feat: Add --replace flag to crossplane xrd generate

[BigGold1310]

Description of your changes

Adding a --replace flag to crossplane xrd generate command instructing it to create or if exists replace the definition.yaml file.

Fixes #216

I have:

• Read and followed Crossplane's contribution process.
• Run ./nix.sh flake check 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

The XRD generate command adds an optional --replace flag. Existing output files remain protected by default and are overwritten when replacement is enabled. Integration tests cover both behaviors and validate generated YAML.

Changes

XRD generation replacement

Layer / File(s)	Summary
Replacement option and file handling cmd/crossplane/xrd/generate.go	The command adds Replace. Existing files are replaced only when enabled; otherwise, the error references --path or --replace.
Command integration coverage cmd/crossplane/xrd/generate_test.go	Tests cover new-file generation, overwrite refusal, replacement, YAML parsing, resource naming, and isolated in-memory filesystems.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: haarchri

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes implement issue #216 by allowing crossplane xrd generate to replace an existing definition.yaml file.
Out of Scope Changes check	✅ Passed	The changes are limited to the --replace flag implementation and its unit tests.
Breaking Changes	✅ Passed	The diff changes only cmd/crossplane/xrd and adds an optional --replace flag; existing generation and no-overwrite behavior remain unchanged when the flag is absent.
Feature Gate Requirement	✅ Passed	The overwrite behavior is explicitly gated by generateCmd.Replace (--replace); without it existing files still error, so the behavior change has a feature flag.
Title check	✅ Passed	The title is 51 characters, stays under 72 characters, and clearly describes adding the --replace flag.
Description check	✅ Passed	The description clearly explains the --replace flag, its overwrite behavior, and the related unit tests.

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

cmd/crossplane/xrd/generate.go (1)

131-132: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Expose a stable existing-file error cause. The formatted-only error at cmd/crossplane/xrd/generate.go lines 131-132 forces text-based assertions in cmd/crossplane/xrd/generate_test.go.

• cmd/crossplane/xrd/generate.go#L131-L132: return or wrap a stable sentinel or typed existing-file error while preserving the actionable path and --replace context.
• cmd/crossplane/xrd/generate_test.go#L773-L827: add want.err and reason, then compare the stable error with cmp.Diff and cmpopts.EquateErrors().

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@cmd/crossplane/xrd/generate.go` around lines 131 - 132, Expose a stable
sentinel or typed existing-file error from the Replace check in
cmd/crossplane/xrd/generate.go lines 131-132, wrapping it while retaining the
file path and --replace guidance; update cmd/crossplane/xrd/generate_test.go
lines 773-827 to add want.err and reason fields and compare errors with cmp.Diff
and cmpopts.EquateErrors().

Source: Path instructions

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cmd/crossplane/xrd/generate_test.go`:
- Around line 800-810: Extend the tests around generateCmd.Run to invoke the
command through Kong parsing with the --replace flag instead of assigning
Replace directly, then assert the parsed command has replacement enabled and
preserves the existing replacement behavior. Use the generate command’s Kong
struct definition and normal xrd generate argument path so the test detects
broken flag names or bindings.

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Nitpick comments:
In `@cmd/crossplane/xrd/generate.go`:
- Around line 131-132: Expose a stable sentinel or typed existing-file error
from the Replace check in cmd/crossplane/xrd/generate.go lines 131-132, wrapping
it while retaining the file path and --replace guidance; update
cmd/crossplane/xrd/generate_test.go lines 773-827 to add want.err and reason
fields and compare errors with cmp.Diff and cmpopts.EquateErrors().

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 5c0300a5-cc9e-438a-bc2c-790218b0544b

📥 Commits

Reviewing files that changed from the base of the PR and between 7185390 and b1c20a4.

📒 Files selected for processing (2)

• cmd/crossplane/xrd/generate.go
• cmd/crossplane/xrd/generate_test.go