jsonc-parser

Scanner and parser for JSON with comments.

# Why?

JSONC is JSON with JavaScript style comments. This node module provides a scanner and fault tolerant parser that can process JSONC but is also useful for standard JSON.

- the scanner tokenizes the input string into tokens and token offsets
- the visit function implements a 'SAX' style parser with callbacks for the encountered properties and values.
- the parseTree function computes a hierarchical DOM with offsets representing the encountered properties and values.
- the parse function evaluates the JavaScript object represented by JSON string in a fault tolerant fashion.
- the getLocation API returns a location object that describes the property or value located at a given offset in a JSON document.
- the findNodeAtLocation API finds the node at a given location path in a JSON DOM.
- the format API computes edits to format a JSON document.
- the modify API computes edits to insert, remove or replace a property or value in a JSON document.
- the applyEdits API applies edits to a document.

# Installation

    npm install --save jsonc-parser

# API

## Scanner:

/**
* Creates a JSON scanner on the given text.
* If ignoreTrivia is set, whitespaces or comments are ignored.
*/
export function createScanner(text:string, ignoreTrivia:boolean = false):JSONScanner;
/**
* The scanner object, representing a JSON scanner at a position in the input string.
*/
export interface JSONScanner {
/**
* Sets the scan position to a new offset. A call to 'scan' is needed to get the first token.
*/
setPosition(pos: number): any;
/**
* Read the next token. Returns the token code.
*/
scan(): SyntaxKind;
/**
* Returns the current scan position, which is after the last read token.
*/
getPosition(): number;
/**
* Returns the last read token.
*/
getToken(): SyntaxKind;
/**
* Returns the last read token value. The value for strings is the decoded string content. For numbers its of type number, for boolean it's true or false.
*/
getTokenValue(): string;
/**
* The start offset of the last read token.
*/
getTokenOffset(): number;
/**
* The length of the last read token.
*/
getTokenLength(): number;
/**
* The zero-based start line number of the last read token.
*/
getTokenStartLine(): number;
/**
* The zero-based start character (column) of the last read token.
*/
getTokenStartCharacter(): number;
/**
* An error code of the last scan.
*/
getTokenError(): ScanError;
}

## Parser:

export interface ParseOptions {
disallowComments?: boolean;
}
/**
* Parses the given text and returns the object the JSON content represents. On invalid input, the parser tries to be as fault tolerant as possible, but still return a result.
* Therefore always check the errors list to find out if the input was valid.
*/
export declare function parse(text: string, errors?: {error: ParseErrorCode;}[], options?: ParseOptions): any;
/**
* Parses the given text and invokes the visitor functions for each object, array and literal reached.
*/
export declare function visit(text: string, visitor: JSONVisitor, options?: ParseOptions): any;
export interface JSONVisitor {
/**
* Invoked when an open brace is encountered and an object is started. The offset and length represent the location of the open brace.
*/
onObjectBegin?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a property is encountered. The offset and length represent the location of the property name.
*/
onObjectProperty?: (property: string, offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a closing brace is encountered and an object is completed. The offset and length represent the location of the closing brace.
*/
onObjectEnd?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when an open bracket is encountered. The offset and length represent the location of the open bracket.
*/
onArrayBegin?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a closing bracket is encountered. The offset and length represent the location of the closing bracket.
*/
onArrayEnd?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a literal value is encountered. The offset and length represent the location of the literal value.
*/
onLiteralValue?: (value: any, offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked when a comma or colon separator is encountered. The offset and length represent the location of the separator.
*/
onSeparator?: (character: string, offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* When comments are allowed, invoked when a line or block comment is encountered. The offset and length represent the location of the comment.
*/
onComment?: (offset: number, length: number, startLine: number, startCharacter: number) => void;
/**
* Invoked on an error.
*/
onError?: (error: ParseErrorCode, offset: number, length: number, startLine: number, startCharacter: number) => void;
}
/**
* Parses the given text and returns a tree representation the JSON content. On invalid input, the parser tries to be as fault tolerant as possible, but still return a result.
*/
export declare function parseTree(text: string, errors?: ParseError[], options?: ParseOptions): Node;
export declare type NodeType = "object" | "array" | "property" | "string" | "number" | "boolean" | "null";
export interface Node {
type: NodeType;
value?: any;
offset: number;
length: number;
colonOffset?: number;
parent?: Node;
children?: Node[];
}

