gopls/internal/analysis: add skipped analysis simplify on generated code

On generated code, gopls always suggest to simplify code produced literals polluting the "Problems" pane in IDE, while properly refusing to format file on save because it is generated code.

This change will make simplifycompositelit, simplifyrange, simplifyslice skipped on generated code, so it will not polluting the "Problems" pane in IDE.

Fixes golang/go#67733

Change-Id: I99b3f083ce96594f360576f530cfc7f4b77c1cc1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/598835
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>

gopls/doc/analyzers.md

@@ -636,6 +636,8 @@ will be simplified to:
 
 This is one of the simplifications that "gofmt -s" applies.
 
+This analyzer ignores generated code.
+
 Default: on.
 
 Package documentation: [simplifycompositelit](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifycompositelit)
@@ -662,6 +664,8 @@ will be simplified to:
 
 This is one of the simplifications that "gofmt -s" applies.
 
+This analyzer ignores generated code.
+
 Default: on.
 
 Package documentation: [simplifyrange](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifyrange)
@@ -680,6 +684,8 @@ will be simplified to:
 
 This is one of the simplifications that "gofmt -s" applies.
 
+This analyzer ignores generated code.
+
 Default: on.
 
 Package documentation: [simplifyslice](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifyslice)

gopls/internal/analysis/simplifycompositelit/doc.go

@@ -19,4 +19,6 @@
 //	[]T{{}, {}}
 //
 // This is one of the simplifications that "gofmt -s" applies.
+//
+// This analyzer ignores generated code.
 package simplifycompositelit

gopls/internal/analysis/simplifycompositelit/simplifycompositelit.go

@@ -19,6 +19,7 @@ import (
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
 	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/gopls/internal/util/astutil"
 	"golang.org/x/tools/internal/analysisinternal"
 )
 
@@ -34,9 +35,21 @@ var Analyzer = &analysis.Analyzer{
 }
 
 func run(pass *analysis.Pass) (interface{}, error) {
+	// Gather information whether file is generated or not
+	generated := make(map[*token.File]bool)
+	for _, file := range pass.Files {
+		if astutil.IsGenerated(file) {
+			generated[pass.Fset.File(file.Pos())] = true
+		}
+	}
+
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	nodeFilter := []ast.Node{(*ast.CompositeLit)(nil)}
 	inspect.Preorder(nodeFilter, func(n ast.Node) {
+		if _, ok := generated[pass.Fset.File(n.Pos())]; ok {
+			return // skip checking if it's generated code
+		}
+
 		expr := n.(*ast.CompositeLit)
 
 		outer := expr

gopls/internal/analysis/simplifycompositelit/simplifycompositelit_test.go

@@ -13,5 +13,5 @@ import (
 
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
-	analysistest.RunWithSuggestedFixes(t, testdata, simplifycompositelit.Analyzer, "a")
+	analysistest.RunWithSuggestedFixes(t, testdata, simplifycompositelit.Analyzer, "a", "generatedcode")
 }

gopls/internal/analysis/simplifycompositelit/testdata/src/generatedcode/generatedcode.go.golden

@@ -0,0 +1,17 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated with somegen DO NOT EDIT.
+
+package testdata
+
+type T struct {
+	x, y int
+}
+
+var _ = [42]T{
+	T{}, // No simplification fix is offered in generated code.
+	T{1, 2}, // No simplification fix is offered in generated code.
+	T{3, 4}, // No simplification fix is offered in generated code.
+}

gopls/internal/analysis/simplifyrange/doc.go

@@ -27,4 +27,6 @@
 //	for range v {...}
 //
 // This is one of the simplifications that "gofmt -s" applies.
+//
+// This analyzer ignores generated code.
 package simplifyrange

gopls/internal/analysis/simplifyrange/simplifyrange.go

@@ -14,6 +14,7 @@ import (
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
 	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/gopls/internal/util/astutil"
 	"golang.org/x/tools/internal/analysisinternal"
 )
 
@@ -29,11 +30,23 @@ var Analyzer = &analysis.Analyzer{
 }
 
 func run(pass *analysis.Pass) (interface{}, error) {
+	// Gather information whether file is generated or not
+	generated := make(map[*token.File]bool)
+	for _, file := range pass.Files {
+		if astutil.IsGenerated(file) {
+			generated[pass.Fset.File(file.Pos())] = true
+		}
+	}
+
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	nodeFilter := []ast.Node{
 		(*ast.RangeStmt)(nil),
 	}
 	inspect.Preorder(nodeFilter, func(n ast.Node) {
+		if _, ok := generated[pass.Fset.File(n.Pos())]; ok {
+			return // skip checking if it's generated code
+		}
+
 		var copy *ast.RangeStmt // shallow-copy the AST before modifying
 		{
 			x := *n.(*ast.RangeStmt)

gopls/internal/analysis/simplifyrange/simplifyrange_test.go

@@ -15,7 +15,7 @@ import (
 
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
-	analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "a")
+	analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "a", "generatedcode")
 	if slices.Contains(build.Default.ReleaseTags, "go1.23") { // uses iter.Seq
 		analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "rangeoverfunc")
 	}

gopls/internal/analysis/simplifyrange/testdata/src/generatedcode/generatedcode.go.golden

