refactor(data): store city boundaries as .json behind a generated barrel

Bundlers do not treat .geojson as a module, so importing a boundary
statically failed to resolve. The content is JSON either way, and the
extension was the only thing standing in the way of the coverage page
reading a city outline.

The barrel matches the one the panorama indexes already use: generated
from what is on disk, rewritten after each city, so a build that has only
produced some of them still compiles.

scripts/build-city-boundaries.mjs

@@ -11,7 +11,7 @@
 // Output lands in src/data/boundaries/<code>.geojson and is meant to be edited
 // by hand afterwards if a city needs trimming. Re-running overwrites it.
 
-import { mkdirSync, writeFileSync } from 'node:fs';
+import { mkdirSync, readdirSync, writeFileSync } from 'node:fs';
 import * as turf from '@turf/turf';
 
 const NOMINATIM = 'https://nominatim.openstreetmap.org/search';
@@ -166,7 +166,7 @@ async function buildCity(code, config) {
   };
 
   mkdirSync(OUT_DIR, { recursive: true });
-  const path = `${OUT_DIR}/${code.toLowerCase()}.geojson`;
+  const path = `${OUT_DIR}/${code.toLowerCase()}.json`;
   writeFileSync(path, JSON.stringify(out, null, 1) + '\n');
   console.log(
     `  -> ${path}  ${out.properties.areaKm2} km2, ` +
@@ -174,9 +174,45 @@ async function buildCity(code, config) {
   );
 }
 
+/**
+ * Rewrite the barrel module that imports every boundary that exists.
+ *
+ * Same reason as the panorama indexes: static imports let the data be bundled
+ * with the server build, but a city that has not been generated yet would then
+ * be a hard build error. Generating the list from disk keeps a partial build
+ * usable.
+ * @returns {string[]} City codes now in the barrel.
+ */
+function writeBarrel() {
+  const entries = readdirSync(OUT_DIR)
+    .filter((name) => name.endsWith('.json') && name !== 'index.js')
+    .sort()
+    .map((name) => ({
+      code: name.replace(/\.json$/, '').toUpperCase(),
+      ident: name.replace(/\.json$/, ''),
+      file: name,
+    }));
+
+  const body =
+    '// Generated by scripts/build-city-boundaries.mjs. Do not edit by hand.\n' +
+    '//\n' +
+    '// Lists only the boundaries that have actually been built, so a partial\n' +
+    '// build still compiles.\n\n' +
+    entries.map((e) => `import ${e.ident} from './${e.file}';`).join('\n') +
+    '\n\nexport const CITY_BOUNDARIES = {\n' +
+    entries.map((e) => `  ${e.code}: ${e.ident},`).join('\n') +
+    '\n};\n';
+
+  writeFileSync(`${OUT_DIR}/index.js`, body);
+  return entries.map((e) => e.code);
+}
+
 const only = process.argv.slice(2);
 for (const [code, config] of Object.entries(CITIES)) {
   if (only.length && !only.includes(code)) continue;
   await buildCity(code, config);
+  // Rewritten after each city so an interrupted run leaves a consistent barrel.
+  writeBarrel();
 }
-console.log('\ndone');
+console.log(`\nbarrel: ${writeBarrel().join(', ')}`);
+console.log('done');

scripts/build-pano-index.mjs

@@ -155,7 +155,7 @@ function thinToGrid(points) {
 }
 
 async function buildCity(code, token) {
-  const boundaryPath = `${BOUNDARY_DIR}/${code.toLowerCase()}.geojson`;
+  const boundaryPath = `${BOUNDARY_DIR}/${code.toLowerCase()}.json`;
   if (!existsSync(boundaryPath)) {
     throw new Error(`${code}: missing ${boundaryPath} — run build-city-boundaries.mjs first`);
   }

src/data/boundaries/index.js

@@ -0,0 +1,18 @@
+// Generated by scripts/build-city-boundaries.mjs. Do not edit by hand.
+//
+// Lists only the boundaries that have actually been built, so a partial
+// build still compiles.
+
+import dh from './dh.json';
+import dl from './dl.json';
+import dn from './dn.json';
+import hn from './hn.json';
+import tphcm from './tphcm.json';
+
+export const CITY_BOUNDARIES = {
+  DH: dh,
+  DL: dl,
+  DN: dn,
+  HN: hn,
+  TPHCM: tphcm,
+};

tests/pano-index.test.js

@@ -43,7 +43,7 @@ describe('panorama index', () => {
 
   it.each(CODES)('%s panoramas sit inside the city boundary', (code) => {
     const boundary = JSON.parse(
-      readFileSync(`src/data/boundaries/${code.toLowerCase()}.geojson`, 'utf8')
+      readFileSync(`src/data/boundaries/${code.toLowerCase()}.json`, 'utf8')
     );
     // Sample rather than test every point: booleanPointInPolygon against a
     // detailed outline is slow, and a clipping bug would not hide in a sample.