Closes eslint-community#28 - default mapping of sourc .ts import of unspecified extension should be .js

Author: rosskevin

.gitignore

@@ -4,3 +4,4 @@
 /node_modules
 /test.js
 .eslintcache
+.vscode

lib/util/map-typescript-extension.js

@@ -4,6 +4,7 @@ const path = require("path")
 const isTypescript = require("../util/is-typescript")
 
 const mapping = {
+    "": ".js", // default empty extension will map to js
     ".ts": ".js",
     ".cts": ".cjs",
     ".mts": ".mjs",

tests/lib/rules/file-extension-in-import.js

@@ -73,6 +73,10 @@ new RuleTester({
             filename: fixture("test.js"),
             code: "import './d.js'",
         },
+        {
+            filename: fixture("test.ts"),
+            code: "import './a.js'",
+        },
         {
             filename: fixture("test.ts"),
             code: "import './d.js'",
@@ -145,6 +149,18 @@ new RuleTester({
             output: "import './a.js'",
             errors: [{ messageId: "requireExt", data: { ext: ".js" } }],
         },
+        {
+            filename: fixture("test.ts"),
+            code: "import './a'",
+            output: "import './a.js'",
+            errors: [{ messageId: "requireExt", data: { ext: ".js" } }],
+        },
+        {
+            filename: fixture("test.ts"),
+            code: "import './d'",
+            output: "import './d.js'",
+            errors: [{ messageId: "requireExt", data: { ext: ".js" } }],
+        },
         {
             filename: fixture("test.js"),
             code: "import './b'",