/**
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* Copyright (c) 2014-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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import * as util from "./util";
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let hasOwn = Object.prototype.hasOwnProperty;
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// The hoist function takes a FunctionExpression or FunctionDeclaration
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// and replaces any Declaration nodes in its body with assignments, then
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// returns a VariableDeclaration containing just the names of the removed
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// declarations.
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exports.hoist = function(funPath) {
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const t = util.getTypes();
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t.assertFunction(funPath.node);
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let vars = {};
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function varDeclToExpr({ node: vdec, scope }, includeIdentifiers) {
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t.assertVariableDeclaration(vdec);
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// TODO assert.equal(vdec.kind, "var");
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let exprs = [];
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vdec.declarations.forEach(function(dec) {
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// Note: We duplicate 'dec.id' here to ensure that the variable declaration IDs don't
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// have the same 'loc' value, since that can make sourcemaps and retainLines behave poorly.
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vars[dec.id.name] = t.identifier(dec.id.name);
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// Remove the binding, to avoid "duplicate declaration" errors when it will
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// be injected again.
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scope.removeBinding(dec.id.name);
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if (dec.init) {
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exprs.push(t.assignmentExpression(
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"=", dec.id, dec.init
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));
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} else if (includeIdentifiers) {
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exprs.push(dec.id);
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}
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});
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if (exprs.length === 0)
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return null;
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if (exprs.length === 1)
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return exprs[0];
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return t.sequenceExpression(exprs);
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}
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funPath.get("body").traverse({
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VariableDeclaration: {
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exit: function(path) {
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let expr = varDeclToExpr(path, false);
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if (expr === null) {
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path.remove();
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} else {
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// We don't need to traverse this expression any further because
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// there can't be any new declarations inside an expression.
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util.replaceWithOrRemove(path, t.expressionStatement(expr));
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}
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// Since the original node has been either removed or replaced,
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// avoid traversing it any further.
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path.skip();
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}
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},
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ForStatement: function(path) {
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let init = path.get("init");
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if (init.isVariableDeclaration()) {
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util.replaceWithOrRemove(init, varDeclToExpr(init, false));
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}
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},
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ForXStatement: function(path) {
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let left = path.get("left");
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if (left.isVariableDeclaration()) {
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util.replaceWithOrRemove(left, varDeclToExpr(left, true));
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}
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},
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FunctionDeclaration: function(path) {
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let node = path.node;
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vars[node.id.name] = node.id;
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let assignment = t.expressionStatement(
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t.assignmentExpression(
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"=",
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t.clone(node.id),
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t.functionExpression(
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path.scope.generateUidIdentifierBasedOnNode(node),
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node.params,
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node.body,
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node.generator,
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node.expression
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)
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)
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);
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if (path.parentPath.isBlockStatement()) {
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// Insert the assignment form before the first statement in the
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// enclosing block.
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path.parentPath.unshiftContainer("body", assignment);
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// Remove the function declaration now that we've inserted the
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// equivalent assignment form at the beginning of the block.
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path.remove();
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} else {
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// If the parent node is not a block statement, then we can just
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// replace the declaration with the equivalent assignment form
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// without worrying about hoisting it.
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util.replaceWithOrRemove(path, assignment);
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}
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// Remove the binding, to avoid "duplicate declaration" errors when it will
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// be injected again.
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path.scope.removeBinding(node.id.name);
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// Don't hoist variables out of inner functions.
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path.skip();
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},
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FunctionExpression: function(path) {
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// Don't descend into nested function expressions.
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path.skip();
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},
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ArrowFunctionExpression: function(path) {
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// Don't descend into nested function expressions.
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path.skip();
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}
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});
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let paramNames = {};
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funPath.get("params").forEach(function(paramPath) {
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let param = paramPath.node;
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if (t.isIdentifier(param)) {
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paramNames[param.name] = param;
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} else {
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// Variables declared by destructuring parameter patterns will be
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// harmlessly re-declared.
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}
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});
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let declarations = [];
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Object.keys(vars).forEach(function(name) {
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if (!hasOwn.call(paramNames, name)) {
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declarations.push(t.variableDeclarator(vars[name], null));
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}
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});
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if (declarations.length === 0) {
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return null; // Be sure to handle this case!
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}
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return t.variableDeclaration("var", declarations);
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};
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