Conformance

Upstream Tree-sitter (C) is a behavioral reference, not a dependency: no C compiles into the package and no symbols are linked. Conformance is enforced by a differential corpus harness, not just hand-written tests.

The corpus

Cases live in src/debug/corpus/*.txt. Parse cases declare a grammar, a source, and the expected S-expression:

# grammar: expression
# name: precedence
---source---
1 + 2 * 3
---sexp---
(program (expression (expression (term (factor (number "1")))) "+" ...))

Incremental cases declare an edit triple plus the new source, and require the incremental reparse to be byte-identical to a fresh parse:

# grammar: expression
# name: trailing growth
---source---
1 + 2
---edit---
5 5 6
---source---
1 + 22

Running it

zig build conformance   # human-readable PASS/FAIL report (exit 1 on failure)
zig build test          # the same cases run as the "conformance: corpus cases pass" test

The case list is embedded once (conformance.corpus_files), so the report and the test suite cannot drift apart. This harness caught a real reuse-cloning bug during development (bushy subtree clones corrupted incremental trees while weak count assertions passed) — see Incremental Runtime.

Adding a case

Add a *.txt file in src/debug/corpus/, list it in corpus_files, and run both commands. Verify the expected S-expression against the grammar tables by hand before locking it in — the corpus is a reference, not an oracle.

Related: Upstream Conformance, Testing, S-expressions.