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3
| var traverse = require("../../traverse");
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);
};
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;
}
run(node, node.body, parent, file, scope);
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)) {
run(false, block, parent, file, scope);
}
};
var noClosure = function (letDeclars, block, replacements) {
standardiseLets(letDeclars);
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;
});
};
var standardiseLets = function (declars) {
_.each(declars, function (declar) {
delete declar._let;
});
};
var getInfo = function (block, file, scope) {
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;
};
var checkFor = function (forParent, block) {
var has = {
hasContinue: false,
hasReturn: false,
hasBreak: false,
};
Eif (forParent) {
traverse(block, function (node) {
var replace;
if (t.isFunction(node) || t.isFor(node)) {
return false;
} else Iif (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 Iif (t.isReturnStatement(node)) {
has.hasReturn = true;
replace = t.returnStatement(t.objectExpression([
t.property("init", t.identifier("v"), node.argument)
]));
}
if (replace) return t.inherits(replace, node);
});
}
return has;
};
var hoistVarDeclarations = function (block, pushDeclar) {
traverse(block, function (node) {
Iif (t.isForStatement(node)) {
if (isVar(node.init)) {
node.init = t.sequenceExpression(pushDeclar(node.init));
}
} else Iif (t.isFor(node)) {
if (isVar(node.left)) {
node.left = node.left.declarations[0].id;
}
} else Iif (isVar(node)) {
return pushDeclar(node).map(t.expressionStatement);
} else if (t.isFunction(node)) {
return false;
}
});
};
var getLetReferences = function (info, block, letReferences) {
var closurify = false;
// traverse through this block, stopping on functions and checking if they
// contain any outside let references
traverse(block, function (node, parent, opts) {
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 (opts.scope.hasOwn(node.name)) return;
closurify = true;
// this key doesn't appear just outside our scope
if (!_.contains(info.outsideKeys, node.name)) return;
// push this badboy
letReferences[node.name] = node;
});
return false;
} else if (t.isFor(node)) {
return false;
}
});
return closurify;
};
var run = function (forParent, block, parent, file, scope) {
if (block._letDone) return;
block._letDone = true;
var info = getInfo(block, file, scope);
var declarators = info.declarators;
var letKeys = info.keys;
// this is a block within a `Function` so we can safely leave it be
if (t.isFunction(parent)) return;
// this block has no let references so let's clean up
if (!letKeys.length) return noClosure(declarators, block, info.duplicates);
// outside let references that we need to wrap
var letReferences = {};
// returns whether or not there are any outside let references within any
// functions
var closurify = getLetReferences(info, block, letReferences);
letReferences = _.values(letReferences);
// no need for a closure so let's clean up
if (!closurify) return noClosure(declarators, block, info.duplicates);
// if we're inside of a for loop then we search to see if there are any
// `break`s, `continue`s, `return`s etc
var has = checkFor(forParent, block);
var body = [];
// hoist a `VariableDeclaration` and add `AssignmentExpression`s in it's place
var pushDeclar = function (node) {
body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
return t.variableDeclarator(declar.id);
})));
var replace = [];
_.each(node.declarations, function (declar) {
if (!declar.init) return;
var expr = t.assignmentExpression("=", declar.id, declar.init);
replace.push(t.inherits(expr, declar));
});
return replace;
};
// hoist var references to retain scope
hoistVarDeclarations(block, pushDeclar);
// set let references to plain var references
standardiseLets(declarators);
// 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've built
block.body = body;
// cahnge duplicate let references to their uid if they have one
var params = _.cloneDeep(letReferences);
_.each(params, function (param) {
param.name = info.duplicates[param.name] || param.name;
});
var call = t.callExpression(fn, params);
var ret = t.identifier(file.generateUid("ret", scope));
if (has.hasReturn || has.hasBreak || has.hasContinue) {
body.push(t.variableDeclaration("var", [
t.variableDeclarator(ret, call)
]));
var retCheck;
Iif (has.hasReturn) {
// typeof ret === "object"
retCheck = t.ifStatement(
t.binaryExpression("===", t.unaryExpression("typeof", ret, true), t.literal("object")),
t.returnStatement(t.memberExpression(ret, t.identifier("v")))
);
// there's no `break` or `continue` so we can just push in the `if`
if (!has.hasBreak && !has.hasContinue) {
body.push(retCheck);
}
}
Eif (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(file.generateUid("loop", scope));
var cases = [];
Iif (has.hasBreak) {
cases.push(t.switchCase(t.literal("break"), [t.breakStatement(label)]));
}
Eif (has.hasContinue) {
cases.push(t.switchCase(t.literal("continue"), [t.continueStatement(label)]));
}
Iif (has.hasReturn) {
cases.push(t.switchCase(null, [retCheck]));
}
body.push(t.switchStatement(ret, cases));
}
} else {
body.push(t.expressionStatement(call));
}
};
|