Rework SQLMesh templater and add SM01-03 linting rules by barradasCouto · Pull Request #7722 · sqlfluff/sqlfluff

barradasCouto · 2026-04-08T11:51:44Z

Brief summary of the change made

Templater: Replaces _build_source_mapping, _find_model_block_end, and _coalesce_diff_opcodes with Context.render() + slice_file(). Sets templates_in_worker=False for deterministic context lifecycle. Adds proper teardown via _update_runtime_context() / _clear_cached_sqlmesh_context(). Lazy %s logging, narrowed exceptions, full type annotations.

Rules (new):

SM01 – Forbid 1=1 tautology in WHERE clauses
SM02 – Require explicit CAST for aliased SELECT expressions
SM03 – Forbid AD_HOC catalog references

Registered via get_rules() hookimpl in __init__.py.

Tests: Rewritten templater tests, full parametrized coverage for SM01–SM03, CV09 integration test, new python_model.py fixture.

Bumps plugin version 3.5.0 → 4.1.0.

Are there any other side effects of this change that we should be aware of?

None. All changes are scoped to the plugins/sqlfluff-templater-sqlmesh/ directory.

Pull Request checklist

Please confirm you have completed any of the necessary steps below.
Included test cases to demonstrate any code changes, which may be one or more of the following:
- .yml rule test cases in test/fixtures/rules/std_rule_cases.
- .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).
- Full autofix test cases in test/fixtures/linter/autofix.
- Other: plugin-scoped tests in plugins/sqlfluff-templater-sqlmesh/test/ (40 tests, all passing).
Added appropriate documentation for the change.

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Pull request overview

This PR updates the sqlfluff-templater-sqlmesh plugin to use SQLMesh’s Context.render() + SQLFluff slicing for templated/source mapping, and introduces three SQLMesh-specific linting rules (SM01–SM03) with accompanying fixtures and integration tests.

Changes:

Reworks the SQLMesh templater implementation and runtime context lifecycle (including deterministic templates_in_worker=False).
Adds new rules SM01 (1=1), SM02 (CAST required for aliased select expressions), SM03 (forbid AD_HOC catalog references) and registers them via plugin hooks.
Expands plugin-scoped test suite with integration tests and SQLMesh fixture projects/output.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
pyproject.toml	Adds `sqlmesh` keyword for package metadata discoverability.
plugins/sqlfluff-templater-sqlmesh/README.md	Adds plugin README entry.
plugins/sqlfluff-templater-sqlmesh/pyproject.toml	Bumps plugin version and declares `sqlmesh` dependency.
plugins/sqlfluff-templater-sqlmesh/sqlfluff_templater_sqlmesh/init.py	Registers templater + SM01–SM03 rules via plugin hooks.
plugins/sqlfluff-templater-sqlmesh/sqlfluff_templater_sqlmesh/templater.py	New templater implementation using `Context.render()` + `slice_file()` and cached context handling.
plugins/sqlfluff-templater-sqlmesh/sqlfluff_templater_sqlmesh/rules.py	Adds SM01–SM03 rule implementations.
plugins/sqlfluff-templater-sqlmesh/test/init.py	Adds test package marker.
plugins/sqlfluff-templater-sqlmesh/test/basic_test.py	Basic sanity tests for templater properties and version reporting.
plugins/sqlfluff-templater-sqlmesh/test/fixtures_test.py	Adds fixture-structure and (optional) SQLMesh render tests.
plugins/sqlfluff-templater-sqlmesh/test/integration_test.py	Adds integration tests for model name extraction, literal fallback, and context creation.
plugins/sqlfluff-templater-sqlmesh/test/rules_test.py	Adds unit tests for SM01–SM03 and rule execution with SQLMesh templating.
plugins/sqlfluff-templater-sqlmesh/test/templater_integration_test.py	Adds end-to-end linter/templater integration and slice integrity tests.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/.sqlfluff	Adds fixture-local SQLFluff config selecting `sqlmesh` templater.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/config.py	Adds SQLMesh project config fixture (python config).
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/macros/custom_macros.sql	Adds SQLMesh macro fixtures used by models.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/models/simple_model.sql	Adds SQLMesh model fixture.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/models/model_with_macros.sql	Adds SQLMesh model fixture exercising macros/variables.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/models/incremental_model.sql	Adds SQLMesh incremental model fixture.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/models/python_model.py	Adds SQLMesh Python model fixture.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/templated_output/simple_model.sql	Adds expected rendered SQL fixture output.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/templated_output/model_with_macros.sql	Adds expected rendered SQL fixture output.
plugins/sqlfluff-templater-sqlmesh/test/fixtures/sqlmesh/templated_output/incremental_model.sql	Adds expected rendered SQL fixture output.

