go/analysis: add -category=... filter flag to driver commands

go/analysis/checker/checker.go

@@ -343,6 +343,9 @@ func (act *Action) execOnce() {
 			if err := analysisinternal.ValidateFixes(act.Package.Fset, act.Analyzer, d.SuggestedFixes); err != nil {
 				panic(err)
 			}
+			if !analysisinternal.EnabledCategory(analysisflags.Category, d.Category) {
+				return
+			}
 			act.Diagnostics = append(act.Diagnostics, d)
 		},
 		ImportObjectFact:  act.ObjectFact,

go/analysis/internal/analysisflags/flags.go

@@ -24,8 +24,9 @@ import (
 
 // flags common to all {single,multi,unit}checkers.
 var (
-	JSON    = false // -json
-	Context = -1    // -c=N: if N>0, display offending line plus N lines of context
+	JSON     = false // -json
+	Context  = -1    // -c=N: if N>0, display offending line plus N lines of context
+	Category = ""    // -category=... comma-separated list of categories (may be negated with -)
 )
 
 // Parse creates a flag for each of the analyzer's flags,
@@ -74,6 +75,7 @@ func Parse(analyzers []*analysis.Analyzer, multi bool) []*analysis.Analyzer {
 	// flags common to all checkers
 	flag.BoolVar(&JSON, "json", JSON, "emit JSON output")
 	flag.IntVar(&Context, "c", Context, `display offending line with this many lines of context`)
+	flag.StringVar(&Category, "category", Category, "report only diagnostics of the specified categories (a comma-separated list); with a leading '-', discard diagnostics of the specified categories.")
 
 	// Add shims for legacy vet flags to enable existing
 	// scripts that run vet to continue to work.

go/analysis/unitchecker/unitchecker.go

@@ -385,6 +385,9 @@ func run(fset *token.FileSet, cfg *Config, analyzers []*analysis.Analyzer) ([]re
 						log.Println(err)
 						d.SuggestedFixes = nil
 					}
+					if !analysisinternal.EnabledCategory(analysisflags.Category, d.Category) {
+						return
+					}
 					act.diagnostics = append(act.diagnostics, d)
 				},
 				ImportObjectFact:  facts.ImportObjectFact,

gopls/doc/analyzers.md

@@ -505,6 +505,13 @@ following command:
 
 	$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...
 
+To apply a subset of modernization fixes, you can use the -category filter:
+
+	$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -category=efaceany,rangeint -test ./...
+
+A negated category list (e.g. "-category=-a,b") applies all fix categories
+except a and b.
+
 If the tool warns of conflicting fixes, you may need to run it more
 than once until it has applied all fixes cleanly. This command is
 not an officially supported interface and may change in the future.

gopls/internal/analysis/modernize/doc.go

@@ -38,6 +38,13 @@
 //
 //	$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...
 //
+// To apply a subset of modernization fixes, you can use the -category filter:
+//
+//	$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -category=efaceany,rangeint -test ./...
+//
+// A negated category list (e.g. "-category=-a,b") applies all fix categories
+// except a and b.
+//
 // If the tool warns of conflicting fixes, you may need to run it more
 // than once until it has applied all fixes cleanly. This command is
 // not an officially supported interface and may change in the future.

