/**
|
* Copyright (c) 2014-present, Facebook, Inc.
|
*
|
* This source code is licensed under the MIT license found in the
|
* LICENSE file in the root directory of this source tree.
|
*/
|
|
import assert from "assert";
|
import * as leap from "./leap";
|
import * as meta from "./meta";
|
import * as util from "./util";
|
|
let hasOwn = Object.prototype.hasOwnProperty;
|
|
function Emitter(contextId) {
|
assert.ok(this instanceof Emitter);
|
|
util.getTypes().assertIdentifier(contextId);
|
|
// Used to generate unique temporary names.
|
this.nextTempId = 0;
|
|
// In order to make sure the context object does not collide with
|
// anything in the local scope, we might have to rename it, so we
|
// refer to it symbolically instead of just assuming that it will be
|
// called "context".
|
this.contextId = contextId;
|
|
// An append-only list of Statements that grows each time this.emit is
|
// called.
|
this.listing = [];
|
|
// A sparse array whose keys correspond to locations in this.listing
|
// that have been marked as branch/jump targets.
|
this.marked = [true];
|
|
this.insertedLocs = new Set();
|
|
// The last location will be marked when this.getDispatchLoop is
|
// called.
|
this.finalLoc = this.loc();
|
|
// A list of all leap.TryEntry statements emitted.
|
this.tryEntries = [];
|
|
// Each time we evaluate the body of a loop, we tell this.leapManager
|
// to enter a nested loop context that determines the meaning of break
|
// and continue statements therein.
|
this.leapManager = new leap.LeapManager(this);
|
}
|
|
let Ep = Emitter.prototype;
|
exports.Emitter = Emitter;
|
|
// Offsets into this.listing that could be used as targets for branches or
|
// jumps are represented as numeric Literal nodes. This representation has
|
// the amazingly convenient benefit of allowing the exact value of the
|
// location to be determined at any time, even after generating code that
|
// refers to the location.
|
Ep.loc = function() {
|
const l = util.getTypes().numericLiteral(-1)
|
this.insertedLocs.add(l);
|
return l;
|
}
|
|
Ep.getInsertedLocs = function() {
|
return this.insertedLocs;
|
}
|
|
Ep.getContextId = function() {
|
return util.getTypes().clone(this.contextId);
|
}
|
|
// Sets the exact value of the given location to the offset of the next
|
// Statement emitted.
|
Ep.mark = function(loc) {
|
util.getTypes().assertLiteral(loc);
|
let index = this.listing.length;
|
if (loc.value === -1) {
|
loc.value = index;
|
} else {
|
// Locations can be marked redundantly, but their values cannot change
|
// once set the first time.
|
assert.strictEqual(loc.value, index);
|
}
|
this.marked[index] = true;
|
return loc;
|
};
|
|
Ep.emit = function(node) {
|
const t = util.getTypes();
|
|
if (t.isExpression(node)) {
|
node = t.expressionStatement(node);
|
}
|
|
t.assertStatement(node);
|
this.listing.push(node);
|
};
|
|
// Shorthand for emitting assignment statements. This will come in handy
|
// for assignments to temporary variables.
|
Ep.emitAssign = function(lhs, rhs) {
|
this.emit(this.assign(lhs, rhs));
|
return lhs;
|
};
|
|
// Shorthand for an assignment statement.
|
Ep.assign = function(lhs, rhs) {
|
const t = util.getTypes();
|
return t.expressionStatement(
|
t.assignmentExpression("=", t.cloneDeep(lhs), rhs));
|
};
|
|
// Convenience function for generating expressions like context.next,
|
// context.sent, and context.rval.
|
Ep.contextProperty = function(name, computed) {
|
const t = util.getTypes();
|
return t.memberExpression(
|
this.getContextId(),
|
computed ? t.stringLiteral(name) : t.identifier(name),
|
!!computed
|
);
|
};
|
|
// Shorthand for setting context.rval and jumping to `context.stop()`.
|
Ep.stop = function(rval) {
|
if (rval) {
|
this.setReturnValue(rval);
|
}
|
|
this.jump(this.finalLoc);
|
};
|
|
Ep.setReturnValue = function(valuePath) {
|
util.getTypes().assertExpression(valuePath.value);
|
|
this.emitAssign(
|
this.contextProperty("rval"),
|
this.explodeExpression(valuePath)
|
);
|
};
|
|
Ep.clearPendingException = function(tryLoc, assignee) {
|
const t = util.getTypes();
|
|
t.assertLiteral(tryLoc);
|
|
let catchCall = t.callExpression(
|
this.contextProperty("catch", true),
|
[t.clone(tryLoc)]
|
);
|
|
if (assignee) {
|
this.emitAssign(assignee, catchCall);
|
} else {
|
this.emit(catchCall);
|
}
|
};
|
|
// Emits code for an unconditional jump to the given location, even if the
|
// exact value of the location is not yet known.
