refactor: drop dependency on github.com/fatih/structtag

[alexandear]

This PR drops one dependency.
Because https://github.com/fatih/structtag seems unmaintained, and we do not utilize all the functions from the library. We need only Parse.

Our implementation is a little bit faster:

❯ go test -bench . -benchmem -count=1 -run=^$ ./internal/structtag/...
goos: darwin
goarch: arm64
pkg: github.com/mgechev/revive/internal/structtag
cpu: Apple M4 Pro
BenchmarkParseCompare/single/revive-12          23213113                51.08 ns/op           88 B/op          3 allocs/op
BenchmarkParseCompare/single/fatih-12           18595112                68.07 ns/op          112 B/op          4 allocs/op
BenchmarkParseCompare/with_options/revive-12    16504845                72.00 ns/op          120 B/op          3 allocs/op
BenchmarkParseCompare/with_options/fatih-12     13443501                87.82 ns/op          144 B/op          4 allocs/op
BenchmarkParseCompare/multiple/revive-12         7166770               165.9 ns/op           296 B/op          7 allocs/op
BenchmarkParseCompare/multiple/fatih-12          6108170               195.6 ns/op           352 B/op         10 allocs/op
BenchmarkParseCompare/complex/revive-12          5118066               232.5 ns/op           432 B/op          9 allocs/op
BenchmarkParseCompare/complex/fatih-12           4201783               269.2 ns/op           480 B/op         12 allocs/op
PASS

bench_test.go

package structtag_test

import (
	"testing"

	fatihst "github.com/fatih/structtag"

	"github.com/mgechev/revive/internal/structtag"
)

func BenchmarkParseCompare(b *testing.B) {
	tests := []struct {
		name string
		tag  string
	}{
		{
			name: "single",
			tag:  `json:"foo"`,
		},
		{
			name: "with_options",
			tag:  `json:"foo,omitempty,string"`,
		},
		{
			name: "multiple",
			tag:  `json:"foo,omitempty" xml:"bar" db:"baz,primarykey"`,
		},
		{
			name: "complex",
			tag:  `json:"id,omitempty,string" xml:"id,attr" db:"id,primarykey" validate:"required,uuid4"`,
		},
	}

	for _, tt := range tests {
		b.Run(tt.name+"/revive", func(b *testing.B) {
			for b.Loop() {
				_, _ = structtag.Parse(tt.tag)
			}
		})
		b.Run(tt.name+"/fatih", func(b *testing.B) {
			for b.Loop() {
				_, _ = fatihst.Parse(tt.tag)
			}
		})
	}
}

Inspired by https://cs.opensource.google/go/x/tools/+/refs/tags/v0.42.0:go/analysis/passes/structtag/structtag.go

[Copilot]

Pull request overview

This PR removes the dependency on github.com/fatih/structtag by introducing an internal internal/structtag package that implements the needed struct-tag parsing functionality, and updates the struct-tag rule to use it.

Changes:

• Added internal/structtag with a Parse function and Tag helpers (Value, String).
• Updated rule/struct_tag.go to use the new internal parser.
• Removed github.com/fatih/structtag from go.mod/go.sum and added tests for the new parser.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
rule/struct_tag.go	Switches the struct-tag rule to the new internal parser API.
internal/structtag/structtag.go	New internal struct tag parser and Tag implementation.
internal/structtag/structtag_test.go	New unit tests validating parsing and Tag.Value().
go.mod	Drops the github.com/fatih/structtag dependency.
go.sum	Removes checksums for the dropped dependency.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

[denisvmedia]

LGTM, with a couple of nit comments