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gecko-dev/toolkit/devtools/pretty-fast/pretty-fast.js

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JavaScript
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/*
* Copyright 2013 Mozilla Foundation and contributors
* Licensed under the New BSD license. See LICENSE.md or:
* http://opensource.org/licenses/BSD-2-Clause
*/
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
define(factory);
} else if (typeof exports === 'object') {
module.exports = factory();
} else {
root.prettyFast = factory();
}
}(this, function () {
"use strict";
var acorn = this.acorn || require("acorn/acorn");
var sourceMap = this.sourceMap || require("source-map");
var SourceNode = sourceMap.SourceNode;
// If any of these tokens are seen before a "[" token, we know that "[" token
// is the start of an array literal, rather than a property access.
//
// The only exception is "}", which would need to be disambiguated by
// parsing. The majority of the time, an open bracket following a closing
// curly is going to be an array literal, so we brush the complication under
// the rug, and handle the ambiguity by always assuming that it will be an
// array literal.
var PRE_ARRAY_LITERAL_TOKENS = {
"typeof": true,
"void": true,
"delete": true,
"case": true,
"do": true,
"=": true,
"in": true,
"{": true,
"*": true,
"/": true,
"%": true,
"else": true,
";": true,
"++": true,
"--": true,
"+": true,
"-": true,
"~": true,
"!": true,
":": true,
"?": true,
">>": true,
">>>": true,
"<<": true,
"||": true,
"&&": true,
"<": true,
">": true,
"<=": true,
">=": true,
"instanceof": true,
"&": true,
"^": true,
"|": true,
"==": true,
"!=": true,
"===": true,
"!==": true,
",": true,
"}": true
};
/**
* Determines if we think that the given token starts an array literal.
*
* @param Object token
* The token we want to determine if it is an array literal.
* @param Object lastToken
* The last token we added to the pretty printed results.
*
* @returns Boolean
* True if we believe it is an array literal, false otherwise.
*/
function isArrayLiteral(token, lastToken) {
if (token.type.type != "[") {
return false;
}
if (!lastToken) {
return true;
}
if (lastToken.type.isAssign) {
return true;
}
return !!PRE_ARRAY_LITERAL_TOKENS[lastToken.type.keyword || lastToken.type.type];
}
// If any of these tokens are followed by a token on a new line, we know that
// ASI cannot happen.
var PREVENT_ASI_AFTER_TOKENS = {
// Binary operators
"*": true,
"/": true,
"%": true,
"+": true,
"-": true,
"<<": true,
">>": true,
">>>": true,
"<": true,
">": true,
"<=": true,
">=": true,
"instanceof": true,
"in": true,
"==": true,
"!=": true,
"===": true,
"!==": true,
"&": true,
"^": true,
"|": true,
"&&": true,
"||": true,
",": true,
".": true,
"=": true,
"*=": true,
"/=": true,
"%=": true,
"+=": true,
"-=": true,
"<<=": true,
">>=": true,
">>>=": true,
"&=": true,
"^=": true,
"|=": true,
// Unary operators
"delete": true,
"void": true,
"typeof": true,
"~": true,
"!": true,
"new": true,
// Function calls and grouped expressions
"(": true
};
// If any of these tokens are on a line after the token before it, we know
// that ASI cannot happen.
var PREVENT_ASI_BEFORE_TOKENS = {
// Binary operators
"*": true,
"/": true,
"%": true,
"<<": true,
">>": true,
">>>": true,
"<": true,
">": true,
"<=": true,
">=": true,
"instanceof": true,
"in": true,
"==": true,
"!=": true,
"===": true,
"!==": true,
"&": true,
"^": true,
"|": true,
"&&": true,
"||": true,
",": true,
".": true,
"=": true,
"*=": true,
"/=": true,
"%=": true,
"+=": true,
"-=": true,
"<<=": true,
">>=": true,
">>>=": true,
"&=": true,
"^=": true,
"|=": true,
// Function calls
"(": true
};
/**
* Determines if Automatic Semicolon Insertion (ASI) occurs between these
* tokens.
