fix: dedupe Solid packages in production builds

.changeset/dedupe-solid-in-builds.md

@@ -0,0 +1,5 @@
+---
+'@solidjs/vite-plugin': patch
+---
+
+Production builds now dedupe `solid-js`, `@solidjs/web` and `@solidjs/signals` the same way dev does. A dependency with its own nested copy of Solid no longer adds a second runtime to the bundle, which broke context lookups (#112).

src/dedupe.test.ts

@@ -0,0 +1,66 @@
+import { mkdtemp, mkdir, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import { build, type Rolldown } from 'vite';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import solidPlugin from './index.js';
+
+let root: string;
+
+async function writePackage(dir: string, pkg: Record<string, unknown>, files: Record<string, string>) {
+  await mkdir(dir, { recursive: true });
+  await writeFile(path.join(dir, 'package.json'), JSON.stringify(pkg));
+  for (const [name, code] of Object.entries(files)) {
+    await writeFile(path.join(dir, name), code);
+  }
+}
+
+beforeAll(async () => {
+  root = await mkdtemp(path.join(tmpdir(), 'solid-dedupe-'));
+  const fakeSolid = (copy: string) => [
+    { name: 'solid-js', version: '2.0.0', type: 'module', exports: { '.': './index.js' } },
+    { 'index.js': `export const copy = ${JSON.stringify(copy)};\n` },
+  ] as const;
+  await writePackage(path.join(root, 'node_modules/solid-js'), ...fakeSolid('root'));
+  // A dependency that ships its own nested copy of solid-js.
+  const lib = path.join(root, 'node_modules/lib');
+  await writePackage(
+    lib,
+    { name: 'lib', version: '1.0.0', type: 'module', exports: { '.': './index.js' } },
+    { 'index.js': "export { copy as libCopy } from 'solid-js';\n" },
+  );
+  await writePackage(path.join(lib, 'node_modules/solid-js'), ...fakeSolid('nested'));
+  await writeFile(path.join(root, 'package.json'), JSON.stringify({ name: 'app', type: 'module' }));
+  await writeFile(
+    path.join(root, 'entry.js'),
+    "import { copy } from 'solid-js';\nimport { libCopy } from 'lib';\nexport const copies = [copy, libCopy];\n",
+  );
+});
+
+afterAll(async () => {
+  await rm(root, { recursive: true, force: true });
+});
+
+describe('resolve.dedupe', () => {
+  // #112: dev deduped solid-js, but production builds bundled the nested copy too.
+  it('bundles a single solid-js copy in production builds', async () => {
+    const result = (await build({
+      root,
+      configFile: false,
+      logLevel: 'silent',
+      plugins: [solidPlugin()],
+      build: {
+        write: false,
+        minify: false,
+        rolldownOptions: { input: path.join(root, 'entry.js'), preserveEntrySignatures: 'strict' },
+      },
+    })) as Rolldown.RolldownOutput | Rolldown.RolldownOutput[];
+    const output = Array.isArray(result) ? result[0] : result;
+    const code = output.output
+      .filter((chunk): chunk is Rolldown.OutputChunk => chunk.type === 'chunk')
+      .map((chunk) => chunk.code)
+      .join('\n');
+    expect(code).toContain('"root"');
+    expect(code).not.toContain('"nested"');
+  });
+});

src/index.ts

@@ -1521,10 +1521,16 @@ export default function solidPlugin(options: Partial<Options> = {}): Plugin[] {
       // added to `optimizeDeps.include`: the optimizer already reaches
       // signals through `solid-js`, and an include entry that doesn't
       // resolve from the root logs a warning on every start.
-      const dedupe =
-        replaceDev && findPackageDir('@solidjs/signals', path.resolve(projectRoot || process.cwd()))
-          ? [...nestedDeps, '@solidjs/signals']
-          : nestedDeps;
+      //
+      // Dedupe applies to builds as well as dev. A dependency that ships its
+      // own nested copy of `solid-js` would otherwise put a second runtime
+      // in the production bundle, with its own owner tree and contexts. #112
+      // Each package is only listed when the root can resolve it, for the
+      // reason given above for `@solidjs/signals`.
+      const dedupeRoot = path.resolve(projectRoot || process.cwd());
+      const dedupe = ['solid-js', '@solidjs/web', '@solidjs/signals'].filter((name) =>
+        findPackageDir(name, dedupeRoot),
+      );
 
       const userTest = (userConfig as any).test ?? {};
       const test = {} as any;