build: ship each bundled data pack once

loadBundledJson's callers passed a literal JSON import as a Node fallback,
which made the production build emit a JavaScript copy of every pack beside
the JSON the browser fetches. The loader now reads file: URLs itself under
Node (through process.getBuiltinModule, synchronously, as promptly as the
cached import it replaces), and the callers pass only the URL. On a Node too
old to provide getBuiltinModule it says that Node 24.14 or newer is needed.
dist/ drops from 54 MB to 42 MB. A test keeps app code from importing a pack
as a module.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/data/adminBoundaries.js

@@ -58,30 +58,18 @@ export function normalizeAdminName(value) {
 const PACKS = {
   countries: {
     url: new URL('./local_data/natural_earth/countries.json', import.meta.url),
-    importJson: () =>
-      import('./local_data/natural_earth/countries.json', {
-        with: { type: 'json' },
-      }),
   },
   admin1: {
     url: new URL(
       './local_data/natural_earth/states_provinces.json',
       import.meta.url,
     ),
-    importJson: () =>
-      import('./local_data/natural_earth/states_provinces.json', {
-        with: { type: 'json' },
-      }),
   },
   counties: {
     url: new URL(
       './local_data/us_census_counties/counties.json',
       import.meta.url,
     ),
-    importJson: () =>
-      import('./local_data/us_census_counties/counties.json', {
-        with: { type: 'json' },
-      }),
   },
 };
 
@@ -297,7 +285,7 @@ function addKey(index, key, entry, tier) {
 
 const loadAdmin1 = createRetryableLoader(async () => {
   packLoads.admin1 += 1;
-  const pack = await loadBundledJson(PACKS.admin1.url, PACKS.admin1.importJson);
+  const pack = await loadBundledJson(PACKS.admin1.url);
   const decimals = pack.meta?.decimals ?? 3;
   const index = new Map();
   for (const feature of pack.features || []) {
@@ -323,10 +311,7 @@ const loadAdmin1 = createRetryableLoader(async () => {
 
 const loadCounties = createRetryableLoader(async () => {
   packLoads.counties += 1;
-  const pack = await loadBundledJson(
-    PACKS.counties.url,
-    PACKS.counties.importJson,
-  );
+  const pack = await loadBundledJson(PACKS.counties.url);
   const decimals = pack.meta?.decimals ?? 4;
   const byFull = new Map();
   const byName = new Map();
@@ -348,10 +333,7 @@ const loadCounties = createRetryableLoader(async () => {
 
 const loadCountries = createRetryableLoader(async () => {
   packLoads.countries += 1;
-  const pack = await loadBundledJson(
-    PACKS.countries.url,
-    PACKS.countries.importJson,
-  );
+  const pack = await loadBundledJson(PACKS.countries.url);
   const index = new Map();
   for (const feature of pack.features || []) {
     const entry = {

src/data/bundledJson.js

@@ -4,24 +4,38 @@
  * The browser fetches the file from `url` — a `new URL('./….json',
  * import.meta.url)` written in the calling module, which Vite serves as-is in
  * dev and emits as an asset in the production build. Under Node (node:test)
- * that URL is a `file:` URL, which `fetch` cannot read, so the caller's
- * JSON-attributed import runs instead.
+ * that URL is a `file:` URL, which `fetch` cannot read, so the file is read
+ * from disk instead.
  *
- * The attributed import cannot serve the browser: the Vite dev server answers
- * it with a JavaScript module, which the browser rejects for a JSON import.
+ * Nothing here imports the JSON as a module. A JSON-attributed import cannot
+ * serve the browser (the Vite dev server answers it with a JavaScript module,
+ * which the browser rejects), and a literal `import('./….json')` makes the
+ * production build emit a JavaScript copy of every pack that the browser
+ * never loads.
  *
  * @module data/bundledJson
  */
 
 /**
  * @param {URL} url - Resolved against the calling module's `import.meta.url`.
- * @param {() => Promise<{default: any}>} importJson - The caller's literal
- *   `import('./….json', { with: { type: 'json' } })`, used only under Node.
+ * @param {{signal?: AbortSignal}} [options]
  * @returns {Promise<any>} The parsed JSON.
  */
-export async function loadBundledJson(url, importJson, { signal } = {}) {
-  if (url.protocol === 'file:') return (await importJson()).default;
+export async function loadBundledJson(url, { signal } = {}) {
   signal?.throwIfAborted();
+  if (url.protocol === 'file:') {
+    // Node's built-in, reached without an import, so the browser build never
+    // bundles or rewrites it; only Node, reading `file:` URLs, gets here. The
+    // read is synchronous so the result settles as promptly as the cached
+    // module import it replaces; callers already memoize each pack.
+    const getBuiltinModule = globalThis.process?.getBuiltinModule;
+    if (typeof getBuiltinModule !== 'function')
+      throw new Error(
+        `God's Eye View needs Node 24.14 or newer to read ${url.pathname.split('/').pop()} (running ${globalThis.process?.version ?? 'an unknown runtime'})`,
+      );
+    const { readFileSync } = getBuiltinModule('node:fs');
+    return JSON.parse(readFileSync(url, 'utf8'));
+  }
   const response = await fetch(url, { signal });
   if (!response.ok) {
     throw new Error(`HTTP ${response.status} for ${url.pathname}`);

src/data/bundledJson.test.mjs

@@ -2,13 +2,14 @@ import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import { loadBundledJson } from './bundledJson.js';
 
-const MARINE = new URL('./local_data/natural_earth/marine.json', import.meta.url);
-const importMarine = () =>
-  import('./local_data/natural_earth/marine.json', { with: { type: 'json' } });
+const MARINE = new URL(
+  './local_data/natural_earth/marine.json',
+  import.meta.url,
+);
 
