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74 lines
2.2 KiB
JavaScript
74 lines
2.2 KiB
JavaScript
/**
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* Copyright 2013 Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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var recast = require('recast');
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exports.propagate = function(constants, source) {
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var ast = recast.parse(source);
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ast = new ConstantVisitor(constants).visit(ast);
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return recast.print(ast);
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};
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var ConstantVisitor = recast.Visitor.extend({
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init: function(constants) {
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this.constants = constants || {};
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},
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visitIdentifier: function(ident) {
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if (this.constants.hasOwnProperty(ident.name)) {
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return recast.builder.literal(this.constants[ident.name]);
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}
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},
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visitCallExpression: function(call) {
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if (!this.constants.__DEV__) {
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if (call.callee.type === 'Identifier' && call.callee.name === 'invariant') {
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call.arguments.length = 1;
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}
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}
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this.genericVisit(call);
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},
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visitIfStatement: function(stmt) {
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// Replaces all identifiers in this.constants with literal values.
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this.genericVisit(stmt);
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if (stmt.test.type === recast.Syntax.Literal) {
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if (stmt.test.value) {
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stmt.alternate = null;
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} else if (stmt.alternate) {
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return stmt.alternate;
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} else {
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// In case this if statement is an alternate clause for another
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// if-statement, replacing that alternate with null will have the
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// effect of pruning the unnecessary clause. If this is just a
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// free-floating if statement, replacing it with null will have
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// the effect of removing it from the enclosing list of
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// statements.
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return null;
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}
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}
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}
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});
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if (!module.parent) {
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var constants = JSON.parse(process.argv[3]);
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recast.run(function(ast, callback) {
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callback(new ConstantVisitor(constants).visit(ast));
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});
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}
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