*
* @param Object token
* The current token.
* @param Object lastToken
* The last token we added to the pretty printed results.
*
* @returns Boolean
* True if we believe ASI occurs.
*/
function isASI(token, lastToken) {
if (!lastToken) {
return false;
}
if (token.startLoc.line === lastToken.startLoc.line) {
return false;
}
if (PREVENT_ASI_AFTER_TOKENS[lastToken.type.type || lastToken.type.keyword]) {
return false;
}
if (PREVENT_ASI_BEFORE_TOKENS[token.type.type || token.type.keyword]) {
return false;
}
return true;
}
/**
* Determine if we have encountered a getter or setter.
*
* @param Object token
* The current token. If this is a getter or setter, it would be the
* property name.
* @param Object lastToken
* The last token we added to the pretty printed results. If this is a
* getter or setter, it would be the `get` or `set` keyword
* respectively.
* @param Array stack
* The stack of open parens/curlies/brackets/etc.
*
* @returns Boolean
* True if this is a getter or setter.
*/
function isGetterOrSetter(token, lastToken, stack) {
return stack[stack.length - 1] == "{"
&& lastToken
&& lastToken.type.type == "name"
&& (lastToken.value == "get" || lastToken.value == "set")
&& token.type.type == "name";
}
/**
* Determine if we should add a newline after the given token.
*
* @param Object token
* The token we are looking at.
* @param Array stack
* The stack of open parens/curlies/brackets/etc.
*
* @returns Boolean
* True if we should add a newline.
*/
function isLineDelimiter(token, stack) {
if (token.isArrayLiteral) {
return true;
}
var ttt = token.type.type;
var top = stack[stack.length - 1];
return ttt == ";" && top != "("
|| ttt == "{"
|| ttt == "," && top != "("
|| ttt == ":" && (top == "case" || top == "default");
}
/**
* Append the necessary whitespace to the result after we have added the given
* token.
*
* @param Object token
* The token that was just added to the result.
* @param Function write
* The function to write to the pretty printed results.
* @param Array stack
* The stack of open parens/curlies/brackets/etc.
*
* @returns Boolean
* Returns true if we added a newline to result, false in all other
* cases.
*/
function appendNewline(token, write, stack) {
if (isLineDelimiter(token, stack)) {
write("\n", token.startLoc.line, token.startLoc.column);
return true;
}
return false;
}
/**
* Determines if we need to add a space between the last token we added and
* the token we are about to add.
*
* @param Object token
* The token we are about to add to the pretty printed code.
* @param Object lastToken
* The last token added to the pretty printed code.
*/
function needsSpaceAfter(token, lastToken) {
if (lastToken) {
if (lastToken.type.isLoop) {
return true;
}
if (lastToken.type.isAssign) {
return true;
}
if (lastToken.type.binop != null) {
return true;
}
var ltt = lastToken.type.type;
if (ltt == "?") {
return true;
}
if (ltt == ":") {
return true;
}
if (ltt == ",") {
return true;
}
if (ltt == ";") {
return true;
}
var ltk = lastToken.type.keyword;
if (ltk != null) {
if (ltk == "break" || ltk == "continue") {
return token.type.type != ";";
}
if (ltk != "debugger"
&& ltk != "null"
&& ltk != "true"
&& ltk != "false"
&& ltk != "this"
&& ltk != "default") {
return true;
}
}
if (ltt == ")" && (token.type.type != ")"
&& token.type.type != "]"
&& token.type.type != ";"
&& token.type.type != ",")) {
return true;
}
}
if (token.type.isAssign) {
return true;
}
if (token.type.binop != null) {
return true;
}
if (token.type.type == "?") {
return true;
}
return false;
}
/**
* Add the required whitespace before this token, whether that is a single
* space, newline, and/or the indent on fresh lines.