|
Ep.jump = function(toLoc) {
|
this.emitAssign(this.contextProperty("next"), toLoc);
|
this.emit(util.getTypes().breakStatement());
|
};
|
|
// Conditional jump.
|
Ep.jumpIf = function(test, toLoc) {
|
const t = util.getTypes();
|
|
t.assertExpression(test);
|
t.assertLiteral(toLoc);
|
|
this.emit(t.ifStatement(
|
test,
|
t.blockStatement([
|
this.assign(this.contextProperty("next"), toLoc),
|
t.breakStatement()
|
])
|
));
|
};
|
|
// Conditional jump, with the condition negated.
|
Ep.jumpIfNot = function(test, toLoc) {
|
const t = util.getTypes();
|
|
t.assertExpression(test);
|
t.assertLiteral(toLoc);
|
|
let negatedTest;
|
if (t.isUnaryExpression(test) &&
|
test.operator === "!") {
|
// Avoid double negation.
|
negatedTest = test.argument;
|
} else {
|
negatedTest = t.unaryExpression("!", test);
|
}
|
|
this.emit(t.ifStatement(
|
negatedTest,
|
t.blockStatement([
|
this.assign(this.contextProperty("next"), toLoc),
|
t.breakStatement()
|
])
|
));
|
};
|
|
// Returns a unique MemberExpression that can be used to store and
|
// retrieve temporary values. Since the object of the member expression is
|
// the context object, which is presumed to coexist peacefully with all
|
// other local variables, and since we just increment `nextTempId`
|
// monotonically, uniqueness is assured.
|
Ep.makeTempVar = function() {
|
return this.contextProperty("t" + this.nextTempId++);
|
};
|
|
Ep.getContextFunction = function(id) {
|
const t = util.getTypes();
|
|
return t.functionExpression(
|
id || null/*Anonymous*/,
|
[this.getContextId()],
|
t.blockStatement([this.getDispatchLoop()]),
|
false, // Not a generator anymore!
|
false // Nor an expression.
|
);
|
};
|
|
// Turns this.listing into a loop of the form
|
//
|
// while (1) switch (context.next) {
|
// case 0:
|
// ...
|
// case n:
|
// return context.stop();
|
// }
|
//
|
// Each marked location in this.listing will correspond to one generated
|
// case statement.
|
Ep.getDispatchLoop = function() {
|
const self = this;
|
const t = util.getTypes();
|
let cases = [];
|
let current;
|
|
// If we encounter a break, continue, or return statement in a switch
|
// case, we can skip the rest of the statements until the next case.
|
let alreadyEnded = false;
|
|
self.listing.forEach(function(stmt, i) {
|
if (self.marked.hasOwnProperty(i)) {
|
cases.push(t.switchCase(
|
t.numericLiteral(i),
|
current = []));
|
alreadyEnded = false;
|
}
|
|
if (!alreadyEnded) {
|
current.push(stmt);
|
if (t.isCompletionStatement(stmt))
|
alreadyEnded = true;
|
}
|
});
|
|
// Now that we know how many statements there will be in this.listing,
|
// we can finally resolve this.finalLoc.value.
|
this.finalLoc.value = this.listing.length;
|
|
cases.push(
|
t.switchCase(this.finalLoc, [
|
// Intentionally fall through to the "end" case...
|
]),
|
|
// So that the runtime can jump to the final location without having
|
// to know its offset, we provide the "end" case as a synonym.
|
t.switchCase(t.stringLiteral("end"), [
|
// This will check/clear both context.thrown and context.rval.
|
t.returnStatement(
|
t.callExpression(this.contextProperty("stop"), [])
|
)
|
])
|
);
|
|
return t.whileStatement(
|
t.numericLiteral(1),
|
t.switchStatement(
|
t.assignmentExpression(
|
"=",
|
this.contextProperty("prev"),
|
this.contextProperty("next")
|
),
|
cases
|
)
|
);
|
};
|
|
Ep.getTryLocsList = function() {
|
if (this.tryEntries.length === 0) {
|
// To avoid adding a needless [] to the majority of runtime.wrap
|
// argument lists, force the caller to handle this case specially.
|
return null;
|
}
|
|
const t = util.getTypes();
|
let lastLocValue = 0;
|
|
return t.arrayExpression(
|
this.tryEntries.map(function(tryEntry) {
|
let thisLocValue = tryEntry.firstLoc.value;
|
assert.ok(thisLocValue >= lastLocValue, "try entries out of order");
|
lastLocValue = thisLocValue;
|
|
let ce = tryEntry.catchEntry;
|
let fe = tryEntry.finallyEntry;
|
|
let locs = [
|
tryEntry.firstLoc,
|
// The null here makes a hole in the array.
|
ce ? ce.firstLoc : null
|
];
|
|
if (fe) {
|
locs[2] = fe.firstLoc;
|
locs[3] = fe.afterLoc;
|
}
|
|
return t.arrayExpression(locs.map(loc => loc && t.clone(loc)));
|
})
|
);
|
};
|
|
// All side effects must be realized in order.
