): Object:

ASTYNode#get(names: String[]): Object[]:

Get value of a particular attribute name,
or get array of values corresponding to each name in names.

- ASTYNode#attrs(): String[]:

Get names of all node attributes.

- ASTYNode#nth(): Number:

Get position among sibling nodes in parent's child node list.
The positions start at 0.

- ASTYNode#ins(pos: Number, childs: ASTYNode[]): ASTYNode:

Add one or more childs to a node, at a fixed position pos. The array childs
can either contain ASTYNode objects or even arrays of ASTYNode objects.
If pos is negative it counts from the end of child list,
with -1 the position after the last existing child.

- ASTYNode#add(childs: ASTYNode[]): ASTYNode:

Add one or more childs to a node, at the end of the child list. The array childs
can either contain ASTYNode objects or even arrays of ASTYNode objects.

- ASTYNode#del(childs: ASTYNode[]): ASTYNode:

Delete one or more childs from a node.

- ASTYNode#childs(begin?: Number, end?: Number): ASTYNode[]:

Get a nodes list of all or some childs. The begin and end parameters
are passed-through to Array::slice. If the range from begin to end is
out of range, an empty array is returned.

- ASTYNode#child(pos: Number): ASTYNode:

Get a particular child node. If pos is out of range, null is returned.

- ASTYNode#parent(): ASTYNode:

Get parent node.

- ASTYNode#walk(callback: (node: ASTYNode, depth: Number, parent: ASTYNode, when: String) => Void, when?: String): ASTYNode:

Recursively walk the AST starting at this node (at depth 0). For
each visited node the callback function is called with the
current node, the current node's tree depth, the current node's
parent node and the current walking situation. By default (and
if when is either downward or both), the callback is called
in the downward phase, i.e., before(!) all child nodes will be
visited, and with when set to downward. If when is set to
upward or both, the callback is called in the upward phase,
i.e., after(!) all child nodes were visited, and with when set
to upward.

- ASTYNode#dump(maxDepth?: Number, colorize?: (type: String, text: String) => String, unicode?: Boolean): String:

Returns a textual dump of the AST starting at the current node. By
default maxDepth is Infinity and this way the whole AST below the
current node is dumped. If maxDepth is 0 only the current node is
dumped. If maxDepth is 1 the current node and all its direct child
nodes are dumped. The parameter colorize is an optional callback function,
intended to colorize the output text fragments according to their type.
The following type strings are supported: tree, type, parenthesis, comma,
key, colon, value, position, bracket, line, slash, and column.
If unicode is set to false, ASCII substitution characters are used
for the tree structure.

- ASTYNode#serialize(): String:

Recursively serializes the AST node to JSON.
Use this for exporting.

Implementation Notice
---------------------

Although ASTy is written in ECMAScript 2018, it is transpiled to older
environments and this way runs in really all current (as of 2018)
JavaScript environments, of course.

Additionally, there are two transpilation results: first, there is a
compressed asty.browser.js for Browser environments. Second, there is
an uncompressed asty.node.js` for Node.js environments.

Alternatives
------------

A few decent alternatives to ASTy exist:

- UniST and UniST Builder
- estree
- AST-Types

License
-------

Copyright © 2014-2024 Dr. Ralf S. Engelschall (http://engelschall.com/)

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.