build: generate topic sites during root build

Author: Song Mingxu

package.json

@@ -4,7 +4,8 @@
   "type": "module",
   "scripts": {
     "dev": "astro dev",
-    "build": "astro build && node scripts/copy-topic-sites.mjs",
+    "build:topics": "node scripts/build-topic-sites.mjs",
+    "build": "npm run build:topics && astro build && node scripts/copy-topic-sites.mjs",
     "preview": "astro preview",
     "check": "astro check"
   },

scripts/build-topic-sites.mjs

@@ -0,0 +1,36 @@
+import { existsSync } from "node:fs";
+import path from "node:path";
+import { spawnSync } from "node:child_process";
+
+import { findBuildableTopics } from "./topic-sites.mjs";
+
+const rootDir = process.cwd();
+const topics = findBuildableTopics(rootDir);
+
+for (const topic of topics) {
+  const hasNodeModules = existsSync(path.join(topic.dir, "node_modules"));
+  const hasLockfile = existsSync(path.join(topic.dir, "package-lock.json"));
+
+  if (!hasNodeModules) {
+    const installArgs = hasLockfile ? ["ci"] : ["install"];
+    const install = spawnSync("npm", installArgs, {
+      cwd: topic.dir,
+      stdio: "inherit",
+      shell: process.platform === "win32",
+    });
+
+    if (install.status !== 0) {
+      process.exit(install.status ?? 1);
+    }
+  }
+
+  const build = spawnSync("npm", ["run", "build"], {
+    cwd: topic.dir,
+    stdio: "inherit",
+    shell: process.platform === "win32",
+  });
+
+  if (build.status !== 0) {
+    process.exit(build.status ?? 1);
+  }
+}

scripts/copy-topic-sites.mjs

@@ -1,25 +1,20 @@
-import { cpSync, existsSync, mkdirSync, readdirSync } from "node:fs";
+import { cpSync, existsSync, mkdirSync } from "node:fs";
 import path from "node:path";
+import { findBuildableTopics, resolveTopicPublishSourceDir } from "./topic-sites.mjs";
 
 const rootDir = process.cwd();
-const topicsDir = path.join(rootDir, "topics");
 const distDir = path.join(rootDir, "dist");
 
-if (!existsSync(topicsDir) || !existsSync(distDir)) {
+if (!existsSync(distDir)) {
   process.exit(0);
 }
 
-for (const entry of readdirSync(topicsDir, { withFileTypes: true })) {
-  if (!entry.isDirectory()) continue;
-
-  const topicDir = path.join(topicsDir, entry.name);
-  const preferredSourceDir = path.join(topicDir, "site");
-  const fallbackSourceDir = path.join(topicDir, "dist");
-  const sourceDir = existsSync(preferredSourceDir) ? preferredSourceDir : fallbackSourceDir;
+for (const topic of findBuildableTopics(rootDir)) {
+  const sourceDir = resolveTopicPublishSourceDir(topic.dir);
 
   if (!existsSync(sourceDir)) continue;
 
-  const targetDir = path.join(distDir, "topics", entry.name, "site");
+  const targetDir = path.join(distDir, "topics", topic.name, "site");
   mkdirSync(path.dirname(targetDir), { recursive: true });
   cpSync(sourceDir, targetDir, { recursive: true });
 }

scripts/topic-sites.mjs

@@ -0,0 +1,46 @@
+import { existsSync, readFileSync, readdirSync } from "node:fs";
+import path from "node:path";
+
+export function findBuildableTopics(rootDir) {
+  const topicsDir = path.join(rootDir, "topics");
+
+  if (!existsSync(topicsDir)) {
+    return [];
+  }
+
+  return readdirSync(topicsDir, { withFileTypes: true })
+    .filter((entry) => entry.isDirectory())
+    .map((entry) => {
+      const topicDir = path.join(topicsDir, entry.name);
+      const packageJsonPath = path.join(topicDir, "package.json");
+
+      if (!existsSync(packageJsonPath)) {
+        return null;
+      }
+
+      const packageJson = JSON.parse(readFileSync(packageJsonPath, "utf8"));
+
+      return {
+        name: entry.name,
+        dir: topicDir,
+        packageJson,
+      };
+    })
+    .filter(Boolean)
+    .filter((topic) => topic.packageJson?.scripts?.build);
+}
+
+export function resolveTopicPublishSourceDir(topicDir) {
+  const distDir = path.join(topicDir, "dist");
+  const siteDir = path.join(topicDir, "site");
+
+  if (existsSync(distDir)) {
+    return distDir;
+  }
+
+  if (existsSync(siteDir)) {
+    return siteDir;
+  }
+
+  return null;
+}

scripts/topic-sites.test.mjs

@@ -0,0 +1,58 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import os from "node:os";
+import path from "node:path";
+import { mkdirSync, writeFileSync } from "node:fs";
+
+import {
+  findBuildableTopics,
+  resolveTopicPublishSourceDir,
+} from "./topic-sites.mjs";
+
+test("findBuildableTopics discovers topic apps with package.json", () => {
+  const rootDir = path.join(os.tmpdir(), `topic-sites-${Date.now()}-discover`);
+  const topicsDir = path.join(rootDir, "topics");
+
+  mkdirSync(path.join(topicsDir, "alpha"), { recursive: true });
+  mkdirSync(path.join(topicsDir, "beta"), { recursive: true });
+  mkdirSync(path.join(topicsDir, "docs-only"), { recursive: true });
+
+  writeFileSync(
+    path.join(topicsDir, "alpha", "package.json"),
+    JSON.stringify({ name: "alpha", scripts: { build: "vite build" } }),
+  );
+  writeFileSync(
+    path.join(topicsDir, "beta", "package.json"),
+    JSON.stringify({ name: "beta", scripts: { build: "vite build" } }),
+  );
+
+  const topics = findBuildableTopics(rootDir);
+
+  assert.deepEqual(
+    topics.map((topic) => topic.name),
+    ["alpha", "beta"],
+  );
+});
+
+test("resolveTopicPublishSourceDir prefers dist over stale site output", () => {
+  const topicDir = path.join(os.tmpdir(), `topic-sites-${Date.now()}-source`);
+
+  mkdirSync(path.join(topicDir, "site"), { recursive: true });
+  mkdirSync(path.join(topicDir, "dist"), { recursive: true });
+
+  assert.equal(
+    resolveTopicPublishSourceDir(topicDir),
+    path.join(topicDir, "dist"),
+  );
+});
+
+test("resolveTopicPublishSourceDir falls back to site when dist is missing", () => {
+  const topicDir = path.join(os.tmpdir(), `topic-sites-${Date.now()}-fallback`);
+
+  mkdirSync(path.join(topicDir, "site"), { recursive: true });
+
+  assert.equal(
+    resolveTopicPublishSourceDir(topicDir),
+    path.join(topicDir, "site"),
+  );
+});