fix(mobile): prevent crash when generated/openapi has unexpected files (#32599)

(cherry picked from commit 4f38929bdaaa88d48429ac642abf9ec292e3ca82)

mobile/mise.toml

@@ -139,6 +139,7 @@ depends = ["//:open-api-dart"]
 run = [
   # This receives passed `--enforce-lockfile` args
   "flutter pub get",
+  { task = "install:build-runner-patch" },
   { task = "install:ios" },
 ]
 
@@ -198,6 +199,11 @@ fi
 cd ios && pod install
 '''
 
+[tasks."install:build-runner-patch"]
+description = "Patch build_runner to prevent crashes when sources are deleted"
+hide = true
+run = "node ./scripts/build_runner_patch.mjs"
+
 [tasks."analyze:dart"]
 description = "Run Dart analysis"
 hide = true

mobile/scripts/build_runner_patch.mjs

@@ -0,0 +1,20 @@
+// Prevents build_runner crashing when a source file is deleted from a path dependency, which commonly occurs to `generated/openapi` on branch switch
+//
+// Fixed upstream in 2.15.3 (https://github.com/dart-lang/build/pull/5022), but we can't take that dependency due to Dart analyzer being locked
+import { readFileSync, writeFileSync } from 'node:fs';
+
+const packageConfig = new URL('../.dart_tool/package_config.json', import.meta.url);
+
+const config = JSON.parse(readFileSync(packageConfig, 'utf8'));
+const buildRunner = new URL(config.packages.find(({ name }) => name === 'build_runner').rootUri);
+
+const file = new URL(`${buildRunner}/lib/src/build_plan/build_plan.dart`);
+
+const buggy = 'for (final id in deletedOutputs) {';
+const fixed = 'for (final id in deletedOutputs.difference(buildInputs.deletedSources.build().asSet())) {';
+
+const source = readFileSync(file, 'utf8');
+if (source.includes(buggy)) {
+  writeFileSync(file, source.replace(buggy, fixed));
+  console.log('build_runner patch: stopped deleting removed sources from path dependencies');
+}