Use babylon.parseExpression for JSON (#2476)

* Add comments showing parser arguments

Since this is how they are invoked, the comments make it easier to maintain.

* Use babylon.parseExpression for JSON

See https://github.com/prettier/prettier/issues/2378#issuecomment-314600778

Note that this doesn't yet print comments:

    echo '{/*comment*/"K":"V"}' | ./bin/prettier.js --parser json

* Remove parser-json.js

This reduces duplicate code in the built package.
See https://github.com/prettier/prettier/pull/2476#pullrequestreview-50181398

* Add test with block comment in JSON

* Fix test with block comment in JSON

* Add test with line comment in JSON

* Don't build now-redundant parser-json.js

src/parser-babylon.js

@@ -2,7 +2,7 @@
 
 const createError = require("./parser-create-error");
 
-function parse(text) {
+function parse(text, parsers, opts) {
   // Inline the require to avoid loading all the JS if we don't use it
   const babylon = require("babylon");
 
@@ -27,12 +27,15 @@ function parse(text) {
     ]
   };
 
+  const parseMethod =
+    opts && opts.parser === "json" ? "parseExpression" : "parse";
+
   let ast;
   try {
-    ast = babylon.parse(text, babylonOptions);
+    ast = babylon[parseMethod](text, babylonOptions);
   } catch (originalError) {
     try {
-      ast = babylon.parse(
+      ast = babylon[parseMethod](
         text,
         Object.assign({}, babylonOptions, { strictMode: false })
       );

src/parser-flow.js

@@ -3,7 +3,7 @@
 const createError = require("./parser-create-error");
 const includeShebang = require("./parser-include-shebang");
 
-function parse(text) {
+function parse(text /*, parsers, opts*/) {
   // Fixes Node 4 issue (#1986)
   "use strict"; // eslint-disable-line
   // Inline the require to avoid loading all the JS if we don't use it

src/parser-graphql.js

@@ -34,7 +34,7 @@ function removeTokens(node) {
   return node;
 }
 
-function parse(text) {
+function parse(text /*, parsers, opts*/) {
   // Inline the require to avoid loading all the JS if we don't use it
   const parser = require("graphql/language");
   try {

src/parser-json.js

@@ -1,82 +0,0 @@
-"use strict";
-
-const createError = require("./parser-create-error");
-
-function parse(text) {
-  const jsonToAst = require("json-to-ast");
-  try {
-    const ast = jsonToAst(text);
-    return toBabylon(ast);
-  } catch (err) {
-    const firstNewlineIndex = err.message.indexOf("\n");
-    const firstLine = err.message.slice(0, firstNewlineIndex);
-    const lastSpaceIndex = firstLine.lastIndexOf(" ");
-    const message = firstLine.slice(0, lastSpaceIndex);
-    const locString = firstLine.slice(lastSpaceIndex + 1);
-    const lineCol = locString.split(":").map(Number);
-
-    throw createError("(json-to-ast) " + message, {
-      start: {
-        line: lineCol[0],
-        column: lineCol[1]
-      }
-    });
-  }
-}
-
-function toBabylon(node) {
-  const typeMap = {
-    object: "ObjectExpression",
-    property: "ObjectProperty",
-    identifier: "json-identifier",
-    array: "ArrayExpression"
-  };
-
-  const result = {
-    type: typeMap[node.type],
-    start: node.loc.start.offset,
-    end: node.loc.end.offset,
-    loc: node.loc
-  };
-
-  switch (node.type) {
-    case "object":
-      return Object.assign(result, {
-        properties: node.children.map(toBabylon)
-      });
-    case "property":
-      return Object.assign(result, {
-        key: toBabylon(node.key),
-        value: toBabylon(node.value)
-      });
-    case "identifier":
-      return Object.assign(result, {
-        value: node.value
-      });
-    case "array":
-      return Object.assign(result, {
-        elements: node.children.map(toBabylon)
-      });
-    case "literal": {
-      const constructorTypes = {
-        String: "StringLiteral",
-        Number: "NumericLiteral",
-        Boolean: "BooleanLiteral"
-      };
-
-      const value = JSON.parse(node.rawValue);
-      const type =
-        value === null
-          ? "NullLiteral"
-          : constructorTypes[value.constructor.name];
-
-      return Object.assign(result, {
-        type: type,
-        value: value,
-        extra: { raw: node.rawValue }
-      });
-    }
-  }
-}
-
-module.exports = parse;

src/parser-parse5.js

@@ -2,7 +2,7 @@
 
 // const createError = require("./parser-create-error");
 
-function parse(text) {
+function parse(text /*, parsers, opts*/) {
   // Inline the require to avoid loading all the JS if we don't use it
   const parse5 = require("parse5");
   try {

src/parser-postcss.js

@@ -208,7 +208,7 @@ function requireParser(isSCSS) {
   return require("postcss-less");
 }
 
-function parse(text) {
+function parse(text /*, parsers, opts*/) {
   const isLikelySCSS = !!text.match(/(\w\s*: [^}:]+|#){|@import[^\n]+(url|,)/);
   try {
     return parseWithParser(requireParser(isLikelySCSS), text);

src/parser-typescript.js

@@ -3,7 +3,7 @@
 const createError = require("./parser-create-error");
 const includeShebang = require("./parser-include-shebang");
 
-function parse(text) {
+function parse(text /*, parsers, opts*/) {
   const jsx = isProbablyJsx(text);
   let ast;
   try {

src/parser.js

@@ -22,7 +22,7 @@ const parsers = {
     return eval("require")("./parser-postcss");
   },
   get json() {
-    return eval("require")("./parser-json");
+    return eval("require")("./parser-babylon");
   }
 };
 

src/printer.js

@@ -2636,8 +2636,6 @@ function genericPrintNoParens(path, options, print, args) {
       return path.call(bodyPath => {
         return printStatementSequence(bodyPath, options, print);
       }, "body");
-    case "json-identifier":
-      return '"' + n.value + '"';
 
     default:
       /* istanbul ignore next */
@@ -2709,7 +2707,12 @@ function printPropertyKey(path, options, print) {
   const node = path.getNode();
   const key = node.key;
 
-  if (isStringLiteral(key) && isIdentifierName(key.value) && !node.computed) {
+  if (
+    isStringLiteral(key) &&
+    isIdentifierName(key.value) &&
+    !node.computed &&
+    options.parser !== "json"
+  ) {
     // 'a' -> a
     return path.call(
       keyPath => comments.printComments(keyPath, () => key.value, options),