gopls/internal/doc/api.json

@@ -562,7 +562,7 @@
 						},
 						{
 							"Name": "\"modernize\"",
-							"Doc": "simplify code by using modern constructs\n\nThis analyzer reports opportunities for simplifying and clarifying\nexisting code by using more modern features of Go, such as:\n\n  - replacing an if/else conditional assignment by a call to the\n    built-in min or max functions added in go1.21;\n  - replacing sort.Slice(x, func(i, j int) bool) { return s[i] \u003c s[j] }\n    by a call to slices.Sort(s), added in go1.21;\n  - replacing interface{} by the 'any' type added in go1.18;\n  - replacing append([]T(nil), s...) by slices.Clone(s) or\n    slices.Concat(s), added in go1.21;\n  - replacing a loop around an m[k]=v map update by a call\n    to one of the Collect, Copy, Clone, or Insert functions\n    from the maps package, added in go1.21;\n  - replacing []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...),\n    added in go1.19;\n  - replacing uses of context.WithCancel in tests with t.Context, added in\n    go1.24;\n  - replacing omitempty by omitzero on structs, added in go1.24;\n  - replacing append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1),\n    added in go1.21\n  - replacing a 3-clause for i := 0; i \u003c n; i++ {} loop by\n    for i := range n {}, added in go1.22;\n  - replacing Split in \"for range strings.Split(...)\" by go1.24's\n    more efficient SplitSeq, or Fields with FieldSeq;\n\nTo apply all modernization fixes en masse, you can use the\nfollowing command:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...\n\nIf the tool warns of conflicting fixes, you may need to run it more\nthan once until it has applied all fixes cleanly. This command is\nnot an officially supported interface and may change in the future.",
+							"Doc": "simplify code by using modern constructs\n\nThis analyzer reports opportunities for simplifying and clarifying\nexisting code by using more modern features of Go, such as:\n\n  - replacing an if/else conditional assignment by a call to the\n    built-in min or max functions added in go1.21;\n  - replacing sort.Slice(x, func(i, j int) bool) { return s[i] \u003c s[j] }\n    by a call to slices.Sort(s), added in go1.21;\n  - replacing interface{} by the 'any' type added in go1.18;\n  - replacing append([]T(nil), s...) by slices.Clone(s) or\n    slices.Concat(s), added in go1.21;\n  - replacing a loop around an m[k]=v map update by a call\n    to one of the Collect, Copy, Clone, or Insert functions\n    from the maps package, added in go1.21;\n  - replacing []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...),\n    added in go1.19;\n  - replacing uses of context.WithCancel in tests with t.Context, added in\n    go1.24;\n  - replacing omitempty by omitzero on structs, added in go1.24;\n  - replacing append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1),\n    added in go1.21\n  - replacing a 3-clause for i := 0; i \u003c n; i++ {} loop by\n    for i := range n {}, added in go1.22;\n  - replacing Split in \"for range strings.Split(...)\" by go1.24's\n    more efficient SplitSeq, or Fields with FieldSeq;\n\nTo apply all modernization fixes en masse, you can use the\nfollowing command:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...\n\nTo apply a subset of modernization fixes, you can use the -category filter:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -category=efaceany,rangeint -test ./...\n\nA negated category list (e.g. \"-category=-a,b\") applies all fix categories\nexcept a and b.\n\nIf the tool warns of conflicting fixes, you may need to run it more\nthan once until it has applied all fixes cleanly. This command is\nnot an officially supported interface and may change in the future.",
 							"Default": "true",
 							"Status": ""
 						},
@@ -1338,7 +1338,7 @@
 		},
 		{
 			"Name": "modernize",
-			"Doc": "simplify code by using modern constructs\n\nThis analyzer reports opportunities for simplifying and clarifying\nexisting code by using more modern features of Go, such as:\n\n  - replacing an if/else conditional assignment by a call to the\n    built-in min or max functions added in go1.21;\n  - replacing sort.Slice(x, func(i, j int) bool) { return s[i] \u003c s[j] }\n    by a call to slices.Sort(s), added in go1.21;\n  - replacing interface{} by the 'any' type added in go1.18;\n  - replacing append([]T(nil), s...) by slices.Clone(s) or\n    slices.Concat(s), added in go1.21;\n  - replacing a loop around an m[k]=v map update by a call\n    to one of the Collect, Copy, Clone, or Insert functions\n    from the maps package, added in go1.21;\n  - replacing []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...),\n    added in go1.19;\n  - replacing uses of context.WithCancel in tests with t.Context, added in\n    go1.24;\n  - replacing omitempty by omitzero on structs, added in go1.24;\n  - replacing append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1),\n    added in go1.21\n  - replacing a 3-clause for i := 0; i \u003c n; i++ {} loop by\n    for i := range n {}, added in go1.22;\n  - replacing Split in \"for range strings.Split(...)\" by go1.24's\n    more efficient SplitSeq, or Fields with FieldSeq;\n\nTo apply all modernization fixes en masse, you can use the\nfollowing command:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...\n\nIf the tool warns of conflicting fixes, you may need to run it more\nthan once until it has applied all fixes cleanly. This command is\nnot an officially supported interface and may change in the future.",
+			"Doc": "simplify code by using modern constructs\n\nThis analyzer reports opportunities for simplifying and clarifying\nexisting code by using more modern features of Go, such as:\n\n  - replacing an if/else conditional assignment by a call to the\n    built-in min or max functions added in go1.21;\n  - replacing sort.Slice(x, func(i, j int) bool) { return s[i] \u003c s[j] }\n    by a call to slices.Sort(s), added in go1.21;\n  - replacing interface{} by the 'any' type added in go1.18;\n  - replacing append([]T(nil), s...) by slices.Clone(s) or\n    slices.Concat(s), added in go1.21;\n  - replacing a loop around an m[k]=v map update by a call\n    to one of the Collect, Copy, Clone, or Insert functions\n    from the maps package, added in go1.21;\n  - replacing []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...),\n    added in go1.19;\n  - replacing uses of context.WithCancel in tests with t.Context, added in\n    go1.24;\n  - replacing omitempty by omitzero on structs, added in go1.24;\n  - replacing append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1),\n    added in go1.21\n  - replacing a 3-clause for i := 0; i \u003c n; i++ {} loop by\n    for i := range n {}, added in go1.22;\n  - replacing Split in \"for range strings.Split(...)\" by go1.24's\n    more efficient SplitSeq, or Fields with FieldSeq;\n\nTo apply all modernization fixes en masse, you can use the\nfollowing command:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -test ./...\n\nTo apply a subset of modernization fixes, you can use the -category filter:\n\n\t$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -category=efaceany,rangeint -test ./...\n\nA negated category list (e.g. \"-category=-a,b\") applies all fix categories\nexcept a and b.\n\nIf the tool warns of conflicting fixes, you may need to run it more\nthan once until it has applied all fixes cleanly. This command is\nnot an officially supported interface and may change in the future.",
 			"URL": "https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize",
 			"Default": true
 		},