|
|
// If any subexpression harbors a leap, all subexpressions must be
|
// neutered of side effects.
|
|
// No destructive modification of AST nodes.
|
|
Ep.explode = function(path, ignoreResult) {
|
const t = util.getTypes();
|
let node = path.node;
|
let self = this;
|
|
t.assertNode(node);
|
|
if (t.isDeclaration(node))
|
throw getDeclError(node);
|
|
if (t.isStatement(node))
|
return self.explodeStatement(path);
|
|
if (t.isExpression(node))
|
return self.explodeExpression(path, ignoreResult);
|
|
switch (node.type) {
|
case "Program":
|
return path.get("body").map(
|
self.explodeStatement,
|
self
|
);
|
|
case "VariableDeclarator":
|
throw getDeclError(node);
|
|
// These node types should be handled by their parent nodes
|
// (ObjectExpression, SwitchStatement, and TryStatement, respectively).
|
case "Property":
|
case "SwitchCase":
|
case "CatchClause":
|
throw new Error(
|
node.type + " nodes should be handled by their parents");
|
|
default:
|
throw new Error(
|
"unknown Node of type " +
|
JSON.stringify(node.type));
|
}
|
};
|
|
function getDeclError(node) {
|
return new Error(
|
"all declarations should have been transformed into " +
|
"assignments before the Exploder began its work: " +
|
JSON.stringify(node));
|
}
|
|
Ep.explodeStatement = function(path, labelId) {
|
const t = util.getTypes();
|
let stmt = path.node;
|
let self = this;
|
let before, after, head;
|
|
t.assertStatement(stmt);
|
|
if (labelId) {
|
t.assertIdentifier(labelId);
|
} else {
|
labelId = null;
|
}
|
|
// Explode BlockStatement nodes even if they do not contain a yield,
|
// because we don't want or need the curly braces.
|
if (t.isBlockStatement(stmt)) {
|
path.get("body").forEach(function (path) {
|
self.explodeStatement(path);
|
});
|
return;
|
}
|
|
if (!meta.containsLeap(stmt)) {
|
// Technically we should be able to avoid emitting the statement
|
// altogether if !meta.hasSideEffects(stmt), but that leads to
|
// confusing generated code (for instance, `while (true) {}` just
|
// disappears) and is probably a more appropriate job for a dedicated
|
// dead code elimination pass.
|
self.emit(stmt);
|
return;
|
}
|
|
switch (stmt.type) {
|
case "ExpressionStatement":
|
self.explodeExpression(path.get("expression"), true);
|
break;
|
|
case "LabeledStatement":
|
after = this.loc();
|
|
// Did you know you can break from any labeled block statement or
|
// control structure? Well, you can! Note: when a labeled loop is
|
// encountered, the leap.LabeledEntry created here will immediately
|
// enclose a leap.LoopEntry on the leap manager's stack, and both
|
// entries will have the same label. Though this works just fine, it
|
// may seem a bit redundant. In theory, we could check here to
|
// determine if stmt knows how to handle its own label; for example,
|
// stmt happens to be a WhileStatement and so we know it's going to
|
// establish its own LoopEntry when we explode it (below). Then this
|
// LabeledEntry would be unnecessary. Alternatively, we might be
|
// tempted not to pass stmt.label down into self.explodeStatement,
|
// because we've handled the label here, but that's a mistake because
|
// labeled loops may contain labeled continue statements, which is not
|
// something we can handle in this generic case. All in all, I think a
|
// little redundancy greatly simplifies the logic of this case, since
|
// it's clear that we handle all possible LabeledStatements correctly
|
// here, regardless of whether they interact with the leap manager
|
// themselves. Also remember that labels and break/continue-to-label
|
// statements are rare, and all of this logic happens at transform
|
// time, so it has no additional runtime cost.
|
self.leapManager.withEntry(
|
new leap.LabeledEntry(after, stmt.label),
|
function() {
|
self.explodeStatement(path.get("body"), stmt.label);
|
}
|
);
|
|
self.mark(after);
|
|
break;
|
|
case "WhileStatement":
|
before = this.loc();
|
after = this.loc();
|
|
self.mark(before);
|
self.jumpIfNot(self.explodeExpression(path.get("test")), after);
|
self.leapManager.withEntry(
|
new leap.LoopEntry(after, before, labelId),
|
function() { self.explodeStatement(path.get("body")); }
|
);
|
self.jump(before);
|
self.mark(after);
|
|
break;
|
|
case "DoWhileStatement":
|
let first = this.loc();
|
let test = this.loc();
|
after = this.loc();
|
|
self.mark(first);
|
self.leapManager.withEntry(
|
new leap.LoopEntry(after, test, labelId),
|
function() { self.explode(path.get("body")); }
|
);
|
self.mark(test);
|
self.jumpIf(self.explodeExpression(path.get("test")), first);
|
self.mark(after);
|
|
break;
|
|
case "ForStatement":
|
head = this.loc();
|
let update = this.loc();
|
after = this.loc();
|
|
if (stmt.init) {
|
// We pass true here to indicate that if stmt.init is an expression
|
// then we do not care about its result.
