Page MenuHomec4science
Files F90768728

hoist.js
No OneTemporary
Actions

File Metadata

Created
Mon, Nov 4, 14:13

hoist.js
View Options

/**
* 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 * as util from "./util";
let hasOwn = Object.prototype.hasOwnProperty;
// The hoist function takes a FunctionExpression or FunctionDeclaration
// and replaces any Declaration nodes in its body with assignments, then
// returns a VariableDeclaration containing just the names of the removed
// declarations.
exports.hoist = function(funPath) {
const t = util.getTypes();
t.assertFunction(funPath.node);
let vars = {};
function varDeclToExpr({ node: vdec, scope }, includeIdentifiers) {
t.assertVariableDeclaration(vdec);
// TODO assert.equal(vdec.kind, "var");
let exprs = [];
vdec.declarations.forEach(function(dec) {
// Note: We duplicate 'dec.id' here to ensure that the variable declaration IDs don't
// have the same 'loc' value, since that can make sourcemaps and retainLines behave poorly.
vars[dec.id.name] = t.identifier(dec.id.name);
// Remove the binding, to avoid "duplicate declaration" errors when it will
// be injected again.
scope.removeBinding(dec.id.name);
if (dec.init) {
exprs.push(t.assignmentExpression(
"=", dec.id, dec.init
));
} else if (includeIdentifiers) {
exprs.push(dec.id);
}
});
if (exprs.length === 0)
return null;
if (exprs.length === 1)
return exprs[0];
return t.sequenceExpression(exprs);
}
funPath.get("body").traverse({
VariableDeclaration: {
exit: function(path) {
let expr = varDeclToExpr(path, false);
if (expr === null) {
path.remove();
} else {
// We don't need to traverse this expression any further because
// there can't be any new declarations inside an expression.
util.replaceWithOrRemove(path, t.expressionStatement(expr));
}
// Since the original node has been either removed or replaced,
// avoid traversing it any further.
path.skip();
}
},
ForStatement: function(path) {
let init = path.get("init");
if (init.isVariableDeclaration()) {
util.replaceWithOrRemove(init, varDeclToExpr(init, false));
}
},
ForXStatement: function(path) {
let left = path.get("left");
if (left.isVariableDeclaration()) {
util.replaceWithOrRemove(left, varDeclToExpr(left, true));
}
},
FunctionDeclaration: function(path) {
let node = path.node;
vars[node.id.name] = node.id;
let assignment = t.expressionStatement(
t.assignmentExpression(
"=",
t.clone(node.id),
t.functionExpression(
path.scope.generateUidIdentifierBasedOnNode(node),
node.params,
node.body,
node.generator,
node.expression
)
)
);
if (path.parentPath.isBlockStatement()) {
// Insert the assignment form before the first statement in the
// enclosing block.
path.parentPath.unshiftContainer("body", assignment);
// Remove the function declaration now that we've inserted the
// equivalent assignment form at the beginning of the block.
path.remove();
} else {
// If the parent node is not a block statement, then we can just
// replace the declaration with the equivalent assignment form
// without worrying about hoisting it.
util.replaceWithOrRemove(path, assignment);
}
// Remove the binding, to avoid "duplicate declaration" errors when it will
// be injected again.
path.scope.removeBinding(node.id.name);
// Don't hoist variables out of inner functions.
path.skip();
},
FunctionExpression: function(path) {
// Don't descend into nested function expressions.
path.skip();
},
ArrowFunctionExpression: function(path) {
// Don't descend into nested function expressions.
path.skip();
}
});
let paramNames = {};
funPath.get("params").forEach(function(paramPath) {
let param = paramPath.node;
if (t.isIdentifier(param)) {
paramNames[param.name] = param;
} else {
// Variables declared by destructuring parameter patterns will be
// harmlessly re-declared.
}
});
let declarations = [];
Object.keys(vars).forEach(function(name) {
if (!hasOwn.call(paramNames, name)) {
declarations.push(t.variableDeclarator(vars[name], null));
}
});
if (declarations.length === 0) {
return null; // Be sure to handle this case!
}
return t.variableDeclaration("var", declarations);
};

Event Timeline

c4science · Help