ci(deploy): detect changes caused by dependency versions

TL;DR: When comparing compiled scripts, we'll compile them in a
child process and make sure that the dependencies are installed
according to the lock file.

.github/actions/setup/action.yml

@@ -5,7 +5,7 @@ inputs:
   node-version:
     description: Node version to install, defaults to v16
     required: false
-    default: '16'
+    default: '18'
 runs:
   using: composite
   steps:

build/build.ts

@@ -3,5 +3,8 @@ import { getVersionForToday } from './versions';
 
 // Don't use await at the top level, this is incompatible with node and
 // CommonJS modules.
-buildUserscripts(getVersionForToday()).
-    catch(console.error);
+buildUserscripts(getVersionForToday())
+    .catch((err) => {
+        console.error(err);
+        throw err;
+    });

build/check-scripts-unchanged.ts

@@ -1,5 +1,6 @@
 import fs from 'node:fs/promises';
 
+import { buildUserscript } from './rollup';
 import { getPreviousReleaseVersion, userscriptHasChanged } from './versions';
 
 if (!process.env.GITHUB_ACTIONS) {
@@ -22,6 +23,9 @@ async function checkUserscriptsChanged(): Promise<void> {
 
         // Check against the main branch.
         if (await userscriptHasChanged(scriptName, 'main')) {
+            // Build it again into the dist repo so that the changes can be
+            // displayed.
+            await buildUserscript(scriptName, previousVersion, distRepo);
             throw new Error(`Userscript ${scriptName} would be changed`);
         }
     }

build/versions.ts

@@ -1,10 +1,10 @@
+import { exec } from 'node:child_process';
 import fs from 'node:fs/promises';
 import path from 'node:path';
+import { promisify } from 'node:util';
 
 import simpleGit from 'simple-git';
 
-import { buildUserscript } from './rollup';
-
 export function getVersionForToday(): string {
     const today = new Date();
     return `${today.getUTCFullYear()}.${today.getUTCMonth() + 1}.${today.getUTCDate()}`;
@@ -58,7 +58,26 @@ export async function getPreviousReleaseVersion(userscriptName: string, buildDir
 
 async function buildTempUserscript(scriptName: string): Promise<string> {
     const outputDir = await fs.mkdtemp(scriptName);
-    await buildUserscript(scriptName, '0.0.0', outputDir);
+
+    // Need to run this in its own process because we may need to change the
+    // versions of dependencies and ensure the node process uses the correct
+    // version. We also can't just change the `build.ts` script to accept
+    // arguments because we may need to compare to a version in which the script
+    // hadn't been changed yet.
+    const builderSource = `
+        import { buildUserscript } from "build/rollup";
+        buildUserscript("${scriptName}", "0.0.0", "${path.resolve(outputDir)}")
+            .catch((err) => {
+                console.error(err);
+                throw err;
+            });
+    `;
+    await fs.writeFile('isolatedBuilder.ts', builderSource);
+    const command = 'npm i --no-audit --production=false && npx ts-node -r tsconfig-paths/register isolatedBuilder.ts';
+    const { stderr, stdout } = await promisify(exec)(command);
+    if (stderr) console.error(stderr);
+    if (stdout) console.log(stdout);
+
     const content = fs.readFile(path.join(outputDir, `${scriptName}.user.js`), 'utf8');
     await fs.rm(outputDir, { recursive: true });
     return content;
@@ -68,7 +87,9 @@ export async function userscriptHasChanged(scriptName: string, compareToRef: str
     // We'll check whether the userscript has changed by building both the
     // latest code as well as the code at `baseRef`, then diffing them.
     // If there's a diff, we assume it needs a new release.
-    const currentVersion = await buildTempUserscript(scriptName);
+
+    // Build previous version before current version so that the current
+    // dependency versions are installed after everything is finished.
 
     // Temporarily check out the base ref
     const repo = simpleGit();
@@ -80,5 +101,7 @@ export async function userscriptHasChanged(scriptName: string, compareToRef: str
         await repo.checkout('-');
     }
 
+    const currentVersion = await buildTempUserscript(scriptName);
+
     return currentVersion !== previousVersion;
 }