/*
* Copyright 2014 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import com.google.common.base.Preconditions;
import com.google.javascript.jscomp.parsing.JsDocInfoParser;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfoBuilder;
import com.google.javascript.rhino.JSTypeExpression;
import com.google.javascript.rhino.Node;
/**
* Helper class for transpiling ES6 template literals.
*
* @author moz@google.com (Michael Zhou)
*/
class Es6TemplateLiterals {
private static final String TEMPLATELIT_VAR = "$jscomp$templatelit$";
/**
* Converts `${a} b ${c} d ${e}` to (a + " b " + c + " d " + e)
*
* @param n A TEMPLATELIT node that is not prefixed with a tag
*/
static void visitTemplateLiteral(NodeTraversal t, Node n) {
int length = n.getChildCount();
if (length == 0) {
n.replaceWith(IR.string("\"\""));
} else {
Node first = n.removeFirstChild();
Preconditions.checkState(first.isString());
if (length == 1) {
n.replaceWith(first);
} else {
// Add the first string with the first substitution expression
Node add = IR.add(first, n.removeFirstChild().removeFirstChild());
// Process the rest of the template literal
for (int i = 2; i < length; i++) {
Node child = n.removeFirstChild();
if (child.isString()) {
if (child.getString().isEmpty()) {
continue;
} else if (i == 2 && first.getString().isEmpty()) {
// So that `${hello} world` gets translated into (hello + " world")
// instead of ("" + hello + " world").
add = add.getSecondChild().detach();
}
}
add = IR.add(add, child.isString() ? child : child.removeFirstChild());
}
n.replaceWith(add.useSourceInfoIfMissingFromForTree(n));
}
}
t.reportCodeChange();
}
/**
* Converts tag`a\tb${bar}` to:
* // A global (module) scoped variable
* var $jscomp$templatelit$0 = ["a\tb"]; // cooked string array
* $jscomp$templatelit$0.raw = ["a\\tb"]; // raw string array
* ...
* // A call to the tagging function
* tag($jscomp$templatelit$0, bar);
*
* See template_literal_test.js for more examples.
*
* @param n A TAGGED_TEMPLATELIT node
*/
static void visitTaggedTemplateLiteral(NodeTraversal t, Node n) {
Node templateLit = n.getLastChild();
// Prepare the raw and cooked string arrays.
Node raw = createRawStringArray(templateLit);
Node cooked = createCookedStringArray(templateLit);
// Specify the type of the first argument to be ITemplateArray.
JSTypeExpression nonNullSiteObject = new JSTypeExpression(
JsDocInfoParser.parseTypeString("!ITemplateArray"), "<Es6TemplateLiterals.java>");
JSDocInfoBuilder info = new JSDocInfoBuilder(false);
info.recordType(nonNullSiteObject);
Node siteObject = IR.cast(cooked, info.build());
// Create a variable representing the template literal.
Node callsiteId = IR.name(
TEMPLATELIT_VAR + t.getCompiler().getUniqueNameIdSupplier().get());
Node var = IR.var(callsiteId, siteObject).useSourceInfoIfMissingFromForTree(n);
Node script = NodeUtil.getEnclosingScript(n);
script.addChildToFront(var);
// Define the "raw" property on the introduced variable.
Node defineRaw = IR.exprResult(IR.assign(IR.getprop(
callsiteId.cloneNode(), IR.string("raw")), raw))
.useSourceInfoIfMissingFromForTree(n);
script.addChildAfter(defineRaw, var);
// Generate the call expression.
Node call = IR.call(n.removeFirstChild(), callsiteId.cloneNode());
for (Node child = templateLit.getFirstChild(); child != null; child = child.getNext()) {
if (!child.isString()) {
call.addChildToBack(child.removeFirstChild());
}
}
call.useSourceInfoIfMissingFromForTree(templateLit);
call.putBooleanProp(Node.FREE_CALL, !call.getFirstChild().isGetProp());
n.replaceWith(call);
t.reportCodeChange();
}
private static Node createRawStringArray(Node n) {
Node array = IR.arraylit();
for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
if (child.isString()) {
array.addChildToBack(IR.string((String) child.getProp(Node.RAW_STRING_VALUE)));
}
}
return array;
}
private static Node createCookedStringArray(Node n) {
Node array = IR.arraylit();
for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
if (child.isString()) {
Node string = IR.string(cookString((String) child.getProp(Node.RAW_STRING_VALUE)));
array.addChildToBack(string);
}
}
return array;
}
/**
* Takes a raw string and returns a string that is suitable for the cooked
* value (the Template Value or TV as described in the specs). This involves
* removing line continuations.
*/
private static String cookString(String s) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length();) {
char c = s.charAt(i++);
if (c == '\\') {
char c2 = s.charAt(i++);
switch (c2) {
case 't':
sb.append('\t');
break;
case 'n':
sb.append('\n');
break;
case 'r':
sb.append('\r');
break;
case 'f':
sb.append('\f');
break;
case 'b':
sb.append('\b');
break;
case 'u':
int unicodeValue = Integer.parseInt(s.substring(i, i + 4), 16);
sb.append((char) unicodeValue);
i += 4;
break;
// Strip line continuation.
case '\n':
case '\u2028':
case '\u2029':
break;
case '\r':
// \ \r \n should be stripped as one
if (s.charAt(i + 1) == '\n') {
i++;
}
break;
default:
sb.append(c);
sb.append(c2);
}
} else {
sb.append(c);
}
}
return sb.toString();
}
}