*
* @param Object token
* The token we are about to add to the pretty printed code.
* @param Object lastToken
* The last token we added to the pretty printed code.
* @param Boolean addedNewline
* Whether we added a newline after adding the last token to the pretty
* printed code.
* @param Function write
* The function to write pretty printed code to the result SourceNode.
* @param Object options
* The options object.
* @param Number indentLevel
* The number of indents deep we are.
* @param Array stack
* The stack of open curlies, brackets, etc.
*/
function prependWhiteSpace(token, lastToken, addedNewline, write, options,
indentLevel, stack) {
var ttk = token.type.keyword;
var ttt = token.type.type;
var newlineAdded = addedNewline;
var ltt = lastToken ? lastToken.type.type : null;
// Handle whitespace and newlines after "}" here instead of in
// `isLineDelimiter` because it is only a line delimiter some of the
// time. For example, we don't want to put "else if" on a new line after
// the first if's block.
if (lastToken && ltt == "}") {
if (ttk == "while" && stack[stack.length - 1] == "do") {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
} else if (ttk == "else" ||
ttk == "catch" ||
ttk == "finally") {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
} else if (ttt != "(" &&
ttt != ";" &&
ttt != "," &&
ttt != ")" &&
ttt != ".") {
write("\n",
lastToken.startLoc.line,
lastToken.startLoc.column);
newlineAdded = true;
}
}
if (isGetterOrSetter(token, lastToken, stack)) {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
}
if (ttt == ":" && stack[stack.length - 1] == "?") {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
}
if (lastToken && ltt != "}" && ttk == "else") {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
}
function ensureNewline() {
if (!newlineAdded) {
write("\n",
lastToken.startLoc.line,
lastToken.startLoc.column);
newlineAdded = true;
}
}
if (isASI(token, lastToken)) {
ensureNewline();
}
if (decrementsIndent(ttt, stack)) {
ensureNewline();
}
if (newlineAdded) {
if (ttk == "case" || ttk == "default") {
write(repeat(options.indent, indentLevel - 1),
token.startLoc.line,
token.startLoc.column);
} else {
write(repeat(options.indent, indentLevel),
token.startLoc.line,
token.startLoc.column);
}
} else if (needsSpaceAfter(token, lastToken)) {
write(" ",
lastToken.startLoc.line,
lastToken.startLoc.column);
}
}
/**
* Repeat the `str` string `n` times.
*
* @param String str
* The string to be repeated.
* @param Number n
* The number of times to repeat the string.
*
* @returns String
* The repeated string.
*/
function repeat(str, n) {
var result = "";
while (n > 0) {
if (n & 1) {
result += str;
}
n >>= 1;
str += str;
}
return result;
}
/**
* Make sure that we output the escaped character combination inside string literals
* instead of various problematic characters.
*/
var sanitize = (function () {
var escapeCharacters = {
// Backslash
"\\": "\\\\",
// Newlines
"\n": "\\n",
// Carriage return
"\r": "\\r",
// Tab
"\t": "\\t",
// Vertical tab
"\v": "\\v",
// Form feed
"\f": "\\f",
// Null character
"\0": "\\0",
// Single quotes
"'": "\\'"
};
var regExpString = "("
+ Object.keys(escapeCharacters)
.map(function (c) { return escapeCharacters[c]; })
.join("|")
+ ")";
var escapeCharactersRegExp = new RegExp(regExpString, "g");
return function(str) {
return str.replace(escapeCharactersRegExp, function (_, c) {
return escapeCharacters[c];
});
}
}());
/**
* Add the given token to the pretty printed results.
*
* @param Object token
* The token to add.
* @param Function write
* The function to write pretty printed code to the result SourceNode.
* @param Object options
* The options object.