## Utilities:

/**
* Takes JSON with JavaScript-style comments and remove
* them. Optionally replaces every none-newline character
* of comments with a replaceCharacter
*/
export declare function stripComments(text: string, replaceCh?: string): string;
/**
* For a given offset, evaluate the location in the JSON document. Each segment in the location path is either a property name or an array index.
*/
export declare function getLocation(text: string, position: number): Location;
export declare type Segment = string | number;
export interface Location {
/**
* The previous property key or literal value (string, number, boolean or null) or undefined.
*/
previousNode?: Node;
/**
* The path describing the location in the JSON document. The path consists of a sequence strings
* representing an object property or numbers for array indices.
*/
path: Segment[];
/**
* Matches the locations path against a pattern consisting of strings (for properties) and numbers (for array indices).
* '*' will match a single segment, of any property name or index.
* '**' will match a sequece of segments or no segment, of any property name or index.
*/
matches: (patterns: Segment[]) => boolean;
/**
* If set, the location's offset is at a property key.
*/
isAtPropertyKey: boolean;
}
/**
* Finds the node at the given path in a JSON DOM.
*/
export function findNodeAtLocation(root: Node, path: JSONPath): Node | undefined;
/**
* Finds the most inner node at the given offset. If includeRightBound is set, also finds nodes that end at the given offset.
*/
export function findNodeAtOffset(root: Node, offset: number, includeRightBound?: boolean) : Node | undefined;
/**
* Gets the JSON path of the given JSON DOM node
*/
export function getNodePath(node: Node) : JSONPath;
/**
* Evaluates the JavaScript object of the given JSON DOM node
*/
export function getNodeValue(node: Node): any;
/**
* Computes the edits needed to format a JSON document.
*
* @param documentText The input text
* @param range The range to format or `undefined` to format the full content
* @param options The formatting options
* @returns A list of edit operations describing the formatting changes to the original document. Edits can be either inserts, replacements or
* removals of text segments. All offsets refer to the original state of the document. No two edits must change or remove the same range of
* text in the original document. However, multiple edits can have
* the same offset, for example multiple inserts, or an insert followed by a remove or replace. The order in the array defines which edit is applied first.
* To apply edits to an input, you can use `applyEdits`
*/
export function format(documentText: string, range: Range, options: FormattingOptions): Edit[];
/**
* Computes the edits needed to modify a value in the JSON document.
*
* @param documentText The input text
* @param path The path of the value to change. The path represents either to the document root, a property or an array item.
* If the path points to an non-existing property or item, it will be created.
* @param value The new value for the specified property or item. If the value is undefined,
* the property or item will be removed.
* @param options Options
* @returns A list of edit operations describing the formatting changes to the original document. Edits can be either inserts, replacements or
* removals of text segments. All offsets refer to the original state of the document. No two edits must change or remove the same range of
* text in the original document. However, multiple edits can have
* the same offset, for example multiple inserts, or an insert followed by a remove or replace. The order in the array defines which edit is applied first.
* To apply edits to an input, you can use `applyEdits`
*/
export function modify(text: string, path: JSONPath, value: any, options: ModificationOptions): Edit[];
/**
* Applies edits to a input string.
*/
export function applyEdits(text: string, edits: Edit[]): string;
/**
* Represents a text modification
*/
export interface Edit {
/**
* The start offset of the modification.
*/
offset: number;
/**
* The length of the modification. Must not be negative. Empty length represents an *insert*.
*/
length: number;
/**
* The new content. Empty content represents a *remove*.
*/
content: string;
}
/**
* A text range in the document
*/
export interface Range {
/**
* The start offset of the range.
*/
offset: number;
/**
* The length of the range. Must not be negative.
*/
length: number;
}
export interface FormattingOptions {
/**
* If indentation is based on spaces (`insertSpaces` = true), then what is the number of spaces that make an indent?
*/
tabSize: number;
/**
* Is indentation based on spaces?
*/
insertSpaces: boolean;
/**
* The default 'end of line' character
*/
eol: string;
}

# License

(MIT License)

Copyright 2018, Microsoft