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Copilot · 2026-04-11T05:27:55Z

+        except (SQLFluffSkipFile, SQLTemplaterError, ValueError) as err:
+            templater_logger.warning(
+                "Failed to create slice mapping for %s: %s. Using literal mapping.",
+                fname,
+                err,
+            )
+            return self._create_literal_templated_file(
+                fname,
+                rendered_sql,
+                source_content=in_str,
+                was_rendered=False,
+            )


When slice_file() fails after successful SQLMesh rendering, the fallback calls _create_literal_templated_file(..., templated_content=rendered_sql, source_content=in_str, was_rendered=False). Because source and templated content differ, treating this as a literal slice risks incorrect source↔templated position mapping and potentially unsafe/misapplied fixes. Consider marking this fallback as rendered/templated so SQLFluff won’t treat the whole file as safely literal-mappable.

@copilot apply changes based on this feedback

Copilot · 2026-04-11T05:27:56Z

+    crawl_behaviour = SegmentSeekerCrawler({"comparison_operator"})
+    is_fix_compatible = False
+
+    def _eval(self, context: RuleContext) -> Optional[LintResult]:
+        """Flag constant true ``1 = 1`` comparisons."""
+        if context.segment.raw != "=":
+            return None
+
+        expression = next(
+            (
+                segment
+                for segment in reversed(context.parent_stack)
+                if segment.is_type("expression")
+            ),
+            None,
+        )
+        if expression is None:
+            return None


PR description says SM01 forbids the 1=1 tautology specifically in WHERE clauses, but the implementation crawls all comparison_operator segments and will flag 1 = 1 anywhere in an expression (e.g., JOIN conditions, CASE expressions). Either update the rule to confirm the comparison is within a where_clause (or similar) in parent_stack, or adjust the rule description/docs/tests to match the broader scope.

Copilot · 2026-04-11T05:27:56Z

+        if segment.get_child("wildcard_expression") is not None:
+            return None
+
+        if any(segment.recursive_crawl("cast_expression")):
+            return None
+
+        if self._has_cast_like_function(segment):
+            return None
+


SM02 currently treats an aliased select element as compliant if it contains any cast_expression anywhere within the element. This will allow cases where only a sub-expression is cast (e.g., casting an argument inside a function) rather than explicitly casting the final projected expression. If the intent is to require the outermost expression to be cast, tighten the check to validate the top-level expression before the alias is a cast (or a cast-like function wrapping the expression).

@copilot apply changes based on this feedback

Copilot · 2026-04-11T05:27:57Z

+def execute(
+    context: ExecutionContext,
+    start: t.Optional[str] = None,
+    end: t.Optional[str] = None,
+    **kwargs: t.Any,
+) -> t.Dict[str, t.Any]:
+    """Execute the Python model."""
+    # Fetch data from upstream model
+    df = context.fetchdf("SELECT * FROM source_table")
+
+    # Add computed column
+    df["computed_value"] = df["id"] * 2.5
+
+    return df


The execute() function return type annotation doesn’t match what the function returns: it is annotated as Dict[str, Any] but returns df (a DataFrame from context.fetchdf()). Update the annotation (and/or the return value) so the fixture is internally consistent and matches SQLMesh’s expected Python model contract.

@copilot apply changes based on this feedback

@barradasCouto I believe you need individual Copilot subscription or repo maintaner role for this

github-actions · 2026-04-11T05:45:00Z

Coverage Results ✅

Name    Stmts   Miss  Cover   Missing
-------------------------------------
TOTAL   21600      0   100%

263 files skipped due to complete coverage.

peterbud · 2026-04-18T09:30:49Z

Hi @barradasCouto - thanks for opening this PR and welcome.
Are you planning to address the feedback from Copilot?

lovely copilot adding things no one asked for

greptile-apps Bot reviewed Apr 8, 2026

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barradasCouto mentioned this pull request Apr 8, 2026

Basic SQLMesh templater plugin with tests and docs #7719

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peterbud requested a review from Copilot April 11, 2026 05:22

Copilot started reviewing on behalf of peterbud April 11, 2026 05:23 View session

Copilot AI reviewed Apr 11, 2026

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WittierDinosaur and others added 5 commits April 27, 2026 00:23

Implement SQLMesh Templater

7978c27

Update templater

7954497

Rework SQLMesh templater and add SM01-03 linting rules

bbe9f6d

Delete plugins/sqlfluff-templater-sqlmesh/LICENSE.md

c09c6f0

lovely copilot adding things no one asked for

Address SQLMesh templater review feedback

9ea3864

barradasCouto force-pushed the sqlmesh-linter branch from e83d31b to 9ea3864 Compare April 27, 2026 00:52

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barradasCouto commented Apr 8, 2026

Brief summary of the change made

Are there any other side effects of this change that we should be aware of?

Pull Request checklist

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