chore: remove proxyquire-bun-shim.cjs and runner flags (#9646)

## Description

Removes bin/proxyquire-bun-shim.cjs and all remaining Mocha and runner
shim configuration.

## Impact

Eliminates the global Bun proxyquire preload shim from the test runner.

## Changes

- **Part 5 of 5 in stacked PR series**: #9642 -> #9643 -> #9644 -> #9645
-> **#9646** (b/570680750).
- Stacked on #9645.
- Delete `bin/proxyquire-bun-shim.cjs`.
- Remove `--proxyquire-shim`, `BUN_ENABLE_PROXYQUIRE_SHIM`, and
`proxyquire-bun-shim.cjs` preloading from `bin/run-test.cjs`.
- Remove `proxyquire-bun-shim.cjs` from `.mocharc.cjs` and all 11
`core/packages/*/.mocharc.js` configuration files.

## Testing

- Verified unit tests across all migrated packages pass under both
Node.js and Bun (`JS_RUNTIME=bun`) without
`bin/proxyquire-bun-shim.cjs`.
- Verified strict lint and type checks pass via `bin/linter.mjs
--strict`.

## Alternatives

- Not merging this pull request was considered, which would leave dead
shim code and unused `--proxyquire-shim` runner flags in the repository.

Author: danieljbruce

.mocharc.cjs

@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-const path = require('path');
-
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -28,7 +26,6 @@ if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
 if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, 'bin/proxyquire-bun-shim.cjs')];
   config.exit = true;
 }
 if (process.env.MOCHA_REPORTER) {

bin/proxyquire-bun-shim.cjs

@@ -20,10 +20,9 @@
 //   coverage and Mocha worker-thread parallelism (`parallel: true`).
 // - Under Bun (`typeof Bun !== 'undefined'` or `JS_RUNTIME === 'bun'`):
 //   Skips `c8` (which relies on Node's `NODE_V8_COVERAGE`), disables Mocha
-//   worker-thread parallelism (`--no-parallel`), preloads the Bun `proxyquire`
-//   shim (`bin/proxyquire-bun-shim.cjs`) when `--proxyquire-shim` is passed,
-//   and loads `mocha/bin/mocha.js` directly in-process so `#!/usr/bin/env node`
-//   shebangs never switch back to Node.js.
+//   worker-thread parallelism (`--no-parallel`), and loads `mocha/bin/mocha.js`
+//   directly in-process so `#!/usr/bin/env node` shebangs never switch back to
+//   Node.js.
 'use strict';
 
 const {spawnSync} = require('child_process');
@@ -32,26 +31,7 @@ const fs = require('fs');
 
 const rawArgs = process.argv.slice(2);
 const noC8 = rawArgs.includes('--no-c8');
-
-const SHIM_FLAGS = [
-  {
-    flag: '--proxyquire-shim',
-    envIn: 'BUN_PROXYQUIRE_SHIM',
-    envOut: 'BUN_ENABLE_PROXYQUIRE_SHIM',
-  },
-];
-
-const shimFlagSet = new Set(SHIM_FLAGS.map(s => s.flag));
-const shimEnvVars = {};
-for (const {flag, envIn, envOut} of SHIM_FLAGS) {
-  const enabled =
-    rawArgs.includes(flag) ||
-    process.env[envIn] === 'true' ||
-    process.env[envOut] === 'true';
-  shimEnvVars[envOut] = enabled ? 'true' : 'false';
-}
-
-const args = rawArgs.filter(a => a !== '--no-c8' && !shimFlagSet.has(a));
+const args = rawArgs.filter(a => a !== '--no-c8');
 
 const isBunRuntime = typeof Bun !== 'undefined';
 const isBunUserAgent = /^bun\//i.test(process.env.npm_config_user_agent || '');
@@ -650,7 +630,6 @@ if (require.main === module) {
 
   if (wantsBunRuntime) {
     process.env.MOCHA_PARALLEL = 'false';
-    Object.assign(process.env, shimEnvVars);
 
     // If Bun was requested (via JS_RUNTIME=bun or `bun run test`) but this
     // script was launched via Node.js, re-exec under the `bun` binary.
@@ -660,7 +639,6 @@ if (require.main === module) {
         env: {
           ...process.env,
           MOCHA_PARALLEL: 'false',
-          ...shimEnvVars,
         },
       });
       if (res.error) {
@@ -678,15 +656,6 @@ if (require.main === module) {
       mochaArgs.unshift('--no-parallel');
     }
 
-    // Only preload the proxyquire shim when `--proxyquire-shim` is requested.
-    if (shimEnvVars.BUN_ENABLE_PROXYQUIRE_SHIM === 'true') {
-      const shimPath = path.resolve(__dirname, 'proxyquire-bun-shim.cjs');
-      require(shimPath);
-      if (!mochaArgs.includes(shimPath)) {
-        mochaArgs.unshift('--require', shimPath);
-      }
-    }
-
     if (!mochaArgs.includes('--exit')) {
       mochaArgs.unshift('--exit');
     }

bin/run-test.cjs

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,9 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }

core/packages/gapic-node-processing/.mocharc.js

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,10 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  // Preload Bun compatibility shim for proxyquire and nock when running under Bun
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }

core/packages/gax/.mocharc.js

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,9 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }

core/packages/gaxios/.mocharc.js

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,9 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }

core/packages/gcp-metadata/.mocharc.js

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,9 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }

core/packages/google-auth-library-nodejs/.mocharc.js

@@ -11,7 +11,6 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-const path = require('path');
 const config = {
   "enable-source-maps": true,
   "throw-deprecation": true,
@@ -24,9 +23,6 @@ if (process.env.MOCHA_THROW_DEPRECATION === 'false') {
 if (process.env.MOCHA_PARALLEL === 'false' || typeof Bun !== 'undefined') {
   config.parallel = false;
 }
-if (typeof Bun !== 'undefined') {
-  config.require = [path.resolve(__dirname, '../../../bin/proxyquire-bun-shim.cjs')];
-}
 if (process.env.MOCHA_REPORTER) {
   config.reporter = process.env.MOCHA_REPORTER;
 }