Add babelrc.json support (#10783)

* Add babelrc.json support

* Add tests

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

packages/babel-core/src/config/files/configuration.js

@@ -32,6 +32,7 @@ const RELATIVE_CONFIG_FILENAMES = [
   ".babelrc.js",
   ".babelrc.cjs",
   ".babelrc.mjs",
+  ".babelrc.json",
 ];
 
 const BABELIGNORE_FILENAME = ".babelignore";

packages/babel-core/test/config-chain.js

@@ -1076,9 +1076,13 @@ describe("buildConfigChain", function() {
     });
 
     describe("relative", () => {
-      test.each(["package.json", ".babelrc", ".babelrc.js", ".babelrc.cjs"])(
-        "should load %s synchronously",
-        async name => {
+      test.each([
+        "package.json",
+        ".babelrc",
+        ".babelrc.js",
+        ".babelrc.cjs",
+        ".babelrc.json",
+      ])("should load %s synchronously", async name => {
         const { cwd, tmp, config } = await getTemp(
           `babel-test-load-config-${name}`,
         );
@@ -1093,8 +1097,7 @@ describe("buildConfigChain", function() {
           root: cwd,
           comments: true,
         });
-        },
-      );
+      });
 
       test("should not load .babelrc.mjs synchronously", async () => {
         const { cwd, tmp, config } = await getTemp(
@@ -1147,6 +1150,7 @@ describe("buildConfigChain", function() {
           ".babelrc.js",
           ".babelrc.cjs",
           ".babelrc.mjs",
+          ".babelrc.json",
         ]),
       )("should throw if both %s and %s are used", async (name1, name2) => {
         const { cwd, tmp, config } = await getTemp(
@@ -1175,6 +1179,7 @@ describe("buildConfigChain", function() {
       test.each`
         config             | dir                     | error
         ${".babelrc"}      | ${"babelrc-error"}      | ${/Error while parsing config - /}
+        ${".babelrc.json"} | ${"babelrc-json-error"} | ${/Error while parsing config - /}
         ${".babelrc.js"}   | ${"babelrc-js-error"}   | ${/Babelrc threw an error/}
         ${".babelrc.cjs"}  | ${"babelrc-cjs-error"}  | ${/Babelrc threw an error/}
         ${".babelrc.mjs"}  | ${"babelrc-mjs-error"}  | ${/Babelrc threw an error/}

packages/babel-core/test/fixtures/config/config-files-templates/.babelrc.json

@@ -0,0 +1,3 @@
+{
+  "comments": true
+}

packages/babel-core/test/fixtures/config/config-files/babelrc-json-error/.babelrc

@@ -0,0 +1 @@
+{45