fix: Allow patches with empty files with multiple newlines or comments

[jchanam]

Fixes #5487

Right now, when a file is empty, the patches given by the resmap (sm patches) or the jsonpatch is nil. When the file has only comments in it (virtually empty if we think about changes to be made) or multiple newlines, the result given by said functions is an empty slice.

I've changed the check for when we can't allow to have a patch that is valid for both SM and JSON, so it allows empty changes (both nil or empty slices).

Extra comments:

• I think that it'd be better to change the functions and return a nil object, instead of an empty slice, but I'm unsure on where to do those changes.
• Also, I can't make the tests to run locally as they complain for the content file to be empty, and that should not be the case as it's perfectly ok for the built binary to use empty patches.

I'll be more than happy to work on these two with some help or guidance.

[k8s-ci-robot]

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[jchanam]

Hi @stormqueen1990 @varshaprasad96,

Could I get some help in getting this approved?

Thank you!

[stormqueen1990]

Hi @stormqueen1990 @varshaprasad96,

Could I get some help in getting this approved?

Thank you!

Hi there, @jchanam!

I am taking a look at this and got a bit confused with the comment you made in the PR description about the tests. Do you mean that tests are currently failing locally?

[stormqueen1990]

/test all

[jchanam]

Hi @stormqueen1990 ,

Yes, I meant that. It looks like there are a test checking if the input is not empty, but the goal of my code is testing specifically that, as it should not fail. If we add a file to kustomize that is empty, it should simply not produce any output, instead of failing.

Also, now the tests here say that there's a diff found on the file I've modified. How can I fix that or change extra code so the tests continue?

Thank you!

[jchanam]

@stormqueen1990 This is an example of what I mean.

Here I'm testing the input to be a file with only a new line. Based on my new code, this should give no error, but I'm getting a specific error from the tests extra code saying that the input to RunTransformerAndCheckError can't be empty.

[stormqueen1990]

You're missing a go generate step for this code. The plugin/builtin/patchtransformer/PatchTransformer.go file you updated is a scaffold for the plugin generated under api/internal/builtins/PatchTransformer.go; therefore, you will need to run go generate plugin/builtin/patchtransformer/PatchTransformer.go to update the final built-in plugin code.

You can also run the prow checks locally using make prow-presubmit-check from the root of the repository.

[jchanam]

Thank you so much @stormqueen1990

I've just generated the plugin and pushed the change.

Regarding the test, I run them locally, but I'm given an error that IMO shouldn't happen, as it's complaining of exactly what I want to test:

2024/11/19 15:09:31 compiler created: /Users/juliochana/github/kustomize/plugin/builtin/patchtransformer/PatchTransformer.so
    harnessenhanced.go:219: config: '
        '
    harnessenhanced.go:220: Err: expected 1 resource, found 0 in [10]
--- FAIL: TestPatchTransformerPatchEmpty (0.71s)
=== RUN   TestPatchTransformerPatchEmptyOnlyComments
2024/11/19 15:09:32 compiler created: /Users/juliochana/github/kustomize/plugin/builtin/patchtransformer/PatchTransformer.so
    harnessenhanced.go:219: config: '
        # File with only comments

        # Is a virtually empty yaml
        '
    harnessenhanced.go:220: Err: expected 1 resource, found 0 in [10 35 32 70 105 108 101 32 119 105 116 104 32 111 110 108 121 32 99 111 109 109 101 110 116 115 10 10 35 32 73 115 32 97 32 118 105 114 116 117 97 108 108 121 32 101 109 112 116 121 32 121 97 109 108 10]
--- FAIL: TestPatchTransformerPatchEmptyOnlyComments (0.68s)
FAIL
FAIL	command-line-arguments	17.627s
FAIL
**** FAILURE in ./plugin/builtin/patchtransformer

I'm adding an "empty file" (for kustomize) and with my change, it should work. Could you help me improving this testing scaffolding so it stops complaining about the empty file?

[stormqueen1990]

Hi there, @jchanam! Sorry for the delay in responding. Let me take a look at this and I'll get back to you!

[stormqueen1990]

Hi again, @jchanam!

I took a deeper look and this test case isn't quite right. If you copy it and paste in a Kustomize version without the regression (e.g. tag kustomize/v5.1.1) it still won't pass.

Taking a look at the configuration for RunTransformerAndCheckError, the first argument of the function refers to the transformer configuration and that cannot be empty under any circumstance:

kustomize/api/testutils/kusttest/harnessenhanced.go

Lines 200 to 204 in 7911b2c

	func (th *HarnessEnhanced) RunTransformerAndCheckError(
	config, input string, assertFn AssertFunc) {
	_, err := th.RunTransformer(config, input)
	assertFn(th.t, err)
	}

The transformer configuration is the blurb that instructs Kustomize how to deal with a patch. In the PatchTransformer case, that would be this part of the kustomization.yaml file:

patches:
  - target:
      group: apps
      version: v1
      kind: Deployment
      name: test-deployment
    path: patches/test-patch.yaml

What we want to be empty in this scenario is the patch, i.e. the file to which the transformer configuration refers, not the transformer configuration. The tests that write patch files in this test file are more similar to the scenario you need to emulate (for example, TestPatchTransformerSmpSidecars).

[stormqueen1990]

/test all

[k8s-ci-robot]

@jchanam: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
kustomize-presubmit-master	bfd408c	link	true	/test kustomize-presubmit-master

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[jchanam]

@stormqueen1990 Sorry for the late response. I think I was able to follow your guidance and fix the tests.

[jchanam]

/retest

[k8s-ci-robot]

@jchanam: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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