|
self.explode(path.get("init"), true);
|
}
|
|
self.mark(head);
|
|
if (stmt.test) {
|
self.jumpIfNot(self.explodeExpression(path.get("test")), after);
|
} else {
|
// No test means continue unconditionally.
|
}
|
|
self.leapManager.withEntry(
|
new leap.LoopEntry(after, update, labelId),
|
function() { self.explodeStatement(path.get("body")); }
|
);
|
|
self.mark(update);
|
|
if (stmt.update) {
|
// We pass true here to indicate that if stmt.update is an
|
// expression then we do not care about its result.
|
self.explode(path.get("update"), true);
|
}
|
|
self.jump(head);
|
|
self.mark(after);
|
|
break;
|
|
case "TypeCastExpression":
|
return self.explodeExpression(path.get("expression"));
|
|
case "ForInStatement":
|
head = this.loc();
|
after = this.loc();
|
|
let keyIterNextFn = self.makeTempVar();
|
self.emitAssign(
|
keyIterNextFn,
|
t.callExpression(
|
util.runtimeProperty("keys"),
|
[self.explodeExpression(path.get("right"))]
|
)
|
);
|
|
self.mark(head);
|
|
let keyInfoTmpVar = self.makeTempVar();
|
self.jumpIf(
|
t.memberExpression(
|
t.assignmentExpression(
|
"=",
|
keyInfoTmpVar,
|
t.callExpression(t.cloneDeep(keyIterNextFn), [])
|
),
|
t.identifier("done"),
|
false
|
),
|
after
|
);
|
|
self.emitAssign(
|
stmt.left,
|
t.memberExpression(
|
t.cloneDeep(keyInfoTmpVar),
|
t.identifier("value"),
|
false
|
)
|
);
|
|
self.leapManager.withEntry(
|
new leap.LoopEntry(after, head, labelId),
|
function() { self.explodeStatement(path.get("body")); }
|
);
|
|
self.jump(head);
|
|
self.mark(after);
|
|
break;
|
|
case "BreakStatement":
|
self.emitAbruptCompletion({
|
type: "break",
|
target: self.leapManager.getBreakLoc(stmt.label)
|
});
|
|
break;
|
|
case "ContinueStatement":
|
self.emitAbruptCompletion({
|
type: "continue",
|
target: self.leapManager.getContinueLoc(stmt.label)
|
});
|
|
break;
|
|
case "SwitchStatement":
|
// Always save the discriminant into a temporary variable in case the
|
// test expressions overwrite values like context.sent.
|
let disc = self.emitAssign(
|
self.makeTempVar(),
|
self.explodeExpression(path.get("discriminant"))
|
);
|
|
after = this.loc();
|
let defaultLoc = this.loc();
|
let condition = defaultLoc;
|
let caseLocs = [];
|
|
// If there are no cases, .cases might be undefined.
|
let cases = stmt.cases || [];
|
|
for (let i = cases.length - 1; i >= 0; --i) {
|
let c = cases[i];
|
t.assertSwitchCase(c);
|
|
if (c.test) {
|
condition = t.conditionalExpression(
|
t.binaryExpression("===", t.cloneDeep(disc), c.test),
|
caseLocs[i] = this.loc(),
|
condition
|
);
|
} else {
|
caseLocs[i] = defaultLoc;
|
}
|
}
|
|
let discriminant = path.get("discriminant");
|
util.replaceWithOrRemove(discriminant, condition);
|
self.jump(self.explodeExpression(discriminant));
|
|
self.leapManager.withEntry(
|
new leap.SwitchEntry(after),
|
function() {
|
path.get("cases").forEach(function(casePath) {
|
let i = casePath.key;
|
self.mark(caseLocs[i]);
|
|
casePath.get("consequent").forEach(function (path) {
|
self.explodeStatement(path);
|
});
|
});
|
}
|
);
|
|
self.mark(after);
|
if (defaultLoc.value === -1) {
|
self.mark(defaultLoc);
|
assert.strictEqual(after.value, defaultLoc.value);
|
}
|
|
break;
|
|
case "IfStatement":
|
let elseLoc = stmt.alternate && this.loc();
|
after = this.loc();
|
|
self.jumpIfNot(
|
self.explodeExpression(path.get("test")),
|
elseLoc || after
|
);
|
|
self.explodeStatement(path.get("consequent"));
|
|
if (elseLoc) {
|
self.jump(after);
|
self.mark(elseLoc);
|
self.explodeStatement(path.get("alternate"));
|
}
|
|
self.mark(after);
|
|
break;
|
|
case "ReturnStatement":
|
self.emitAbruptCompletion({
|
type: "return",
|
value: self.explodeExpression(path.get("argument"))
|
});
|
|
break;
|
|
case "WithStatement":
|
throw new Error("WithStatement not supported in generator functions.");
|
|
case "TryStatement":
|
after = this.loc();
|
|
let handler = stmt.handler;
|
|
let catchLoc = handler && this.loc();
|
let catchEntry = catchLoc && new leap.CatchEntry(
|
catchLoc,
|
handler.param
|
);
|
|
let finallyLoc = stmt.finalizer && this.loc();
|
let finallyEntry = finallyLoc &&
|
new leap.FinallyEntry(finallyLoc, after);
|
|
let tryEntry = new leap.TryEntry(
|
self.getUnmarkedCurrentLoc(),
|
catchEntry,
|
finallyEntry
|
);
|
|
self.tryEntries.push(tryEntry);
|
self.updateContextPrevLoc(tryEntry.firstLoc);
|
|
self.leapManager.withEntry(tryEntry, function() {
|
self.explodeStatement(path.get("block"));
|
|
if (catchLoc) {
|
if (finallyLoc) {
|
// If we have both a catch block and a finally block, then
|
// because we emit the catch block first, we need to jump over
|
// it to the finally block.
