Add crossplane-namespace tag to managed resources

[Scrumplex]

Description of your changes

Since Crossplane v2 supports namespaced resources, it is quite fitting to also
mention the namespace of a resource in its tags.

I have:

• Read and followed Crossplane's contribution process.
• Run earthly +reviewable to ensure this PR is ready for review.
• Added or updated unit tests.
• Linked a PR or a docs tracking issue to document this change.
• Added backport release-x.y labels to auto-backport this PR.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a new exported tag key for namespace and updates GetExternalTags to include the object’s namespace when present. Introduces a corresponding test case verifying the namespace tag is populated for namespaced objects.

Changes

Cohort / File(s)	Summary
Tagging logic pkg/resource/resource.go	Adds ExternalResourceTagKeyNamespace constant and updates GetExternalTags to set the namespace tag when mg.GetNamespace() is non-empty.
Unit tests pkg/resource/resource_test.go	Adds "SuccessfulWithNamespacedObject" test case to assert inclusion of the namespace tag in external tags for namespaced objects.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Thanks for the update. One quick clarification: should cluster-scoped objects explicitly omit the namespace tag, or include it with an empty value for consistency?

Pre-merge checks

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title accurately reflects the main change by specifying that a crossplane-namespace tag is being added to managed resources and meets the under-72-character requirement.
Description Check	✅ Passed	The description clearly outlines the rationale for adding a namespace tag to managed resources, mentions the updated tests, and directly relates to the code changes.
Breaking Changes	✅ Passed	Thanks for adding the namespace tagging—it helps explain the motivation nicely. I reviewed the public API surface and the only change is the introduction of the new exported constant ExternalResourceTagKeyNamespace, while existing exported functions, types, methods, and fields retain their names, signatures, and behavior. Since no public elements were removed or altered incompatibly, the Breaking Changes check passes without needing the label.

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📜 Recent review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3f03019 and 89bbbbb.

📒 Files selected for processing (2)

• pkg/resource/resource.go (2 hunks)
• pkg/resource/resource_test.go (1 hunks)

🧰 Additional context used

📓 Path-based instructions (2)

**/*.go

⚙️ CodeRabbit configuration file

**/*.go: Enforce Crossplane-specific patterns: Use crossplane-runtime/pkg/errors
for wrapping. Check variable naming (short for local scope, descriptive
for wider scope). Ensure 'return early' pattern. Verify error scoping
(declare in conditionals when possible). For nolint directives, require
specific linter names and explanations. CRITICAL: Ensure all error
messages are meaningful to end users, not just developers - avoid
technical jargon, include context about what the user was trying to do,
and suggest next steps when possible.

Files:

• pkg/resource/resource.go
• pkg/resource/resource_test.go

**/*_test.go

⚙️ CodeRabbit configuration file

**/*_test.go: Enforce table-driven test structure: PascalCase test names (no
underscores), args/want pattern, use cmp.Diff with
cmpopts.EquateErrors() for error testing. Check for proper test case
naming and reason fields. Ensure no third-party test frameworks (no
Ginkgo, Gomega, Testify).

Files:

• pkg/resource/resource_test.go

🧬 Code graph analysis (1)

pkg/resource/resource_test.go (3)

pkg/resource/interfaces.go (3)

• ModernManaged (209-213)
• TypedProviderConfigReferencer (84-87)
• Managed (200-204)

pkg/resource/fake/mocks.go (3)

• ModernManaged (370-376)
• TypedProviderConfigReferencer (71-71)
• Managed (344-348)

pkg/resource/resource.go (5)

• ExternalResourceTagKeyKind (50-50)
• ExternalResourceTagKeyName (51-51)
• ExternalResourceTagKeyNamespace (52-52)
• ExternalResourceTagKeyProvider (53-53)
• ExternalResourceTagKeyProviderConfigKind (54-54)

🔇 Additional comments (3)

pkg/resource/resource.go (2)

52-52: LGTM! Constant naming is consistent.

The new constant follows the established naming pattern for external resource tag keys.

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418-420: Nice implementation using the declare-in-conditional pattern.

The code correctly:

• Declares the namespace variable in the conditional scope (as per coding guidelines)
• Only adds the tag when namespace is non-empty
• Maintains backward compatibility for cluster-scoped resources

This aligns well with Crossplane v2's support for namespaced resources.

pkg/resource/resource_test.go (1)

639-656: Excellent test coverage for the namespace functionality.

The test case properly verifies that:

• The namespace tag is included when the managed resource has a namespace
• All other tags are still populated correctly
• Follows the established table-driven test pattern with PascalCase naming

The existing test cases (like "SuccessfulWithTypedProviderConfig") already cover the scenario where namespace is empty, ensuring backward compatibility.

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[negz]

Makes sense to me!