use tmp dir for external queries test

src/external-queries.test.ts

@@ -3,15 +3,19 @@ import * as path from "path";
 
 import * as configUtils from "./config-utils";
 import * as externalQueries from "./external-queries";
+import * as util from "./util";
 
 test("checkoutExternalQueries", async () => {
     let config = new configUtils.Config();
     config.externalQueries = [
         new configUtils.ExternalQuery("github/codeql-go", "df4c6869212341b601005567381944ed90906b6b"),
     ];
-    await externalQueries.checkoutExternalQueries(config);
 
-    let destination = process.env["RUNNER_WORKSPACE"] || "/tmp/codeql-action/";
-    // COPYRIGHT file existed in df4c6869212341b601005567381944ed90906b6b but not in master
-    expect(fs.existsSync(path.join(destination, "github", "codeql-go", "COPYRIGHT"))).toBeTruthy();
+    await util.withTmpDir(async tmpDir => {
+        process.env["RUNNER_WORKSPACE"] = tmpDir;
+        await externalQueries.checkoutExternalQueries(config);
+
+        // COPYRIGHT file existed in df4c6869212341b601005567381944ed90906b6b but not in master
+        expect(fs.existsSync(path.join(tmpDir, "github", "codeql-go", "COPYRIGHT"))).toBeTruthy();
+    });
 });

src/external-queries.ts

@@ -4,9 +4,10 @@ import * as fs from 'fs';
 import * as path from 'path';
 
 import * as configUtils from './config-utils';
+import * as util from './util';
 
 export async function checkoutExternalQueries(config: configUtils.Config) {
-  const folder = process.env['RUNNER_WORKSPACE'] || '/tmp/codeql-action';
+  const folder = util.getRequiredEnvParam('RUNNER_WORKSPACE');
 
   for (const externalQuery of config.externalQueries) {
     core.info('Checking out ' + externalQuery.repository);

src/util.ts

@@ -3,6 +3,8 @@ import * as http from '@actions/http-client';
 import * as auth from '@actions/http-client/auth';
 import * as octokit from '@octokit/rest';
 import consoleLogLevel from 'console-log-level';
+import * as fs from "fs";
+import * as os from 'os';
 import * as path from 'path';
 
 import * as sharedEnv from './shared-environment';
@@ -313,3 +315,11 @@ export function getToolNames(sarifContents: string): string[] {
 
     return Object.keys(toolNames);
 }
+
+// Creates a random temporary directory, runs the given body, and then deletes the directory.
+// Mostly intended for use within tests.
+export async function withTmpDir(body: (tmpDir: string) => Promise<void>) {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'codeql-action-'));
+    await body(tmpDir);
+    fs.rmdirSync(tmpDir, { recursive: true });
+}