-test('bundled JSON: a file URL uses the JSON import under Node', async (t) => {
+test('bundled JSON: a file URL is read from disk under Node', async (t) => {
   const fetchMock = t.mock.method(globalThis, 'fetch');
-  const pack = await loadBundledJson(MARINE, importMarine);
+  const pack = await loadBundledJson(MARINE);
   assert.ok(pack.features.some((ft) => ft.name === 'Gulf of Mexico'));
   assert.equal(fetchMock.mock.callCount(), 0);
 });
@@ -21,16 +22,62 @@ test('bundled JSON: a served URL is fetched as plain JSON', async (t) => {
       headers: { 'content-type': 'application/json' },
     });
   });
-  const url = new URL('http://localhost/src/data/local_data/natural_earth/marine.json');
-  const importJson = () => assert.fail('the browser path must not import JSON');
-  assert.deepEqual(await loadBundledJson(url, importJson), { features: [] });
+  const url = new URL(
+    'http://localhost/src/data/local_data/natural_earth/marine.json',
+  );
+  assert.deepEqual(await loadBundledJson(url), { features: [] });
   assert.deepEqual(requests, [url.href]);
 });
 
 test('bundled JSON: an HTTP error rejects so the retryable loader can retry', async (t) => {
-  t.mock.method(globalThis, 'fetch', async () => new Response('', { status: 404 }));
+  t.mock.method(
+    globalThis,
+    'fetch',
+    async () => new Response('', { status: 404 }),
+  );
   await assert.rejects(
-    loadBundledJson(new URL('http://localhost/missing.json'), importMarine),
+    loadBundledJson(new URL('http://localhost/missing.json')),
     /HTTP 404/,
   );
 });
+
+test('bundled JSON: an aborted load rejects before reading', async () => {
+  const controller = new AbortController();
+  controller.abort();
+  await assert.rejects(loadBundledJson(MARINE, { signal: controller.signal }), {
+    name: 'AbortError',
+  });
+});
+
+test('bundled JSON: no data pack is imported as a module', async () => {
+  // A literal JSON import in app code makes the production build emit a
+  // JavaScript copy of the pack beside the fetched JSON, which the browser
+  // never loads. Tests are not bundled, so they may still import JSON.
+  const { spawnSync } = await import('node:child_process');
+  const result = spawnSync(
+    'git',
+    [
+      'grep',
+      '-nE',
+      String.raw`import\(\s*['"][^'"]*local_data/[^'"]*\.json`,
+      '--',
+      'src',
+      ':!*.test.mjs',
+    ],
+    { cwd: new URL('../../', import.meta.url), encoding: 'utf8' },
+  );
+  // git grep exits 1 when nothing matches.
+  assert.equal(result.status, 1, result.stdout);
+});
+
+test('bundled JSON: an older Node says which version is needed', async (t) => {
+  // Node before 20.16 / 22.3 has no process.getBuiltinModule.
+  const original = process.getBuiltinModule;
+  t.after(() => {
+    process.getBuiltinModule = original;
+  });
+  process.getBuiltinModule = undefined;
+  await assert.rejects(loadBundledJson(MARINE), {
+    message: /needs Node 24\.14 or newer to read marine\.json/,
+  });
+});

src/data/militaryNames.js

@@ -14,10 +14,6 @@ export function createMilitaryNamesLoader({
   loadPack = (signal) =>
     loadBundledJson(
       new URL('./local_data/osm_military_names/names.json', import.meta.url),
-      () =>
-        import('./local_data/osm_military_names/names.json', {
-          with: { type: 'json' },
-        }),
       { signal },
     ),
   timeoutMs = MILITARY_NAMES_TIMEOUT_MS,

src/data/naturalEarthRegions.js

@@ -124,17 +124,9 @@ let _entries = null;
 const PACKS = {
   regions: {
     url: new URL('./local_data/natural_earth/regions.json', import.meta.url),
-    importJson: () =>
-      import('./local_data/natural_earth/regions.json', {
-        with: { type: 'json' },
-      }),
   },
   marine: {
     url: new URL('./local_data/natural_earth/marine.json', import.meta.url),
-    importJson: () =>
-      import('./local_data/natural_earth/marine.json', {
-        with: { type: 'json' },
-      }),
   },
 };
 
@@ -178,8 +170,8 @@ function buildEntries(pack, kind) {
  */
 const loadIndex = createRetryableLoader(async () => {
   const [regions, marine] = await Promise.all([
-    loadBundledJson(PACKS.regions.url, PACKS.regions.importJson),
-    loadBundledJson(PACKS.marine.url, PACKS.marine.importJson),
+    loadBundledJson(PACKS.regions.url),
+    loadBundledJson(PACKS.marine.url),
   ]);
   _entries = [
     ...buildEntries(regions, 'natural'),

src/data/neighborhoodPolygons.js

@@ -22,10 +22,6 @@ const CITY_FILES = [
       './local_data/neighborhoods/san-francisco.json',
       import.meta.url,
     ),
-    importJson: () =>
-      import('./local_data/neighborhoods/san-francisco.json', {
-        with: { type: 'json' },
-      }),
   },
 ];
 
@@ -112,7 +108,7 @@ function cityLoader(city) {
   let loader = _cityLoaders.get(city.id);
   if (!loader) {
     loader = createRetryableLoader(async () => {
-      const fc = await loadBundledJson(city.url, city.importJson);
+      const fc = await loadBundledJson(city.url);
       return Array.isArray(fc.features) ? fc.features : [];
     });
     _cityLoaders.set(city.id, loader);