Add new linter canonicalheader

[lasiar]

canonicalheader analyzes code and reports or fixes non-canonical header key in net/http.Header, doc.

The linter suggest canonical header:

http.Header{}.Get("Test-Header")

instead of non-canonical header:

http.Header{}.Get("TeSt-HeAdEr")

This change also speeds up the code a little, benchmark from repo:

name             time/op
Canonical-10     29.7ns ± 4%
NonCanonical-10  69.0ns ± 1%

name             alloc/op
Canonical-10      0.00B     
NonCanonical-10   16.0B ± 0%

name             allocs/op
Canonical-10       0.00     
NonCanonical-10    1.00 ± 0%

Now, the linter works only with value net/http.Header (not pointer) and with string literal.

[CLAassistant]

All committers have signed the CLA.

[ldez]

In order for a pull request adding a linter to be reviewed, the linter and the PR must follow some requirements.

• The CLA must be signed

Pull Request Description

• It must have a link to the linter repository.
• It must provide a short description of the linter.

Linter

• It must not be a duplicate of another linter or a rule of a linter. (the team will help to verify that)
• It must have a valid license (AGPL is not allowed) and the file must contain the required information by the license, ex: author, year, etc.
• The linter repository must have a CI and tests.
• It must use go/analysis.
• It must have a valid tag, ex: v1.0.0, v0.1.0.
• It must not contain init().
• It must not contain panic().
• It must not contain log.fatal(), os.exit(), or similar.
• It must not modify the AST.
• It must not have false positives/negatives. (the team will help to verify that)
• It must have tests inside golangci-lint.

The Linter Tests Inside Golangci-lint

• They must have at least one std lib import.
• They must work with T=<name of the linter test file>.go make test_linters. (the team will help to verify that)

.golangci.reference.yml

• The linter must be added to the list of available linters (alphabetical case-insensitive order).
  • enable and disable options
• If the linter has a configuration, the exhaustive configuration of the linter must be added (alphabetical case-insensitive order)
  • The values must be different from the default ones.
  • The default values must be defined in a comment.
  • The option must have a short description.

Others Requirements

• The files (tests and linter) inside golangci-lint must have the same name as the linter.
• The .golangci.yml of golangci-lint itself must not be edited and the linter must not be added to this file.
• The linters must be sorted in the alphabetical order (case-insensitive) in the Manager.GetAllSupportedLinterConfigs(...) and .golangci.reference.yml.
• The load mode (WithLoadMode(...)):
  • if the linter doesn't use types: goanalysis.LoadModeSyntax
  • goanalysis.LoadModeTypesInfo required WithLoadForGoAnalysis() in the Manager.GetAllSupportedLinterConfigs(...)
• The version in WithSince(...) must be the next minor version (v1.X.0) of golangci-lint.
• WithURL() must contain the URL of the repository.

Recommendations

• The linter should not use SSA. (SSA can be a problem with generics)
• The linter repository should have a readme and linting.
• The linter should be published as a binary. (useful to diagnose bug origins)

---

The golangci-lint team will edit this comment to check the boxes before and during the review.

The code review will start after the completion of those checkboxes (except for the specific items that the team will help to verify).

If the author of the PR is a member of the golangci-lint team, he should not edit this message.

This checklist does not imply that we will accept the linter.

[alexandear]

Staticcheck linter has SA1008 check reporting non-canonical headers. Could you please explain what are the differences between canonicalheader and staticcheck's SA1008?

[lasiar]

Staticcheck linter has SA1008 check reporting non-canonical headers. Could you please explain what are the differences between canonicalheader and staticcheck's SA1008?

Yes, you are right.

Thank you for research, these SA1008 can't report about wrote with methods to Headers, I will create PR in staticcheck.

I close this PR.

[ccoVeille]

Staticcheck linter has SA1008 check reporting non-canonical headers. Could you please explain what are the differences between canonicalheader and staticcheck's SA1008?

Yes, you are right.

Thank you for research, these SA1008 can't report about wrote with methods to Headers, I will create PR in staticcheck.

Here is the issue that was raised by @lasiar on staticcheck dominikh/go-tools#1519 (comment)

They declined enforcing it at staticcheck level.

[ldez]

#4672