Add resolutionPlatforms for better React Native support

Author: Sverre Johansen

src/compiler/commandLineParser.ts

@@ -415,7 +415,17 @@ namespace ts {
             category: Diagnostics.Module_Resolution_Options,
             description: Diagnostics.Do_not_resolve_the_real_path_of_symlinks,
         },
-
+        {
+            name: "resolutionPlatforms",
+            type: "list",
+            element: {
+                name: "types",
+                type: "string"
+            },
+            showInSimplifiedHelpView: true,
+            category: Diagnostics.Module_Resolution_Options,
+            description: Diagnostics.List_of_platform_extensions_to_fallback_on
+         },
         // Source Maps
         {
             name: "sourceRoot",

src/compiler/diagnosticMessages.json

@@ -3889,6 +3889,10 @@
         "category": "Message",
         "code": 90029
     },
+    "List of platform extensions to fallback on": {
+        "category": "Message",
+        "code": 910044
+    },
     "Convert function to an ES2015 class": {
         "category": "Message",
         "code": 95001

src/compiler/moduleNameResolver.ts

@@ -925,22 +925,46 @@ namespace ts {
     }
 
     /** Return the file if it exists. */
-    function tryFile(fileName: string, failedLookupLocations: Push<string>, onlyRecordFailures: boolean, state: ModuleResolutionState): string | undefined {
-        if (!onlyRecordFailures) {
-            if (state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
+    function tryFile(file: string, failedLookupLocations: Push<string>, onlyRecordFailures: boolean, state: ModuleResolutionState): string | undefined {
+
+        if (state.compilerOptions.resolutionPlatforms){
+            for(let platform of state.compilerOptions.resolutionPlatforms) {
+                let result = tryFileInner(platform);
+                if (result) {
+                    return result;
                 }
-                return fileName;
             }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.File_0_does_not_exist, fileName);
+        }
+
+        return tryFileInner(null);
+
+        function tryFileInner(platform: string): string | undefined {
+            
+            let fileName = file;
+            if (platform) {
+              let lastDot = file.lastIndexOf('.');
+              if (lastDot === -1) {
+                  return undefined;
+              }
+              fileName = file.slice(0, lastDot + 1) + platform + file.slice(lastDot);
+            }
+
+            if (!onlyRecordFailures) {
+                if (state.host.fileExists(fileName)) {
+                    if (state.traceEnabled) {
+                        trace(state.host, Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
+                    }
+                    return fileName;
+                }
+                else {
+                    if (state.traceEnabled) {
+                        trace(state.host, Diagnostics.File_0_does_not_exist, fileName);
+                    }
                 }
             }
+            failedLookupLocations.push(fileName);
+            return undefined;
         }
-        failedLookupLocations.push(fileName);
-        return undefined;
     }
 
     function loadNodeModuleFromDirectory(extensions: Extensions, candidate: string, failedLookupLocations: Push<string>, onlyRecordFailures: boolean, state: ModuleResolutionState, considerPackageJson = true) {

src/compiler/types.ts

@@ -4019,6 +4019,7 @@ namespace ts {
         reactNamespace?: string;
         jsxFactory?: string;
         removeComments?: boolean;
+        resolutionPlatforms?: string[]; // Use react-native lookup logic for these platforms
         rootDir?: string;
         rootDirs?: string[];
         skipLibCheck?: boolean;