Introduce randomized testing for queries, fix the revealed bugs #1496
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Randomized testing is already used in Tree-sitter's test suite for verify that incremental parsing behaves correctly. But previously, Tree-sitter's query engine was only tested via hand-written examples. This PR adds some limited randomized testing of the query engine.
Strategy
The new tests use the following procedure:
Findings
This test found a number of patterns which gave false "impossible pattern" errors when constructing queries, due to bugs in the query analysis. They also surfaced a number of places where we were unnecessarily splitting match states, which ultimately resulted in incorrectly-ordered results.
Limitations
The test that's checked-in has some restrictions:
Next Steps
After this, it'll be easy to gradually enhance the randomized tests to exercise more languages, more example files, and more of the query syntax. We should also test iterating through captures, not just matches.