*/
function addToken(token, write, options) {
if (token.type.type == "string") {
write("'" + sanitize(token.value) + "'",
token.startLoc.line,
token.startLoc.column);
} else {
write(String(token.value != null ? token.value : token.type.type),
token.startLoc.line,
token.startLoc.column);
}
}
/**
* Returns true if the given token type belongs on the stack.
*/
function belongsOnStack(token) {
var ttt = token.type.type;
var ttk = token.type.keyword;
return ttt == "{"
|| ttt == "("
|| ttt == "["
|| ttt == "?"
|| ttk == "do"
|| ttk == "case"
|| ttk == "default";
}
/**
* Returns true if the given token should cause us to pop the stack.
*/
function shouldStackPop(token, stack) {
var ttt = token.type.type;
var ttk = token.type.keyword;
var top = stack[stack.length - 1];
return ttt == "]"
|| ttt == ")"
|| ttt == "}"
|| (ttt == ":" && (top == "case" || top == "default" || top == "?"))
|| (ttk == "while" && top == "do");
}
/**
* Returns true if the given token type should cause us to decrement the
* indent level.
*/
function decrementsIndent(tokenType, stack) {
return tokenType == "}"
|| (tokenType == "]" && stack[stack.length - 1] == "[\n")
}
/**
* Returns true if the given token should cause us to increment the indent
* level.
*/
function incrementsIndent(token) {
return token.type.type == "{" || token.isArrayLiteral;
}
/**
* Add a comment to the pretty printed code.
*
* @param Function write
* The function to write pretty printed code to the result SourceNode.
* @param Number indentLevel
* The number of indents deep we are.
* @param Object options
* The options object.
* @param Boolean block
* True if the comment is a multiline block style comment.
* @param String text
* The text of the comment.
* @param Number line
* The line number to comment appeared on.
* @param Number column
* The column number the comment appeared on.
*/
function addComment(write, indentLevel, options, block, text, line, column) {
var indentString = repeat(options.indent, indentLevel);
write(indentString, line, column);
if (block) {
write("/*");
write(text
.split(new RegExp("/\n" + indentString + "/", "g"))
.join("\n" + indentString));
write("*/");
} else {
write("//");
write(text);
}
write("\n");
}
/**
* The main function.
*
* @param String input
* The ugly JS code we want to pretty print.
* @param Object options
* The options object. Provides configurability of the pretty
* printing. Properties:
* - url: The URL string of the ugly JS code.
* - indent: The string to indent code by.
*
* @returns Object
* An object with the following properties:
* - code: The pretty printed code string.
* - map: A SourceMapGenerator instance.
*/
return function prettyFast(input, options) {
// The level of indents deep we are.
var indentLevel = 0;
// We will accumulate the pretty printed code in this SourceNode.
var result = new SourceNode();
/**
* Write a pretty printed string to the result SourceNode.
*
* We buffer our writes so that we only create one mapping for each line in
* the source map. This enhances performance by avoiding extraneous mapping
* serialization, and flattening the tree that
* `SourceNode#toStringWithSourceMap` will have to recursively walk. When
* timing how long it takes to pretty print jQuery, this optimization
* brought the time down from ~390 ms to ~190ms!
*
* @param String str
* The string to be added to the result.
* @param Number line
* The line number the string came from in the ugly source.
* @param Number column
* The column number the string came from in the ugly source.
