Moving an apply-time SQL error to a plan-time validation error, in a two-year-old issue.
Resposta curta
The materialize_source_kafka resource let you set format together with key_format, which Materialize does not accept, so terraform apply failed with a SQL syntax error. The fix adds ConflictsWith and RequiredWith rules to the schema, so Terraform rejects invalid combinations during plan. It was merged as PR #947 and closed issue #654, which had been open since September 2024.
The problem
Issue #654 showed a Kafka source with both format { json = true } and key_format { json = true }. Applying it failed with:
Error: ERROR: Expected end of statement, found KEY (SQLSTATE 42601)The issue already proposed the fix: add a ConflictsWith so format can't be combined with key_format and value_format.
The fix
"format": func() *schema.Schema {
...
s.ConflictsWith = []string{"key_format", "value_format"}
return s
}(),
"key_format": func() *schema.Schema {
...
s.ConflictsWith = []string{"format"}
s.RequiredWith = []string{"value_format"}
return s
}(),
"value_format": func() *schema.Schema {
...
s.ConflictsWith = []string{"format"}
s.RequiredWith = []string{"key_format"}
return s
}(),According to the PR description, these constraints match the ones already used by materialize_source_table_kafka. The attribute descriptions and generated docs now spell the rules out.
By the numbers
- Repository: MaterializeInc/terraform-provider-materialize, 14 stars (Nov 3, 2026), Go, MPL-2.0
- Files changed: 4
- Lines: +70 / -6
- Commits: 2 (1 from the PR author, 1 from a maintainer)
- Opened: Oct 6, 2026. Merged: Oct 10, 2026. Time to merge: 3 days, 20 hours
- Review: approved and merged by a maintainer
How the review went
The maintainer who filed the original issue approved the PR and added a commit of their own: "Test the Kafka source format rules through validation, regenerate docs, and add a changelog entry." That commit replaced the PR's original 14-line test with a table-driven test that runs the resource's Validate and checks for errors on each combination. The changelog entry reads, in part, "these failed at apply with a syntax error; they are now rejected at plan time."
Perguntas frequentes
Is this resource still recommended?
These format attributes are marked deprecated in the provider, which points users to materialize_source_table_kafka. The fix makes the deprecated path fail early and clearly.
Where can I read more?
See the pull request and the original issue.
O objetivo
Infrastructure tools should fail at plan, not halfway through apply. Here the schema fix was small, and the maintainer reshaped the test to match how the project tests validation.
