gnome-shell/js/misc/jsParse.js

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/* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
/* exported getCompletions, getCommonPrefix, getDeclaredConstants */
// Returns a list of potential completions for text. Completions either
// follow a dot (e.g. foo.ba -> bar) or they are picked from globalCompletionList (e.g. fo -> foo)
// commandHeader is prefixed on any expression before it is eval'ed. It will most likely
// consist of global constants that might not carry over from the calling environment.
//
// This function is likely the one you want to call from external modules
function getCompletions(text, commandHeader, globalCompletionList) {
let methods = [];
let expr_, base;
let attrHead = '';
if (globalCompletionList == null) {
globalCompletionList = [];
}
let offset = getExpressionOffset(text, text.length - 1);
if (offset >= 0) {
text = text.slice(offset);
// Look for expressions like "Main.panel.foo" and match Main.panel and foo
let matches = text.match(/(.*)\.(.*)/);
if (matches) {
[expr_, base, attrHead] = matches;
methods = getPropertyNamesFromExpression(base, commandHeader).filter(
attr => attr.slice(0, attrHead.length) == attrHead
);
}
// Look for the empty expression or partially entered words
// not proceeded by a dot and match them against global constants
matches = text.match(/^(\w*)$/);
if (text == '' || matches) {
[expr_, attrHead] = matches;
methods = globalCompletionList.filter(
attr => attr.slice(0, attrHead.length) == attrHead
);
}
}
return [methods, attrHead];
}
//
// A few functions for parsing strings of javascript code.
//
// Identify characters that delimit an expression. That is,
// if we encounter anything that isn't a letter, '.', ')', or ']',
// we should stop parsing.
function isStopChar(c) {
return !c.match(/[\w.)\]]/);
}
// Given the ending position of a quoted string, find where it starts
function findMatchingQuote(expr, offset) {
let quoteChar = expr.charAt(offset);
for (let i = offset - 1; i >= 0; --i) {
if (expr.charAt(i) == quoteChar && expr.charAt(i - 1) != '\\') {
return i;
}
}
return -1;
}
// Given the ending position of a regex, find where it starts
function findMatchingSlash(expr, offset) {
for (let i = offset - 1; i >= 0; --i) {
if (expr.charAt(i) == '/' && expr.charAt(i - 1) != '\\') {
return i;
}
}
return -1;
}
// If expr.charAt(offset) is ')' or ']',
// return the position of the corresponding '(' or '[' bracket.
// This function does not check for syntactic correctness. e.g.,
// findMatchingBrace("[(])", 3) returns 1.
function findMatchingBrace(expr, offset) {
let closeBrace = expr.charAt(offset);
let openBrace = ({ ')': '(', ']': '[' })[closeBrace];
function findTheBrace(expr, offset) {
if (offset < 0) {
return -1;
}
if (expr.charAt(offset) == openBrace) {
return offset;
}
if (expr.charAt(offset).match(/['"]/)) {
return findTheBrace(expr, findMatchingQuote(expr, offset) - 1);
}
if (expr.charAt(offset) == '/') {
return findTheBrace(expr, findMatchingSlash(expr, offset) - 1);
}
if (expr.charAt(offset) == closeBrace) {
return findTheBrace(expr, findTheBrace(expr, offset - 1) - 1);
}
return findTheBrace(expr, offset - 1);
}
return findTheBrace(expr, offset - 1);
}
// Walk expr backwards from offset looking for the beginning of an
// expression suitable for passing to eval.
// There is no guarantee of correct javascript syntax between the return
// value and offset. This function is meant to take a string like
// "foo(Obj.We.Are.Completing" and allow you to extract "Obj.We.Are.Completing"
function getExpressionOffset(expr, offset) {
while (offset >= 0) {
let currChar = expr.charAt(offset);
if (isStopChar(currChar)) {
return offset + 1;
}
if (currChar.match(/[)\]]/)) {
offset = findMatchingBrace(expr, offset);
}
--offset;
}
return offset + 1;
}
// Things with non-word characters or that start with a number
// are not accessible via .foo notation and so aren't returned
function isValidPropertyName(w) {
return !(w.match(/\W/) || w.match(/^\d/));
}
// To get all properties (enumerable and not), we need to walk
// the prototype chain ourselves
function getAllProps(obj) {
if (obj === null || obj === undefined) {
return [];
}
return Object.getOwnPropertyNames(obj).concat( getAllProps(Object.getPrototypeOf(obj)) );
}
// Given a string _expr_, returns all methods
// that can be accessed via '.' notation.
// e.g., expr="({ foo: null, bar: null, 4: null })" will
// return ["foo", "bar", ...] but the list will not include "4",
// since methods accessed with '.' notation must star with a letter or _.
function getPropertyNamesFromExpression(expr, commandHeader = '') {
let obj = {};
if (!isUnsafeExpression(expr)) {
try {
obj = eval(commandHeader + expr);
} catch (e) {
return [];
}
} else {
return [];
}
let propsUnique = {};
if (typeof obj === 'object') {
let allProps = getAllProps(obj);
// Get only things we are allowed to complete following a '.'
allProps = allProps.filter( isValidPropertyName );
// Make sure propsUnique contains one key for every
// property so we end up with a unique list of properties
allProps.map(p => (propsUnique[p] = null));
}
return Object.keys(propsUnique).sort();
}
// Given a list of words, returns the longest prefix they all have in common
function getCommonPrefix(words) {
let word = words[0];
for (let i = 0; i < word.length; i++) {
for (let w = 1; w < words.length; w++) {
if (words[w].charAt(i) != word.charAt(i))
return word.slice(0, i);
}
}
return word;
}
// Returns true if there is reason to think that eval(str)
// will modify the global scope
function isUnsafeExpression(str) {
// Remove any blocks that are quoted or are in a regex
function removeLiterals(str) {
if (str.length == 0) {
return '';
}
let currChar = str.charAt(str.length - 1);
if (currChar == '"' || currChar == '\'') {
return removeLiterals(str.slice(0, findMatchingQuote(str, str.length - 1)));
} else if (currChar == '/') {
return removeLiterals(str.slice(0, findMatchingSlash(str, str.length - 1)));
}
return removeLiterals(str.slice(0, str.length - 1)) + currChar;
}
// Check for any sort of assignment
// The strategy used is dumb: remove any quotes
// or regexs and comparison operators and see if there is an '=' character.
// If there is, it might be an unsafe assignment.
let prunedStr = removeLiterals(str);
prunedStr = prunedStr.replace(/[=!]==/g, ''); //replace === and !== with nothing
prunedStr = prunedStr.replace(/[=<>!]=/g, ''); //replace ==, <=, >=, != with nothing
if (prunedStr.match(/[=]/)) {
return true;
} else if (prunedStr.match(/;/)) {
// If we contain a semicolon not inside of a quote/regex, assume we're unsafe as well
return true;
}
return false;
}
// Returns a list of global keywords derived from str
function getDeclaredConstants(str) {
let ret = [];
str.split(';').forEach(s => {
let base_, keyword;
let match = s.match(/const\s+(\w+)\s*=/);
if (match) {
[base_, keyword] = match;
ret.push(keyword);
}
});
return ret;
}