*/
var write = (function () {
var buffer = [];
var bufferLine = -1;
var bufferColumn = -1;
return function write(str, line, column) {
if (line != null && bufferLine === -1) {
bufferLine = line;
}
if (column != null && bufferColumn === -1) {
bufferColumn = column;
}
buffer.push(str);
if (str == "\n") {
var lineStr = "";
for (var i = 0, len = buffer.length; i < len; i++) {
lineStr += buffer[i];
}
result.add(new SourceNode(bufferLine, bufferColumn, options.url, lineStr));
buffer.splice(0, buffer.length);
bufferLine = -1;
bufferColumn = -1;
}
}
}());
// Whether or not we added a newline on after we added the last token.
var addedNewline = false;
// The current token we will be adding to the pretty printed code.
var token;
// Shorthand for token.type.type, so we don't have to repeatedly access
// properties.
var ttt;
// Shorthand for token.type.keyword, so we don't have to repeatedly access
// properties.
var ttk;
// The last token we added to the pretty printed code.
var lastToken;
// Stack of token types/keywords that can affect whether we want to add a
// newline or a space. We can make that decision based on what token type is
// on the top of the stack. For example, a comma in a parameter list should
// be followed by a space, while a comma in an object literal should be
// followed by a newline.
//
// Strings that go on the stack:
//
// - "{"
// - "("
// - "["
// - "[\n"
// - "do"
// - "?"
// - "case"
// - "default"
//
// The difference between "[" and "[\n" is that "[\n" is used when we are
// treating "[" and "]" tokens as line delimiters and should increment and
// decrement the indent level when we find them.
var stack = [];
// Acorn's tokenizer will always yield comments *before* the token they
// follow (unless the very first thing in the source is a comment), so we
// have to queue the comments in order to pretty print them in the correct
// location. For example, the source file:
//
// foo
// // a
// // b
// bar
//
// When tokenized by acorn, gives us the following token stream:
//
// [ '// a', '// b', foo, bar ]
var commentQueue = [];
var getToken = acorn.tokenize(input, {
locations: true,
sourceFile: options.url,
onComment: function (block, text, start, end, startLoc, endLoc) {
if (lastToken) {
commentQueue.push({
block: block,
text: text,
line: startLoc.line,
column: startLoc.column
});
} else {
addComment(write, indentLevel, options, block, text, startLoc.line,
startLoc.column);
addedNewline = true;
}
}
});
while (true) {
token = getToken();
ttk = token.type.keyword;
ttt = token.type.type;
if (ttt == "eof") {
if (!addedNewline) {
write("\n");
}
break;
}
token.isArrayLiteral = isArrayLiteral(token, lastToken);
if (belongsOnStack(token)) {
if (token.isArrayLiteral) {
stack.push("[\n");
} else {
stack.push(ttt || ttk);
}
}
if (decrementsIndent(ttt, stack)) {
indentLevel--;
}
prependWhiteSpace(token, lastToken, addedNewline, write, options,
indentLevel, stack);
addToken(token, write, options);
addedNewline = appendNewline(token, write, stack);
if (shouldStackPop(token, stack)) {
stack.pop();
}
if (incrementsIndent(token)) {
indentLevel++;
}
// Acorn's tokenizer re-uses tokens, so we have to copy the last token on
// every iteration. We follow acorn's lead here, and reuse the lastToken
// object the same way that acorn reuses the token object. This allows us
// to avoid allocations and minimize GC pauses.
if (!lastToken) {
lastToken = { startLoc: {}, endLoc: {} };
}
lastToken.start = token.start;
lastToken.end = token.end;
lastToken.startLoc.line = token.startLoc.line;
lastToken.startLoc.column = token.startLoc.column;
lastToken.endLoc.line = token.endLoc.line;
lastToken.endLoc.column = token.endLoc.column;
lastToken.type = token.type;
lastToken.value = token.value;
lastToken.isArrayLiteral = token.isArrayLiteral;
// Apply all the comments that have been queued up.
if (commentQueue.length) {
if (!addedNewline) {
write("\n");
}
for (var i = 0, n = commentQueue.length; i < n; i++) {
var comment = commentQueue[i];
addComment(write, indentLevel, options, comment.block, comment.text,
comment.line, comment.column);
}
addedNewline = true;
commentQueue.splice(0, commentQueue.length);
}
}
return result.toStringWithSourceMap({ file: options.url });
};
}.bind(this)));
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