1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433 | 1
1
1
1
1
875
551
504
77
77
77
1
133
1
77
26
1
384
1
55
55
13
13
55
6
55
55
55
4
1
295
244
244
1
299
299
299
299
299
299
299
299
1
299
299
295
295
77
35
35
10
10
10
10
10
10
10
10
10
10
10
1
67
67
67
67
67
2
32
13
10
1
299
299
299
299
299
19
19
19
19
299
431
43
47
47
2
47
299
1
10
10
10
133
133
10
123
2
2
121
3
3
118
3
3
123
10
1
10
10
133
133
133
1
132
10
1
10
10
10
7
10
1
35
35
35
348
10
37
14
14
14
14
7
10
338
4
35
1
1
1
1
1
1
1
1
1
1
10
10
6
4
1
6
6
6
6
6
6
6
3
6
4
4
2
4
3
4
1
4
3
3
1
2
| var traverse = require("../../traverse");
var util = require("../../util");
var t = require("../../types");
var _ = require("lodash");
var isLet = function (node) {
if (!t.isVariableDeclaration(node)) return false;
if (node._let) return true;
if (node.kind !== "let") return false;
node._let = true;
node.kind = "var";
return true;
};
var isVar = function (node) {
return t.isVariableDeclaration(node, { kind: "var" }) && !isLet(node);
};
var standardiseLets = function (declars) {
_.each(declars, function (declar) {
delete declar._let;
});
};
exports.VariableDeclaration = function (node) {
isLet(node);
};
exports.For = function (node, parent, file, scope) {
var init = node.left || node.init;
if (isLet(init)) {
t.ensureBlock(node);
node.body._letDeclars = [init];
}
if (t.isLabeledStatement(parent)) {
// set label so `run` has access to it
node.label = parent.label;
}
var letScoping = new LetScoping(node, node.body, parent, file, scope);
letScoping.run();
if (node.label && !t.isLabeledStatement(parent)) {
// we've been given a label so let's wrap ourselves
return t.labeledStatement(node.label, node);
}
};
exports.BlockStatement = function (block, parent, file, scope) {
if (!t.isFor(parent)) {
var letScoping = new LetScoping(false, block, parent, file, scope);
letScoping.run();
}
};
/**
* Description
*
* @param {Boolean|Node} forParent
* @param {Node} block
* @param {Node} parent
* @param {File} file
* @param {Scope} scope
*/
function LetScoping(forParent, block, parent, file, scope) {
this.forParent = forParent;
this.parent = parent;
this.scope = scope;
this.block = block;
this.file = file;
this.letReferences = {};
this.body = [];
this.info = this.getInfo();
}
/**
* Start the ball rolling.
*/
LetScoping.prototype.run = function () {
var block = this.block;
if (block._letDone) return;
block._letDone = true;
// this is a block within a `Function` so we can safely leave it be
if (t.isFunction(this.parent)) return;
// this block has no let references so let's clean up
if (!this.info.keys.length) return this.noClosure();
// returns whether or not there are any outside let references within any
// functions
var referencesInClosure = this.getLetReferences();
// no need for a closure so let's clean up
if (!referencesInClosure) return this.noClosure();
// if we're inside of a for loop then we search to see if there are any
// `break`s, `continue`s, `return`s etc
this.has = this.checkFor();
// hoist var references to retain scope
this.hoistVarDeclarations();
// set let references to plain var references
standardiseLets(this.info.declarators);
// turn letReferences into an array
var letReferences = _.values(this.letReferences);
// build the closure that we're going to wrap the block with
var fn = t.functionExpression(null, letReferences, t.blockStatement(block.body));
fn._aliasFunction = true;
// replace the current block body with the one we're going to build
block.body = this.body;
// change upper scope references with their uid if they have one
var params = this.getParams(letReferences);
// build a call and a unique id that we can assign the return value to
var call = t.callExpression(fn, params);
var ret = t.identifier(this.file.generateUid("ret", this.scope));
this.build(ret, call);
};
/**
* There are no let references accessed within a closure so we can just traverse
* through this block and replace all references that exist in a higher scope to
* their uids.
*/
LetScoping.prototype.noClosure = function () {
var replacements = this.info.duplicates;
var declarators = this.info.declarators;
var block = this.block;
standardiseLets(declarators);
if (_.isEmpty(replacements)) return;
traverse(block, function (node, parent) {
if (!t.isIdentifier(node)) return;
if (!t.isReferenced(node, parent)) return;
node.name = replacements[node.name] || node.name;
});
};
/**
* Description
*
* @returns {Object}
*/
LetScoping.prototype.getInfo = function () {
var block = this.block;
var scope = this.scope;
var file = this.file;
var opts = {
// array of `Identifier` names of let variables that appear lexically out of
// this scope but should be accessible - eg. `ForOfStatement`.left
outsideKeys: [],
// array of let `VariableDeclarator`s that are a part of this block
declarators: block._letDeclars || [],
// object of duplicate ids and their aliases - if there's an `Identifier`
// name that's used in an upper scope we generate a unique id and replace
// all references with it
duplicates: {},
// array of `Identifier` names of let variables that are accessible within
// the current block
keys: []
};
_.each(opts.declarators, function (declar) {
opts.declarators.push(declar);
var keys = t.getIds(declar);
opts.outsideKeys = opts.outsideKeys.concat(keys);
opts.keys = opts.keys.concat(keys);
});
_.each(block.body, function (declar) {
if (!isLet(declar)) return;
_.each(t.getIds(declar, true), function (id, key) {
var has = scope.parentGet(key);
if (has && has !== id) {
// there's a variable with this exact name in an upper scope so we need
// to generate a new name
opts.duplicates[key] = id.name = file.generateUid(key, scope);
}
opts.keys.push(key);
});
});
return opts;
};
/**
* If we're inside of a `For*Statement` then traverse it and check if it has one
* of the following node types `ReturnStatement`, `BreakStatement`,
* `ContinueStatement` and replace it with a return value that we can track
* later on.