|
self.jump(finallyLoc);
|
|
} else {
|
// If there is no finally block, then we need to jump over the
|
// catch block to the fall-through location.
|
self.jump(after);
|
}
|
|
self.updateContextPrevLoc(self.mark(catchLoc));
|
|
let bodyPath = path.get("handler.body");
|
let safeParam = self.makeTempVar();
|
self.clearPendingException(tryEntry.firstLoc, safeParam);
|
|
bodyPath.traverse(catchParamVisitor, {
|
getSafeParam: () => t.cloneDeep(safeParam),
|
catchParamName: handler.param.name
|
});
|
|
self.leapManager.withEntry(catchEntry, function() {
|
self.explodeStatement(bodyPath);
|
});
|
}
|
|
if (finallyLoc) {
|
self.updateContextPrevLoc(self.mark(finallyLoc));
|
|
self.leapManager.withEntry(finallyEntry, function() {
|
self.explodeStatement(path.get("finalizer"));
|
});
|
|
self.emit(t.returnStatement(t.callExpression(
|
self.contextProperty("finish"),
|
[finallyEntry.firstLoc]
|
)));
|
}
|
});
|
|
self.mark(after);
|
|
break;
|
|
case "ThrowStatement":
|
self.emit(t.throwStatement(
|
self.explodeExpression(path.get("argument"))
|
));
|
|
break;
|
|
case "ClassDeclaration":
|
self.emit(self.explodeClass(path));
|
break;
|
|
default:
|
throw new Error(
|
"unknown Statement of type " +
|
JSON.stringify(stmt.type));
|
}
|
};
|
|
let catchParamVisitor = {
|
Identifier: function(path, state) {
|
if (path.node.name === state.catchParamName && util.isReference(path)) {
|
util.replaceWithOrRemove(path, state.getSafeParam());
|
}
|
},
|
|
Scope: function(path, state) {
|
if (path.scope.hasOwnBinding(state.catchParamName)) {
|
// Don't descend into nested scopes that shadow the catch
|
// parameter with their own declarations.
|
path.skip();
|
}
|
}
|
};
|
|
Ep.emitAbruptCompletion = function(record) {
|
if (!isValidCompletion(record)) {
|
assert.ok(
|
false,
|
"invalid completion record: " +
|
JSON.stringify(record)
|
);
|
}
|
|
assert.notStrictEqual(
|
record.type, "normal",
|
"normal completions are not abrupt"
|
);
|
|
const t = util.getTypes();
|
let abruptArgs = [t.stringLiteral(record.type)];
|
|
if (record.type === "break" ||
|
record.type === "continue") {
|
t.assertLiteral(record.target);
|
abruptArgs[1] = this.insertedLocs.has(record.target)
|
? record.target
|
: t.cloneDeep(record.target);
|
} else if (record.type === "return" ||
|
record.type === "throw") {
|
if (record.value) {
|
t.assertExpression(record.value);
|
abruptArgs[1] = this.insertedLocs.has(record.value)
|
? record.value
|
: t.cloneDeep(record.value);
|
}
|
}
|
|
this.emit(
|
t.returnStatement(
|
t.callExpression(
|
this.contextProperty("abrupt"),
|
abruptArgs
|
)
|
)
|
);
|
};
|
|
function isValidCompletion(record) {
|
let type = record.type;
|
|
if (type === "normal") {
|
return !hasOwn.call(record, "target");
|
}
|
|
if (type === "break" ||
|
type === "continue") {
|
return !hasOwn.call(record, "value")
|
&& util.getTypes().isLiteral(record.target);
|
}
|
|
if (type === "return" ||
|
type === "throw") {
|
return hasOwn.call(record, "value")
|
&& !hasOwn.call(record, "target");
|
}
|
|
return false;
|
}
|
|
|
// Not all offsets into emitter.listing are potential jump targets. For
|
// example, execution typically falls into the beginning of a try block
|
// without jumping directly there. This method returns the current offset
|
// without marking it, so that a switch case will not necessarily be
|
// generated for this offset (I say "not necessarily" because the same
|
// location might end up being marked in the process of emitting other
|
// statements). There's no logical harm in marking such locations as jump
|
// targets, but minimizing the number of switch cases keeps the generated
|
// code shorter.
