fix: consider path prefix when matching path patterns

[pohly]

Problem

When someone invokes golangci-lint in a sub-directory, they can set the path prefix to make the output look like the invocation had been done in the root.
But this prefix was ignored when checking path patterns of exclude, severity, and skip files/dirs entries, so those with matching for directories only worked when golangci-lint was always invoked in the same directory.

Solution

The underlying problem is that the rules from the configuration get checked before updating the path associated with the issues in the path fixer.
To make the prefix work, it now gets passed down into processors and added there to the issue path before checking against the path pattern.

For exclude and severity rules, this could have been done through a separate parameter, but bundling it in a new fsutils helper struct made the change a bit smaller.

[boring-cyborg]

Hey, thank you for opening your first Pull Request !

[CLAassistant]

All committers have signed the CLA.

[pohly]

@ldez: I also looked at skip-files and skip-dirs. Both had the same problem, so I extended the PR to also fix those.

I think this is ready for review now.

[pohly]

In case someone wonders: the reason why the directory has to be changed in the Kubernetes repo is that staging/src/k8s.io/* are all separate modules, so golangci-lint ./staging/src/k8s.io/... wouldn't work. But we want to maintain a single golangci.yaml for all modules with path matches for certain directories, hence this PR...

[pohly]

The path prefixer test failed on Windows because I was using "path.Join", not "path/filepath.Join" as before. This change should fix that:

diff --git a/pkg/fsutils/files.go b/pkg/fsutils/files.go
index 542af531..3d369a23 100644
--- a/pkg/fsutils/files.go
+++ b/pkg/fsutils/files.go
@@ -1,6 +1,6 @@
 package fsutils
 
-import "path"
+import "path/filepath"
 
 // Files combines different operations related to handling file paths and
 // content.
@@ -32,5 +32,5 @@ func WithPathPrefix(pathPrefix, relativePath string) string {
        if pathPrefix == "" {
                return relativePath
        }
-       return path.Join(pathPrefix, relativePath)
+       return filepath.Join(pathPrefix, relativePath)
 }

[ldez]

I think your approach can be extended to the Fixer processor, can try to fix the Fixer?

[pohly]

I think your approach can be extended to the Fixer processor, can try to fix the Fixer?

The problem with the fixer processor seems to be that it runs after the path prefixer (#3626).

That leads to the inverse problem of what I am solving here: the fixer sees the path with prefix which doesn't match the correct path relative to the current working directory, whereas severity and exclude processors (before this PR) see the path without the prefix when they need it with prefix.

The fix for the fixer in the PR above is to strip the prefix again. That doesn't seem ideal. Perhaps a simpler solution is to move the path prefixing and sorting out of the normal set of processors and do that after fixing?

Either way, such a fix doesn't need to be in this PR.

Thanks for the comment fixes, I included all of them in this commit - I prefer to keep the commit history clean. Let me know if you prefer it otherwise and I can restore them as a separate commit.

[ldez]

Thanks for the comment fixes, I included all of them in this commit - I prefer to keep the commit history clean. Let me know if you prefer it otherwise and I can restore them as a separate commit.

I prefer to have fixes as commits, it's easier to follow the review.

[pohly]

Okay, I added the second commit with the comment changes.

BTW, should I also rebase each time I do a push to avoid having to merge with master?

[pohly]

I prepared a separate PR with my idea of fixing the fixer. It's unrelated to the changes in this PR, but there will be a slight merge conflict.

I can also add those other changes here, if you prefer a single PR.

[ldez]

LTGM