build: generate the flatbuffers JavaScript bundle on demand

eslint.config.js

@@ -25,7 +25,7 @@ const config = [
       'prefer-template': 'error',
       'prefer-arrow-callback': 'error',
     },
-    ignores: ['node_modules/', 'build/', 'dist/', 'coverage/', 'features/support/fbresult_generated.js'],
+    ignores: ['node_modules/', 'build/', 'dist/', 'coverage/', 'features/generated/**'],
   },
 ];
 

features/step_definitions/distance_matrix.js

@@ -2,7 +2,7 @@
 import util from 'util';
 
 import flatbuffers from 'flatbuffers';
-import { osrm } from '../support/fbresult_generated.js';
+import { osrm } from '../support/fbresult.js';
 const FBResult = osrm.engine.api.fbresult.FBResult;
 import { When } from '@cucumber/cucumber';
 

features/step_definitions/nearest.js

@@ -2,7 +2,7 @@
 import util from 'util';
 
 import flatbuffers from 'flatbuffers';
-import { osrm } from '../support/fbresult_generated.js';
+import { osrm } from '../support/fbresult.js';
 const FBResult = osrm.engine.api.fbresult.FBResult;   
 import assert from 'node:assert';
 import { When } from '@cucumber/cucumber';

features/support/fbresult.js

@@ -0,0 +1,28 @@
+// Loads the flatbuffers JavaScript bundle used to decode `format=flatbuffers`
+// responses, generating it first from include/engine/api/flatbuffers/*.fbs.
+//
+// The bundle is not committed: a stale copy silently decodes the old field
+// layout, so it is rebuilt whenever the schemas change. The script returns
+// immediately when the bundle is already up to date.
+import { execFileSync } from 'node:child_process';
+import path from 'node:path';
+import { fileURLToPath, pathToFileURL } from 'node:url';
+
+const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '../..');
+
+try {
+  execFileSync('bash', [path.join(root, 'scripts/regenerate_fbresult_js.sh')], {
+    cwd: root,
+    // Keep stdout quiet so it does not interleave with cucumber's formatter,
+    // but let errors (such as "no flatc found") through.
+    stdio: ['ignore', 'ignore', 'inherit'],
+  });
+} catch {
+  throw new Error(
+    'Failed to generate features/generated/fbresult.js from the flatbuffers ' +
+      'schemas (see the message above). Run `npm run regenerate-fbresult` for details.'
+  );
+}
+
+const bundle = pathToFileURL(path.join(root, 'features/generated/fbresult.js')).href;
+export const { osrm } = await import(bundle);