|
Ep.getUnmarkedCurrentLoc = function() {
|
return util.getTypes().numericLiteral(this.listing.length);
|
};
|
|
// The context.prev property takes the value of context.next whenever we
|
// evaluate the switch statement discriminant, which is generally good
|
// enough for tracking the last location we jumped to, but sometimes
|
// context.prev needs to be more precise, such as when we fall
|
// successfully out of a try block and into a finally block without
|
// jumping. This method exists to update context.prev to the freshest
|
// available location. If we were implementing a full interpreter, we
|
// would know the location of the current instruction with complete
|
// precision at all times, but we don't have that luxury here, as it would
|
// be costly and verbose to set context.prev before every statement.
|
Ep.updateContextPrevLoc = function(loc) {
|
const t = util.getTypes();
|
if (loc) {
|
t.assertLiteral(loc);
|
|
if (loc.value === -1) {
|
// If an uninitialized location literal was passed in, set its value
|
// to the current this.listing.length.
|
loc.value = this.listing.length;
|
} else {
|
// Otherwise assert that the location matches the current offset.
|
assert.strictEqual(loc.value, this.listing.length);
|
}
|
|
} else {
|
loc = this.getUnmarkedCurrentLoc();
|
}
|
|
// Make sure context.prev is up to date in case we fell into this try
|
// statement without jumping to it. TODO Consider avoiding this
|
// assignment when we know control must have jumped here.
|
this.emitAssign(this.contextProperty("prev"), loc);
|
};
|
|
|
// In order to save the rest of explodeExpression from a combinatorial
|
// trainwreck of special cases, explodeViaTempVar is responsible for
|
// deciding when a subexpression needs to be "exploded," which is my
|
// very technical term for emitting the subexpression as an assignment
|
// to a temporary variable and the substituting the temporary variable
|
// for the original subexpression. Think of exploded view diagrams, not
|
// Michael Bay movies. The point of exploding subexpressions is to
|
// control the precise order in which the generated code realizes the
|
// side effects of those subexpressions.
|
Ep.explodeViaTempVar = function(tempVar, childPath, hasLeapingChildren, ignoreChildResult) {
|
assert.ok(
|
!ignoreChildResult || !tempVar,
|
"Ignoring the result of a child expression but forcing it to " +
|
"be assigned to a temporary variable?"
|
);
|
const t = util.getTypes();
|
|
let result = this.explodeExpression(childPath, ignoreChildResult);
|
|
if (ignoreChildResult) {
|
// Side effects already emitted above.
|
|
} else if (tempVar || (hasLeapingChildren &&
|
!t.isLiteral(result))) {
|
// If tempVar was provided, then the result will always be assigned
|
// to it, even if the result does not otherwise need to be assigned
|
// to a temporary variable. When no tempVar is provided, we have
|
// the flexibility to decide whether a temporary variable is really
|
// necessary. Unfortunately, in general, a temporary variable is
|
// required whenever any child contains a yield expression, since it
|
// is difficult to prove (at all, let alone efficiently) whether
|
// this result would evaluate to the same value before and after the
|
// yield (see #206). One narrow case where we can prove it doesn't
|
// matter (and thus we do not need a temporary variable) is when the
|
// result in question is a Literal value.
|
result = this.emitAssign(
|
tempVar || this.makeTempVar(),
|
result
|
);
|
}
|
return result;
|
};
|
|
Ep.explodeExpression = function(path, ignoreResult) {
|
const t = util.getTypes();
|
let expr = path.node;
|
if (expr) {
|
t.assertExpression(expr);
|
} else {
|
return expr;
|
}
|
|
let self = this;
|
let result; // Used optionally by several cases below.
|
let after;
|
|
function finish(expr) {
|
t.assertExpression(expr);
|
if (ignoreResult) {
|
self.emit(expr);
|
}
|
return expr;
|
}
|
|
// If the expression does not contain a leap, then we either emit the
|
// expression as a standalone statement or return it whole.
|
if (!meta.containsLeap(expr)) {
|
return finish(expr);
|
}
|
|
// If any child contains a leap (such as a yield or labeled continue or
|
// break statement), then any sibling subexpressions will almost
|
// certainly have to be exploded in order to maintain the order of their
|
// side effects relative to the leaping child(ren).
