sagas/mpy: Use legacy __main__ on old firmware.

Author: laurensvalk

src/hub/reducers.test.ts

@@ -58,6 +58,7 @@ test('initial state', () => {
           "runtime": "hub.runtime.disconnected",
           "selectedSlot": 0,
           "useLegacyDownload": false,
+          "useLegacyMainModule": false,
           "useLegacyStartUserProgram": false,
           "useLegacyStdio": false,
         }
@@ -544,3 +545,23 @@ describe('useLegacyStartUserProgram', () => {
         ).toBeFalsy();
     });
 });
+
+describe('useLegacyMainModule', () => {
+    test('Pybricks Profile < v1.5.0', () => {
+        expect(
+            reducers(
+                { useLegacyMainModule: false } as State,
+                bleDIServiceDidReceiveSoftwareRevision('1.4.0'),
+            ).useLegacyMainModule,
+        ).toBeTruthy();
+    });
+
+    test('Pybricks Profile >= v1.5.0', () => {
+        expect(
+            reducers(
+                { useLegacyMainModule: true } as State,
+                bleDIServiceDidReceiveSoftwareRevision('1.5.0'),
+            ).useLegacyMainModule,
+        ).toBeFalsy();
+    });
+});

src/hub/reducers.ts

@@ -381,6 +381,18 @@ const useLegacyStartUserProgram: Reducer<boolean> = (state = false, action) => {
     return state;
 };
 
+/**
+ * When true, use the legacy `__main__` module name instead of the actual file name.
+ */
+const useLegacyMainModule: Reducer<boolean> = (state = false, action) => {
+    if (bleDIServiceDidReceiveSoftwareRevision.matches(action)) {
+        // Behavior changed starting with Pybricks Profile v1.5.0.
+        return !semver.satisfies(action.version, '^1.5.0');
+    }
+
+    return state;
+};
+
 /*
  * Returns number of available slots or 0 for slots not supported.
  */
@@ -418,6 +430,7 @@ export default combineReducers({
     useLegacyDownload,
     useLegacyStdio,
     useLegacyStartUserProgram,
+    useLegacyMainModule,
     numOfSlots,
     selectedSlot,
 });

src/hub/sagas.ts

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2020-2024 The Pybricks Authors
+// Copyright (c) 2020-2026 The Pybricks Authors
 
 import {
     SagaGenerator,
@@ -202,7 +202,11 @@ function* handleDownloadAndRun(action: ReturnType<typeof downloadAndRun>): Gener
             (s: RootState) => s.hub.maxUserProgramSize,
         );
 
-        yield* put(mpyCompileMulti6());
+        const useLegacyMainModule = yield* select(
+            (s: RootState) => s.hub.useLegacyMainModule,
+        );
+
+        yield* put(mpyCompileMulti6(useLegacyMainModule));
 
         const { didCompile, didFailToCompile } = yield* race({
             didCompile: take(mpyDidCompileMulti6),

src/mpy/actions.ts

@@ -23,8 +23,13 @@ export const didFailToCompile = createAction((err: string[]) => ({
     err,
 }));
 
-export const mpyCompileMulti6 = createAction(() => ({
+/**
+ * Request to compile multiple Python files into multi-mpy6 format.
+ * @param useLegacyMainModule Whether to use the legacy `__main__` module name (changed in protocol v1.5.0).
+ */
+export const mpyCompileMulti6 = createAction((useLegacyMainModule: boolean) => ({
     type: 'mpy.action.compileMulti6',
+    useLegacyMainModule,
 }));
 
 export const mpyDidCompileMulti6 = createAction((file: Blob) => ({

src/mpy/sagas.ts

@@ -104,10 +104,10 @@ function* handleCompile(action: ReturnType<typeof compile>): Generator {
 /**
  * Compiles code into the Pybricks multi-mpy6 file format.
  *
- * This includes a __main__ module which is the file currently open in the
- * editor and any imported modules that can be found in the user file system.
+ * This includes the file currently open in the editor and any imported modules
+ * that can be found in the user file system.
  */
-function* handleCompileMulti6(): Generator {
+function* handleCompileMulti6(action: ReturnType<typeof mpyCompileMulti6>): Generator {
     // REVISIT: should we be getting the active file here or have it as an
     // action parameter?
 
@@ -129,7 +129,9 @@ function* handleCompileMulti6(): Generator {
     }
 
     const mainPy = yield* editorGetValue();
-    const mainPyPath = metadata.path ?? '__main__.py';
+    const mainPyPath = action.useLegacyMainModule
+        ? '__main__.py'
+        : metadata.path ?? '__main__.py';
     const mainPyName = mainPyPath.replace(/\.[^.]+$/, '');
 
     const pyFiles = new Map<string, FileContents>([