internal/analysisinternal/analysis.go

@@ -487,3 +487,20 @@ func CanImport(from, to string) bool {
 	}
 	return true
 }
+
+// EnabledCategory reports whether a given category is enabled by the specified
+// filter. filter is a comma-separated list of categories, optionally prefixed
+// with `-` to disable all provided categories. All categories are enabled with
+// an empty filter.
+func EnabledCategory(filter, category string) bool {
+	if filter == "" {
+		return true
+	}
+	// negation must be specified at the start
+	filter, exclude := strings.CutPrefix(filter, "-")
+	filters := strings.Split(filter, ",")
+	if slices.Contains(filters, category) {
+		return !exclude
+	}
+	return exclude
+}

internal/analysisinternal/analysis_test.go

@@ -32,3 +32,30 @@ func TestCanImport(t *testing.T) {
 		}
 	}
 }
+
+func TestEnabledCategory(t *testing.T) {
+	for _, tt := range []struct {
+		filter   string
+		category string
+		want     bool
+	}{
+		{"", "a", true},
+		{"a", "a", true},
+		{"-a", "a", false},
+		{"-b", "a", true},
+		{"b", "a", false},
+		{"a,b", "a", true},
+		{"a,b", "b", true},
+		{"-b,a", "a", false},
+		{"-b,a", "b", false},
+		{"a,-a", "a", true}, // negation must be at beginning
+		{"-b,c", "a", true},
+		{"b", "", false},
+		{"", "", true},
+	} {
+		got := EnabledCategory(tt.filter, tt.category)
+		if got != tt.want {
+			t.Errorf("EnabledCategory(%q,%q) = %v, want %v", tt.filter, tt.category, got, tt.want)
+		}
+	}
+}