|
let hasLeapingChildren = meta.containsLeap.onlyChildren(expr);
|
|
// If ignoreResult is true, then we must take full responsibility for
|
// emitting the expression with all its side effects, and we should not
|
// return a result.
|
|
switch (expr.type) {
|
case "MemberExpression":
|
return finish(t.memberExpression(
|
self.explodeExpression(path.get("object")),
|
expr.computed
|
? self.explodeViaTempVar(null, path.get("property"), hasLeapingChildren)
|
: expr.property,
|
expr.computed
|
));
|
|
case "CallExpression":
|
let calleePath = path.get("callee");
|
let argsPath = path.get("arguments");
|
|
let newCallee;
|
let newArgs;
|
|
let hasLeapingArgs = argsPath.some(
|
argPath => meta.containsLeap(argPath.node)
|
);
|
|
let injectFirstArg = null;
|
|
if (t.isMemberExpression(calleePath.node)) {
|
if (hasLeapingArgs) {
|
// If the arguments of the CallExpression contained any yield
|
// expressions, then we need to be sure to evaluate the callee
|
// before evaluating the arguments, but if the callee was a member
|
// expression, then we must be careful that the object of the
|
// member expression still gets bound to `this` for the call.
|
|
let newObject = self.explodeViaTempVar(
|
// Assign the exploded callee.object expression to a temporary
|
// variable so that we can use it twice without reevaluating it.
|
self.makeTempVar(),
|
calleePath.get("object"),
|
hasLeapingChildren
|
);
|
|
let newProperty = calleePath.node.computed
|
? self.explodeViaTempVar(null, calleePath.get("property"), hasLeapingChildren)
|
: calleePath.node.property;
|
|
injectFirstArg = newObject;
|
|
newCallee = t.memberExpression(
|
t.memberExpression(
|
t.cloneDeep(newObject),
|
newProperty,
|
calleePath.node.computed
|
),
|
t.identifier("call"),
|
false
|
);
|
|
} else {
|
newCallee = self.explodeExpression(calleePath);
|
}
|
|
} else {
|
newCallee = self.explodeViaTempVar(null, calleePath, hasLeapingChildren);
|
|
if (t.isMemberExpression(newCallee)) {
|
// If the callee was not previously a MemberExpression, then the
|
// CallExpression was "unqualified," meaning its `this` object
|
// should be the global object. If the exploded expression has
|
// become a MemberExpression (e.g. a context property, probably a
|
// temporary variable), then we need to force it to be unqualified
|
// by using the (0, object.property)(...) trick; otherwise, it
|
// will receive the object of the MemberExpression as its `this`
|
// object.
|
newCallee = t.sequenceExpression([
|
t.numericLiteral(0),
|
t.cloneDeep(newCallee)
|
]);
|
}
|
}
|
|
if (hasLeapingArgs) {
|
newArgs = argsPath.map(argPath => self.explodeViaTempVar(null, argPath, hasLeapingChildren));
|
if (injectFirstArg) newArgs.unshift(injectFirstArg);
|
|
newArgs = newArgs.map(arg => t.cloneDeep(arg));
|
} else {
|
newArgs = path.node.arguments;
|
}
|
|
return finish(t.callExpression(newCallee, newArgs));
|
|
case "NewExpression":
|
return finish(t.newExpression(
|
self.explodeViaTempVar(null, path.get("callee"), hasLeapingChildren),
|
path.get("arguments").map(function(argPath) {
|
return self.explodeViaTempVar(null, argPath, hasLeapingChildren);
|
})
|
));
|
|
case "ObjectExpression":
|
return finish(t.objectExpression(
|
path.get("properties").map(function(propPath) {
|
if (propPath.isObjectProperty()) {
|
return t.objectProperty(
|
propPath.node.key,
|
self.explodeViaTempVar(null, propPath.get("value"), hasLeapingChildren),
|
propPath.node.computed
|
);
|
} else {
|
return propPath.node;
|
}
|
})
|
));
|
|
case "ArrayExpression":
|
return finish(t.arrayExpression(
|
path.get("elements").map(function(elemPath) {
|
if (!elemPath.node) {
|
return null;
|
} if (elemPath.isSpreadElement()) {
|
return t.spreadElement(
|
self.explodeViaTempVar(null, elemPath.get("argument"), hasLeapingChildren)
|
);
|
} else {
|
return self.explodeViaTempVar(null, elemPath, hasLeapingChildren);
|
}
|
})
|
));
|
|
case "SequenceExpression":
|
let lastIndex = expr.expressions.length - 1;
|
|
path.get("expressions").forEach(function(exprPath) {
|
if (exprPath.key === lastIndex) {
|
result = self.explodeExpression(exprPath, ignoreResult);
|
} else {
|
self.explodeExpression(exprPath, true);
|
}
|
});
|
|
return result;
|
|
case "LogicalExpression":
|
after = this.loc();
|
|
if (!ignoreResult) {
|
result = self.makeTempVar();
|
}
|
|
let left = self.explodeViaTempVar(result, path.get("left"), hasLeapingChildren);
|
|
if (expr.operator === "&&") {
|
self.jumpIfNot(left, after);
|
} else {
|
assert.strictEqual(expr.operator, "||");
|
self.jumpIf(left, after);
|
}
|
|
self.explodeViaTempVar(result, path.get("right"), hasLeapingChildren, ignoreResult);
|
|
self.mark(after);
|
|
return result;
|
|
case "ConditionalExpression":
|
let elseLoc = this.loc();
|
after = this.loc();
|
let test = self.explodeExpression(path.get("test"));
|
|
self.jumpIfNot(test, elseLoc);
|
|
if (!ignoreResult) {
|
result = self.makeTempVar();
|
}
|
|
self.explodeViaTempVar(result, path.get("consequent"), hasLeapingChildren, ignoreResult);
|
self.jump(after);
|
|
self.mark(elseLoc);
|
self.explodeViaTempVar(result, path.get("alternate"), hasLeapingChildren, ignoreResult);
|
|
self.mark(after);
|
|
return result;
|
|
case "UnaryExpression":
|
return finish(t.unaryExpression(
|
expr.operator,
|
// Can't (and don't need to) break up the syntax of the argument.