*
* @returns {Object}
*/
LetScoping.prototype.checkFor = function () {
var has = {
hasContinue: false,
hasReturn: false,
hasBreak: false,
};
Eif (this.forParent) {
traverse(this.block, function (node) {
var replace;
if (t.isFunction(node) || t.isFor(node)) {
return false;
} else if (t.isBreakStatement(node) && !node.label) {
has.hasBreak = true;
replace = t.returnStatement(t.literal("break"));
} else if (t.isContinueStatement(node) && !node.label) {
has.hasContinue = true;
replace = t.returnStatement(t.literal("continue"));
} else if (t.isReturnStatement(node)) {
has.hasReturn = true;
replace = t.returnStatement(t.objectExpression([
t.property("init", t.identifier("v"), node.argument || t.identifier("undefined"))
]));
}
if (replace) return t.inherits(replace, node);
});
}
return has;
};
/**
* Hoist all var declarations in this block to before it so they retain scope
* once we wrap everything in a closure.
*/
LetScoping.prototype.hoistVarDeclarations = function () {
var self = this;
traverse(this.block, function (node) {
Iif (t.isForStatement(node)) {
if (isVar(node.init)) {
node.init = t.sequenceExpression(self.pushDeclar(node.init));
}
} else Iif (t.isFor(node)) {
if (isVar(node.left)) {
node.left = node.left.declarations[0].id;
}
} else if (isVar(node)) {
return self.pushDeclar(node).map(t.expressionStatement);
} else if (t.isFunction(node)) {
return false;
}
});
};
/**
* Build up a parameter list that we'll call our closure wrapper with, replacing
* all duplicate ids with their uid.
*
* @param {Array} params
* @returns {Array}
*/
LetScoping.prototype.getParams = function (params) {
var info = this.info;
params = _.cloneDeep(params);
_.each(params, function (param) {
param.name = info.duplicates[param.name] || param.name;
});
return params;
};
/**
* Get all let references within this block. Stopping whenever we reach another
* block.
*/
LetScoping.prototype.getLetReferences = function () {
var closurify = false;
var self = this;
// traverse through this block, stopping on functions and checking if they
// contain any outside let references
traverse(this.block, function (node, parent, scope) {
if (t.isFunction(node)) {
traverse(node, function (node, parent) {
// not an identifier so we have no use
if (!t.isIdentifier(node)) return;
// not a direct reference
Iif (!t.isReferenced(node, parent)) return;
// this scope has a variable with the same name so it couldn't belong
// to our let scope
Iif (scope.hasOwn(node.name)) return;
closurify = true;
// this key doesn't appear just outside our scope
if (!_.contains(self.info.outsideKeys, node.name)) return;
// push this badboy
self.letReferences[node.name] = node;
});
return false;
} else if (t.isFor(node)) {
return false;
}
});
return closurify;
};
/**
* Turn a `VariableDeclaration` into an array of `AssignmentExpressions` with
* their declarations hoisted to before the closure wrapper.
*
* @param {Node} node VariableDeclaration
* @returns {Array}
*/
LetScoping.prototype.pushDeclar = function (node) {
this.body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
return t.variableDeclarator(declar.id);
})));
var replace = [];
_.each(node.declarations, function (declar) {
Iif (!declar.init) return;
var expr = t.assignmentExpression("=", declar.id, declar.init);
replace.push(t.inherits(expr, declar));
});
return replace;
};
/**
* Push the closure to the body.
*
* @param {Node} ret Identifier
* @param {Node} call CallExpression
*/
LetScoping.prototype.build = function (ret, call) {
var has = this.has;
if (has.hasReturn || has.hasBreak || has.hasContinue) {
this.buildHas(ret, call);
} else {
this.body.push(t.expressionStatement(call));
}
};
/**
* Description
*
* @param {Node} ret Identifier
* @param {Node} call CallExpression
*/
LetScoping.prototype.buildHas = function (ret, call) {
var body = this.body;
body.push(t.variableDeclaration("var", [
t.variableDeclarator(ret, call)
]));
var forParent = this.forParent;
var retCheck;
var has = this.has;
var cases = [];
if (has.hasReturn) {
// typeof ret === "object"
retCheck = util.template("let-scoping-return", {
RETURN: ret
});
}
if (has.hasBreak || has.hasContinue) {
// ensure that the parent has a label as we're building a switch and we
// need to be able to access it
var label = forParent.label = forParent.label || t.identifier(this.file.generateUid("loop", this.scope));
if (has.hasBreak) {
cases.push(t.switchCase(t.literal("break"), [t.breakStatement(label)]));
}
if (has.hasContinue) {
cases.push(t.switchCase(t.literal("continue"), [t.continueStatement(label)]));
}
if (has.hasReturn) {
cases.push(t.switchCase(null, [retCheck]));
}
if (cases.length === 1) {
var single = cases[0];
body.push(t.ifStatement(
t.binaryExpression("===", ret, single.test),
single.consequent[0]
));
} else {
body.push(t.switchStatement(ret, cases));
}
} else {
Eif (has.hasReturn) body.push(retCheck);
}
};
|