fix(citations): honor the errs tolerance cap in CitationMixin fuzzy span matching

instructor/v2/dsl/citation.py

@@ -85,7 +85,7 @@ def _get_span(
 
         errs_ = 0
         s = regex.search(f"({minor}){{e<={errs_}}}", major)
-        while s is None and errs_ <= errs:
+        while s is None and errs_ < errs:
             errs_ += 1
             s = regex.search(f"({minor}){{e<={errs_}}}", major)
 

tests/dsl/test_citation.py

@@ -0,0 +1,26 @@
+"""Tests for CitationMixin fuzzy span matching tolerance."""
+
+from instructor.v2.dsl.citation import CitationMixin
+
+
+class _Answer(CitationMixin):
+    pass
+
+
+def test_quote_within_error_tolerance_matches():
+    # 3 substitutions from the 10-char source (<= errs default of 5): should match.
+    context = "0123456789"
+    result = _Answer.model_validate(
+        {"substring_quotes": ["0123456ZZZ"]}, context={"context": context}
+    )
+    assert result.substring_quotes == ["0123456789"]
+
+
+def test_quote_beyond_error_tolerance_is_dropped():
+    # 6 substitutions from the 10-char source (> errs default of 5): should be
+    # dropped as "not found", not accepted and rewritten to an unrelated span.
+    context = "0123456789"
+    result = _Answer.model_validate(
+        {"substring_quotes": ["0123ZZZZZZ"]}, context={"context": context}
+    )
+    assert result.substring_quotes == []