@@ -0,0 +1,18 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated with somegen DO NOT EDIT.
+
+package testdata
+
+import "log"
+
+func mgeneratedcode() {
+	maps := make(map[string]string)
+	for k, _ := range maps { // No simplification fix is offered in generated code.
+		log.Println(k)
+	}
+	for _ = range maps { // No simplification fix is offered in generated code.
+	}
+}

gopls/internal/analysis/simplifyslice/doc.go

@@ -19,4 +19,6 @@
 //	s[a:]
 //
 // This is one of the simplifications that "gofmt -s" applies.
+//
+// This analyzer ignores generated code.
 package simplifyslice

gopls/internal/analysis/simplifyslice/simplifyslice.go

@@ -10,10 +10,12 @@ import (
 	"fmt"
 	"go/ast"
 	"go/printer"
+	"go/token"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
 	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/gopls/internal/util/astutil"
 	"golang.org/x/tools/internal/analysisinternal"
 )
 
@@ -37,11 +39,23 @@ var Analyzer = &analysis.Analyzer{
 //       x, y := b[:n], b[n:]
 
 func run(pass *analysis.Pass) (interface{}, error) {
+	// Gather information whether file is generated or not
+	generated := make(map[*token.File]bool)
+	for _, file := range pass.Files {
+		if astutil.IsGenerated(file) {
+			generated[pass.Fset.File(file.Pos())] = true
+		}
+	}
+
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	nodeFilter := []ast.Node{
 		(*ast.SliceExpr)(nil),
 	}
 	inspect.Preorder(nodeFilter, func(n ast.Node) {
+		if _, ok := generated[pass.Fset.File(n.Pos())]; ok {
+			return // skip checking if it's generated code
+		}
+
 		expr := n.(*ast.SliceExpr)
 		// - 3-index slices always require the 2nd and 3rd index
 		if expr.Max != nil {

gopls/internal/analysis/simplifyslice/simplifyslice_test.go

@@ -13,5 +13,5 @@ import (
 
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
-	analysistest.RunWithSuggestedFixes(t, testdata, simplifyslice.Analyzer, "a", "typeparams")
+	analysistest.RunWithSuggestedFixes(t, testdata, simplifyslice.Analyzer, "a", "generatedcode", "typeparams")
 }

gopls/internal/analysis/simplifyslice/testdata/src/generatedcode/generatedcode.go.golden

@@ -0,0 +1,72 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated with somegen DO NOT EDIT.
+
+package testdata
+
+var (
+	a [10]byte
+	b [20]float32
+	s []int
+	t struct {
+		s []byte
+	}
+
+	_ = a[0:]
+	_ = a[1:10]
+	_ = a[2:len(a)] // No simplification fix is offered in generated code.
+	_ = a[3:(len(a))]
+	_ = a[len(a)-1 : len(a)] // No simplification fix is offered in generated code.
+	_ = a[2:len(a):len(a)]
+
+	_ = a[:]
+	_ = a[:10]
+	_ = a[:len(a)] // No simplification fix is offered in generated code.
+	_ = a[:(len(a))]
+	_ = a[:len(a)-1]
+	_ = a[:len(a):len(a)]
+
+	_ = s[0:]
+	_ = s[1:10]
+	_ = s[2:len(s)] // No simplification fix is offered in generated code.
+	_ = s[3:(len(s))]
+	_ = s[len(a) : len(s)-1]
+	_ = s[0:len(b)]
+	_ = s[2:len(s):len(s)]
+
+	_ = s[:]
+	_ = s[:10]
+	_ = s[:len(s)] // No simplification fix is offered in generated code.
+	_ = s[:(len(s))]
+	_ = s[:len(s)-1]
+	_ = s[:len(b)]
+	_ = s[:len(s):len(s)]
+
+	_ = t.s[0:]
+	_ = t.s[1:10]
+	_ = t.s[2:len(t.s)]
+	_ = t.s[3:(len(t.s))]
+	_ = t.s[len(a) : len(t.s)-1]
+	_ = t.s[0:len(b)]
+	_ = t.s[2:len(t.s):len(t.s)]
+
+	_ = t.s[:]
+	_ = t.s[:10]
+	_ = t.s[:len(t.s)]
+	_ = t.s[:(len(t.s))]
+	_ = t.s[:len(t.s)-1]
+	_ = t.s[:len(b)]
+	_ = t.s[:len(t.s):len(t.s)]
+)
+
+func _() {
+	s := s[0:len(s)] // No simplification fix is offered in generated code.
+	_ = s
+}
+
+func m() {
+	maps := []int{}
+	_ = maps[1:len(maps)] // No simplification fix is offered in generated code.
+}