fix(common/load/streamToUnstructured): skip empty documents

[nkzk]

Description of your changes

Reimplementing crossplane/crossplane#7089.

The streamToUnstructured() function loads a stream of yaml into unstructured objects, and is used by different Loaders during beta validate.
If a yaml document in the stream only contains a comment, or the file is empty, this function will currently not fail, but add an empty object to the unstructured array, resulting in this warning during validation in resource validate: [!] could not find CRD/XRD for: /, Kind=

A simple example of where this might be an issue:

We generate the rendered resources that should be validated with a tool that wraps around crossplane render functionality.
Since we want the user to know that these files were generated, we add the following comment at the top:

# Generated by: x
# Do not edit this file manually
---
apiVersion: example.io/v1alpha1
kind: SomeResource
metadata:
  name: example
spec: {}
---
other resources...

But these comment results in the empty document issue when passing this file to the validate command.

Since this is valid yaml i believe the best thing is to fix what i believe is a logical issue in this function, instead of changing the generated file to accommodate.

I added a test and fix that ensures streamToUnstructured() skips empty objects like this.

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

Changes

Empty document handling

Layer / File(s)	Summary
Skip empty documents cmd/crossplane/common/load/loader.go, cmd/crossplane/common/load/loader_test.go	The loader ignores empty or comment-only YAML documents. The test verifies an empty non-nil resource slice without an error.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Suggested reviewers: adamwg

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Important

Pre-merge checks failed

Please resolve all errors before merging. Addressing warnings is optional.

❌ Failed checks (1 error)

Check name	Status	Explanation	Resolution
Breaking Changes	❌ Error	The cmd diff removes prior behavior by skipping empty YAML objects; the supplied PR metadata contains no 'breaking-change' label.	Add the 'breaking-change' label, or revise the change so empty documents retain the previous behavior.

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Feature Gate Requirement	✅ Passed	The PR changes only loader code and its unit test. It adds no apis/** changes or feature-gate implementation, and it fixes empty-document handling rather than adding an experimental feature.
Title check	✅ Passed	The title is descriptive, directly matches the change, and is 59 characters, below the 72-character limit.
Description check	✅ Passed	The description clearly explains the empty-document issue, the fix, its impact, and the added test.

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[coderabbitai]

🧹 Nitpick comments (1)

cmd/crossplane/common/load/loader_test.go (1)

489-497: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add a regression case for comment-only documents.

Thanks for covering empty byte documents. The PR objective also includes YAML documents that contain only comments. Add a table entry such as []byte("# comment only\n") and expect an empty non-nil resources slice with no error.

🤖 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/common/load/loader_test.go` around lines 489 - 497, Extend the
table-driven cases in the loader test around “SkipEmptyDocuments” with a
comment-only YAML stream such as []byte("# comment only\n"). Assert no error and
an empty, non-nil resources slice, matching the existing empty-byte document
expectations.

🤖 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.

Nitpick comments:
In `@cmd/crossplane/common/load/loader_test.go`:
- Around line 489-497: Extend the table-driven cases in the loader test around
“SkipEmptyDocuments” with a comment-only YAML stream such as []byte("# comment
only\n"). Assert no error and an empty, non-nil resources slice, matching the
existing empty-byte document expectations.

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ℹ️ Review info

⚙️ Run configuration

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Run ID: b8dc6e85-c7d7-46a1-9216-8dd2d4163d63

📥 Commits

Reviewing files that changed from the base of the PR and between 7185390 and 596f22b.

📒 Files selected for processing (2)

• cmd/crossplane/common/load/loader.go
• cmd/crossplane/common/load/loader_test.go