|
// Think about delete a[b].
|
self.explodeExpression(path.get("argument")),
|
!!expr.prefix
|
));
|
|
case "BinaryExpression":
|
return finish(t.binaryExpression(
|
expr.operator,
|
self.explodeViaTempVar(null, path.get("left"), hasLeapingChildren),
|
self.explodeViaTempVar(null, path.get("right"), hasLeapingChildren)
|
));
|
|
case "AssignmentExpression":
|
if (expr.operator === "=") {
|
// If this is a simple assignment, the left hand side does not need
|
// to be read before the right hand side is evaluated, so we can
|
// avoid the more complicated logic below.
|
return finish(t.assignmentExpression(
|
expr.operator,
|
self.explodeExpression(path.get("left")),
|
self.explodeExpression(path.get("right"))
|
));
|
}
|
|
const lhs = self.explodeExpression(path.get("left"));
|
const temp = self.emitAssign(self.makeTempVar(), lhs);
|
|
// For example,
|
//
|
// x += yield y
|
//
|
// becomes
|
//
|
// context.t0 = x
|
// x = context.t0 += yield y
|
//
|
// so that the left-hand side expression is read before the yield.
|
// Fixes https://github.com/facebook/regenerator/issues/345.
|
|
return finish(t.assignmentExpression(
|
"=",
|
t.cloneDeep(lhs),
|
t.assignmentExpression(
|
expr.operator,
|
t.cloneDeep(temp),
|
self.explodeExpression(path.get("right"))
|
)
|
));
|
|
case "UpdateExpression":
|
return finish(t.updateExpression(
|
expr.operator,
|
self.explodeExpression(path.get("argument")),
|
expr.prefix
|
));
|
|
case "YieldExpression":
|
after = this.loc();
|
let arg = expr.argument && self.explodeExpression(path.get("argument"));
|
|
if (arg && expr.delegate) {
|
let result = self.makeTempVar();
|
|
let ret = t.returnStatement(t.callExpression(
|
self.contextProperty("delegateYield"),
|
[
|
arg,
|
t.stringLiteral(result.property.name),
|
after
|
]
|
));
|
ret.loc = expr.loc;
|
|
self.emit(ret);
|
self.mark(after);
|
|
return result;
|
}
|
|
self.emitAssign(self.contextProperty("next"), after);
|
|
let ret = t.returnStatement(t.cloneDeep(arg) || null);
|
// Preserve the `yield` location so that source mappings for the statements
|
// link back to the yield properly.
|
ret.loc = expr.loc;
|
self.emit(ret);
|
self.mark(after);
|
|
return self.contextProperty("sent");
|
|
case "ClassExpression":
|
return finish(self.explodeClass(path));
|
|
default:
|
throw new Error(
|
"unknown Expression of type " +
|
JSON.stringify(expr.type));
|
}
|
};
|
|
Ep.explodeClass = function(path) {
|
const explodingChildren = [];
|
|
if (path.node.superClass) {
|
explodingChildren.push(path.get("superClass"));
|
}
|
|
path.get("body.body").forEach(member => {
|
if (member.node.computed) {
|
explodingChildren.push(member.get("key"));
|
}
|
});
|
|
const hasLeapingChildren = explodingChildren.some(
|
child => meta.containsLeap(child));
|
|
for (let i = 0; i < explodingChildren.length; i++) {
|
const child = explodingChildren[i];
|
const isLast = i === explodingChildren.length - 1;
|
|
if (isLast) {
|
child.replaceWith(this.explodeExpression(child));
|
} else {
|
child.replaceWith(this.explodeViaTempVar(null, child, hasLeapingChildren));
|
}
|
}
|
|
return path.node;
|
};
|
