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• [fix] Support boolean values for client.showErrorLinks config option #13806 👈 (View in Graphite)
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Summary

This PR fixes the client.showErrorLinks config option to accept boolean values (True/False) in addition to string values ("auto", "true", "false"). Previously, setting the config option with a boolean like client.showErrorLinks = false in config.toml would fail because the code only checked for string values. This is a valid bug because TOML distinguishes between false (boolean) and "false" (string).

Files changed:

• lib/streamlit/runtime/app_session.py - Added boolean handling in _get_show_error_links()
• lib/tests/streamlit/runtime/app_session_test.py - Added unit tests for boolean values

Code Quality

The implementation is clean and follows existing patterns in the codebase:

1. Correct use of identity comparison: Using is True and is False (rather than truthiness checks) is the correct approach here because:

   • It explicitly matches only Python boolean values
   • It avoids accidentally matching other truthy/falsy values like strings
   • This pattern is used elsewhere in the codebase (e.g., line 1041 for client.showSidebarNavigation)

2. Clear code organization: The boolean checks are placed before the string checks with a helpful comment explaining the two sources of config values (programmatic vs. config.toml/CLI).

3. No unnecessary changes: The PR is focused and makes only the minimum required changes.

Test Coverage

The test coverage is adequate:

• test_bool_true: Verifies boolean True returns SHOW_ERROR_LINKS_TRUE
• test_bool_false: Verifies boolean False returns SHOW_ERROR_LINKS_FALSE

The tests follow the existing pattern in the GetShowErrorLinksTest class and include appropriate docstrings. The existing tests already cover:

• String values: "auto", "true", "false"
• Invalid string values raise ValueError

Note on anti-regression assertions: The Python test guidelines recommend including negative assertions when practical. While the new tests don't include explicit assertions that other enum values are NOT returned, this is consistent with the existing tests in the same class. The assertion equality check implicitly validates this.

Backwards Compatibility

Fully backwards compatible. This change only adds new functionality without modifying existing behavior:

• String values ("auto", "true", "false") continue to work exactly as before
• Invalid values still raise ValueError with the same error message
• The default value "auto" is unaffected

The boolean handling is checked first, so it takes priority, but since booleans and strings are distinct types in Python, this cannot interfere with existing string-based configurations.

Security & Risk

Low risk. This is a straightforward bug fix with:

• No security implications (config option affects only UI error display)
• No external dependencies affected
• Clear scope limited to one config option
• Well-tested behavior

Edge cases handled correctly:

• None would pass through to string validation and raise ValueError (correct)
• Integers 0/1 would similarly raise ValueError (correct, since 0 is False returns False in Python)

Recommendations

No required changes. The PR is ready for merge.

Optional improvements (not blocking):

1. Consider updating the config option docstring in lib/streamlit/config.py (line 622-625) to explicitly mention that boolean values are also accepted, though the current description is technically correct since TOML treats unquoted true/false as booleans.

2. For completeness, you could add a test for None to verify it raises ValueError, but this is an edge case that's already covered by the invalid value test logic.

Verdict

APPROVED: Clean, well-tested bug fix that correctly handles boolean config values from TOML files while maintaining full backwards compatibility with existing string-based configurations.

This is an automated AI review using opus-4.5-thinking. Please verify the feedback and use your judgment.

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