<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/106459>106459</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [mlir][polly][llvm-lit] External shell unable to be turned on for lit tests
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            mlir
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          connieyzhu
      </td>
    </tr>
</table>

<pre>
    In both mlir and polly, tests are run with lit's internal shell by default. In order to use the external shell instead, the `LIT_USE_INTERNAL_SHELL` environment variable should be set to 0. The logic in the lit configs of these test suites prevents the external shell from being turned on.

Code:
```
use_lit_shell = True
lit_shell_env = os.environ.get("LIT_USE_INTERNAL_SHELL")
if lit_shell_env:
        use_lit_shell = not lit.util.pythonize_bool(lit_shell_env)

config.test_format = lit.formats.ShTest(execute_external=not use_lit_shell)
```

The problem lies in the body of the if statement, with the use of `not`.
</pre>
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