Add support for resolving extensions in relative paths

src/resolvePath.js

@@ -17,6 +17,20 @@ function getRelativePath(sourcePath, currentFile, absFileInRoot, opts) {
   return toLocalPath(toPosixPath(relativePath));
 }
 
+function resolvePathFromRelativeConfig(sourcePath, currentFile, opts) {
+  if (!isRelativePath(sourcePath)) {
+    return null;
+  }
+
+  const absFileInRoot = nodeResolvePath(sourcePath, path.dirname(currentFile), opts.extensions);
+
+  if (!absFileInRoot) {
+    return null;
+  }
+
+  return getRelativePath(sourcePath, currentFile, absFileInRoot, opts);
+}
+
 function findPathInRoots(sourcePath, { extensions, root }) {
   // Search the source path inside every custom root directory
   let resolvedSourceFile;
@@ -78,15 +92,12 @@ function resolvePathFromAliasConfig(sourcePath, currentFile, opts) {
 }
 
 const resolvers = [
+  resolvePathFromRelativeConfig,
   resolvePathFromAliasConfig,
   resolvePathFromRootConfig,
 ];
 
 export default function resolvePath(sourcePath, currentFile, opts) {
-  if (isRelativePath(sourcePath)) {
-    return sourcePath;
-  }
-
   const normalizedOpts = normalizeOptions(currentFile, opts);
 
   // File param is a relative path from the environment current working directory

test/index.test.js

@@ -298,6 +298,14 @@ describe('module-resolver', () => {
           rootTransformerOpts,
         );
       });
+
+      it('should resolve the relative file path with a known defined extension', () => {
+        testWithImport(
+          './test/testproject/src/rn/file',
+          './test/testproject/src/rn/file.android.js',
+          rootTransformerOpts,
+        );
+      });
     });
 
     describe('root and alias', () => {
@@ -321,6 +329,28 @@ describe('module-resolver', () => {
         );
       });
     });
+
+    describe('with the plugin applied twice', () => {
+      const doubleAliasTransformerOpts = {
+        babelrc: false,
+        plugins: [
+          [plugin, { root: '.' }],
+          [plugin, {
+            alias: {
+              '^@namespace/foo-(.+)': './packages/\\1',
+            },
+          }],
+        ],
+      };
+
+      it('should support replacing parts of a path', () => {
+        testWithImport(
+          '@namespace/foo-bar',
+          './packages/bar',
+          doubleAliasTransformerOpts,
+        );
+      });
+    });
   });
 
   describe('alias', () => {
@@ -590,28 +620,6 @@ describe('module-resolver', () => {
       });
     });
 
-    describe('with the plugin applied twice', () => {
-      const doubleAliasTransformerOpts = {
-        babelrc: false,
-        plugins: [
-          [plugin, { root: '.' }],
-          [plugin, {
-            alias: {
-              '^@namespace/foo-(.+)': './packages/\\1',
-            },
-          }],
-        ],
-      };
-
-      it('should support replacing parts of a path', () => {
-        testWithImport(
-          '@namespace/foo-bar',
-          './packages/bar',
-          doubleAliasTransformerOpts,
-        );
-      });
-    });
-
     describe('missing packages warning', () => {
       const mockWarn = jest.fn();
       jest.mock('../src/log', () => ({