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feat: Add example rows to ValidationError for all rule failures #286

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Initial plan
Copilot Feb 28, 2026
f26224a
feat: enhance primary_key ValidationError with distinct combinations …
Copilot Feb 28, 2026
462f8ce
feat: extend examples to all rules in both eager and lazy validation …
Copilot Feb 28, 2026
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19 changes: 16 additions & 3 deletions dataframely/schema.py
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Original file line number Diff line number Diff line change
Expand Up @@ -572,9 +572,22 @@ def validate(
if eager:
out, failure = cls.filter(df, cast=cast, eager=True)
if len(failure) > 0:
raise ValidationError(
format_rule_failures(list(failure.counts().items()))
)
counts = failure.counts()
msg = format_rule_failures(list(counts.items()))
if "primary_key" in counts:
pk_cols = cls.primary_key()
distinct_duplicate_keys = (
failure._df.filter(pl.col("primary_key").not_())
.select(pk_cols)
.unique()
)
n_distinct = len(distinct_duplicate_keys)
examples = distinct_duplicate_keys.head(5).to_dicts()
suffix = "combination" if n_distinct == 1 else "combinations"
old = f"'primary_key' failed for {counts['primary_key']:,} rows"
new = old + f" with {n_distinct} distinct {suffix}, examples: {examples}"
msg = msg.replace(old, new)
raise ValidationError(msg)
return out
else:
lf = df.lazy().pipe(
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4 changes: 3 additions & 1 deletion tests/schema/test_validate.py
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Original file line number Diff line number Diff line change
Expand Up @@ -130,8 +130,10 @@ def test_invalid_primary_key(
with pytest.raises(
ValidationError if eager else plexc.ComputeError,
match=r"1 rules failed validation",
):
) as exc_info:
_validate_and_collect(MySchema, df, eager=eager)
if eager:
exc_info.match(r"with 1 distinct combination, examples: \[")
assert not MySchema.is_valid(df)


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