[cli] Switch to npm and add more context to install errors during Builder import (#8545)

Before:

<img width="1012" alt="Screen Shot 2022-09-09 at 7 03 01 PM" src="https://user-images.githubusercontent.com/71256/189464732-8cf6398a-9432-423b-8509-a52bd714333e.png">

After:

<img width="579" alt="Screen Shot 2022-09-12 at 12 27 31 PM" src="https://user-images.githubusercontent.com/71256/189739091-86399428-d9b8-4d03-b0e6-7d27a1037bce.png">

This is a precursor to https://github.com/vercel/vercel/pull/8485, since the last remaining test failure there is related to specialized messaging we had for these same cases.

packages/cli/src/util/build/import-builders.ts

@@ -1,3 +1,5 @@
+import { URL } from 'url';
+import plural from 'pluralize';
 import npa from 'npm-package-arg';
 import { satisfies } from 'semver';
 import { dirname, join } from 'path';
@@ -13,6 +15,9 @@ import { VERCEL_DIR } from '../projects/link';
 import { Output } from '../output';
 import readJSONFile from '../read-json-file';
 import { CantParseJSONFile } from '../errors-ts';
+import { errorToString, isErrnoException, isError } from '../is-error';
+import cmd from '../output/cmd';
+import code from '../output/code';
 
 export interface BuilderWithPkg {
   path: string;
@@ -201,15 +206,54 @@ async function installBuilders(
     if (err.code !== 'EEXIST') throw err;
   }
 
-  output.debug(`Installing Builders: ${Array.from(buildersToAdd).join(', ')}`);
-  await spawnAsync('yarn', ['add', '@vercel/build-utils', ...buildersToAdd], {
-    cwd: buildersDir,
-  });
+  output.log(
+    `Installing ${plural('Builder', buildersToAdd.size)}: ${Array.from(
+      buildersToAdd
+    ).join(', ')}`
+  );
+  try {
+    await spawnAsync(
+      'npm',
+      ['install', '@vercel/build-utils', ...buildersToAdd],
+      {
+        cwd: buildersDir,
+        stdio: 'pipe',
+      }
+    );
+  } catch (err: unknown) {
+    if (isError(err)) {
+      (err as any).link =
+        'https://vercel.link/builder-dependencies-install-failed';
+      if (isErrnoException(err) && err.code === 'ENOENT') {
+        // `npm` is not installed
+        err.message = `Please install ${cmd('npm')} before continuing`;
+      } else {
+        const message = errorToString(err);
+        const notFound = /GET (.*) - Not found/.exec(message);
+        if (notFound) {
+          const url = new URL(notFound[1]);
+          const packageName = decodeURIComponent(url.pathname.slice(1));
+          err.message = `The package ${code(
+            packageName
+          )} is not published on the npm registry`;
+        }
+      }
+    }
+    throw err;
+  }
 
   // Symlink `@now/build-utils` -> `@vercel/build-utils` to support legacy Builders
   const nowScopePath = join(buildersDir, 'node_modules/@now');
   await mkdirp(nowScopePath);
-  await symlink('../@vercel/build-utils', join(nowScopePath, 'build-utils'));
+
+  try {
+    await symlink('../@vercel/build-utils', join(nowScopePath, 'build-utils'));
+  } catch (err: unknown) {
+    if (!isErrnoException(err) || err.code !== 'EEXIST') {
+      // Throw unless the error is due to the symlink already existing
+      throw err;
+    }
+  }
 
   // Cross-reference any builderSpecs from the saved `package.json` file,
   // in case they were installed from a URL

packages/cli/test/unit/util/build/import-builders.test.ts

@@ -37,20 +37,56 @@ describe('importBuilders()', () => {
     const cwd = await getWriteableDirectory();
     try {
       const spec = 'vercel-deno@2.0.1';
-      const specs = new Set([spec]);
+      const tarballSpec = 'https://test2020-h5hdll5dz-tootallnate.vercel.app';
+      const specs = new Set([spec, tarballSpec]);
       const builders = await importBuilders(specs, cwd, client.output);
-      expect(builders.size).toEqual(1);
+      expect(builders.size).toEqual(2);
       expect(builders.get(spec)?.pkg.name).toEqual('vercel-deno');
       expect(builders.get(spec)?.pkg.version).toEqual('2.0.1');
       expect(builders.get(spec)?.pkgPath).toEqual(
         join(cwd, '.vercel/builders/node_modules/vercel-deno/package.json')
       );
-      expect(typeof builders.get(spec)?.builder.build).toEqual('function');
+      expect(builders.get(tarballSpec)?.pkg.name).toEqual('vercel-bash');
+      expect(builders.get(tarballSpec)?.pkg.version).toEqual('4.1.0');
+      expect(builders.get(tarballSpec)?.pkgPath).toEqual(
+        join(cwd, '.vercel/builders/node_modules/vercel-bash/package.json')
+      );
+      expect(typeof builders.get(tarballSpec)?.builder.build).toEqual(
+        'function'
+      );
+      await expect(client.stderr).toOutput(
+        '> Installing Builders: vercel-deno@2.0.1, https://test2020-h5hdll5dz-tootallnate.vercel.app'
+      );
     } finally {
       await remove(cwd);
     }
   });
 
+  it('should throw when importing a Builder that is not on npm registry', async () => {
+    let err: Error | undefined;
+    const cwd = await getWriteableDirectory();
+    try {
+      const spec = '@vercel/does-not-exist@0.0.1';
+      const specs = new Set([spec]);
+      await importBuilders(specs, cwd, client.output);
+    } catch (_err) {
+      err = _err;
+    } finally {
+      await remove(cwd);
+    }
+
+    if (!err) {
+      throw new Error('Expected `err` to be defined');
+    }
+
+    expect(err.message).toEqual(
+      'The package `@vercel/does-not-exist` is not published on the npm registry'
+    );
+    expect((err as any).link).toEqual(
+      'https://vercel.link/builder-dependencies-install-failed'
+    );
+  });
+
   it('should import legacy `@now/build-utils` Builders', async () => {
     if (process.platform === 'win32') {
       // this test creates symlinks which require admin by default on Windows