use .env.local for tests (#19542)

[zimirza]

What does this PR do?

This pull request fixes an issue that when running bun test, .env.local was not read for the environment variables. This pull request closes #19542.

How did you verify your code works?

• I checked the lifetime of memory allocated to verify it's (1) freed and (2) only freed when it should be
• I included a test for the new code, or an existing test covers it
• JSValue used outside of the stack is either wrapped in a JSC.Strong or is JSValueProtect'ed
• I updated TypeScript/JavaScript tests and they pass locally (test/cli/run/env.test.ts)

[zimirza]

I am not sure if this is the correct approach, that .env.local is read last of the local environment variables files.

[jakswa]

I think i just ran into this too -- confusing env var loading in my tests. You go to make sure you understand the basic precedence outlined in the bun docs and you get confusing behavior right now.

[zimirza]

I have updated such that .env.local is read last for tests. However, one test does not really work:

  test(".env.local overrides .env.{NODE_ENV}", () => {
    const dir = tempDirWithFiles("dotenv", {
      ".env": "FOO=.env\n",
      ".env.development": "FOO=.env.development\n",
      ".env.production": "FOO=.env.production\n",
      ".env.test": "FOO=.env.test\n",
      ".env.local": "FOO=.env.local\n",
      "index.ts": "console.log(process.env.FOO);",
      "index.test.ts": "console.log(process.env.FOO);",
    });
    const { stdout: stdout_dev } = bunRun(`${dir}/index.ts`, { NODE_ENV: "development" });
    expect(stdout_dev).toBe(".env.local");
    const { stdout: stdout_prod } = bunRun(`${dir}/index.ts`, { NODE_ENV: "production" });
    expect(stdout_prod).toBe(".env.local");
    const { stdout: stdout_test } = bunTest(`${dir}/index.test.ts`, {});
    expect(stdout_test).toBe(`bun test ${Bun.version_with_sha}\n` + ".env.local");
  });

The last test should be .env.local, and returns with .env.test.

[zimirza]

I think i fixed it for tests to use .env.local. Tests are working now.