Fix unclear error when missing dependencies

RELEASE.md

@@ -0,0 +1,6 @@
+Release type: minor
+
+When calling the CLI without all the necessary dependencies installed,
+a `MissingOptionalDependenciesError` will be raised instead of a
+`ModuleNotFoundError`. This new exception will provide a more helpful
+hint regarding how to fix the problem.

strawberry/cli/__init__.py

@@ -1,11 +1,15 @@
-from .commands.codegen import codegen as codegen  # noqa
-from .commands.export_schema import export_schema as export_schema  # noqa
-from .commands.server import server as server  # noqa
-from .commands.upgrade import upgrade as upgrade  # noqa
-from .commands.schema_codegen import schema_codegen as schema_codegen  # noqa
+try:
+    from .app import app
+    from .commands.codegen import codegen as codegen  # noqa
+    from .commands.export_schema import export_schema as export_schema  # noqa
+    from .commands.schema_codegen import schema_codegen as schema_codegen  # noqa
+    from .commands.server import server as server  # noqa
+    from .commands.upgrade import upgrade as upgrade  # noqa
 
-from .app import app
+    def run() -> None:
+        app()
 
+except ModuleNotFoundError as exc:
+    from strawberry.exceptions import MissingOptionalDependenciesError
 
-def run() -> None:
-    app()
+    raise MissingOptionalDependenciesError(extras=["cli"]) from exc

strawberry/exceptions/__init__.py

@@ -12,6 +12,7 @@
 from .invalid_argument_type import InvalidArgumentTypeError
 from .invalid_union_type import InvalidTypeForUnionMergeError, InvalidUnionTypeError
 from .missing_arguments_annotations import MissingArgumentsAnnotationsError
+from .missing_dependencies import MissingOptionalDependenciesError
 from .missing_field_annotation import MissingFieldAnnotationError
 from .missing_return_annotation import MissingReturnAnnotationError
 from .not_a_strawberry_enum import NotAStrawberryEnumError
@@ -186,4 +187,5 @@ class StrawberryGraphQLError(GraphQLError):
     "MissingFieldAnnotationError",
     "DuplicatedTypeName",
     "StrawberryGraphQLError",
+    "MissingOptionalDependenciesError",
 ]

strawberry/exceptions/missing_dependencies.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from typing import Optional
+
+
+class MissingOptionalDependenciesError(Exception):
+    """Some optional dependencies that are required for a particular
+    task are missing."""
+
+    def __init__(
+        self,
+        *,
+        packages: Optional[list[str]] = None,
+        extras: Optional[list[str]] = None,
+    ) -> None:
+        packages = packages or []
+        if extras:
+            packages.append(f"'strawberry-graphql[{','.join(extras)}]'")
+        hint = f" (hint: pip install {' '.join(packages)})" if packages else ""
+        self.message = f"Some optional dependencies are missing{hint}"

tests/exceptions/classes/test_exception_class_missing_optional_dependencies_error.py

@@ -0,0 +1,57 @@
+import pytest
+
+from strawberry.exceptions import MissingOptionalDependenciesError
+
+
+def test_missing_optional_dependencies_error():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError()
+
+    assert exc_info.value.message == "Some optional dependencies are missing"
+
+
+def test_missing_optional_dependencies_error_packages():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError(packages=["a", "b"])
+
+    assert (
+        exc_info.value.message
+        == "Some optional dependencies are missing (hint: pip install a b)"
+    )
+
+
+def test_missing_optional_dependencies_error_empty_packages():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError(packages=[])
+
+    assert exc_info.value.message == "Some optional dependencies are missing"
+
+
+def test_missing_optional_dependencies_error_extras():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError(extras=["dev", "test"])
+
+    assert (
+        exc_info.value.message
+        == "Some optional dependencies are missing (hint: pip install 'strawberry-graphql[dev,test]')"
+    )
+
+
+def test_missing_optional_dependencies_error_empty_extras():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError(extras=[])
+
+    assert exc_info.value.message == "Some optional dependencies are missing"
+
+
+def test_missing_optional_dependencies_error_packages_and_extras():
+    with pytest.raises(MissingOptionalDependenciesError) as exc_info:
+        raise MissingOptionalDependenciesError(
+            packages=["a", "b"],
+            extras=["dev", "test"],
+        )
+
+    assert (
+        exc_info.value.message
+        == "Some optional dependencies are missing (hint: pip install a b 'strawberry-graphql[dev,test]')"
+    )