internal/lsp/analysis: add simplify-range pass from "gofmt -s"
This is one of the simplifications that "gofmt -s" applies.
https://golang.org/cmd/gofmt/#hdr-The_simplify_command
A range of the form:
for x, _ = range v {...}
will be simplified to:
for x = range v {...}
A range of the form:
for _ = range v {...}
will be simplified to:
for range v {...}
Updates golang/go#37221
Change-Id: Ic6babbd0b8ab961ebb4d0d6df72df52d9acde6e7
Reviewed-on: https://go-review.googlesource.com/c/tools/+/223661
Run-TryBot: Rohan Challa <rohan@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
diff --git a/gopls/doc/analyzers.md b/gopls/doc/analyzers.md
index f5dd846..77bc4a8 100644
--- a/gopls/doc/analyzers.md
+++ b/gopls/doc/analyzers.md
@@ -321,6 +321,32 @@
Default value: `true`.
+### **simplifyrange**
+
+check for range statement simplifications
+
+A range of the form:
+```go
+for x, _ = range v {...}
+```
+will be simplified to:
+```go
+for x = range v {...}
+```
+
+A range of the form:
+```go
+for _ = range v {...}
+```
+will be simplified to:
+```go
+for range v {...}
+```
+
+This is one of the simplifications that "gofmt -s" applies.
+
+Default value: `true`.
+
### **sortslice**
check the argument type of sort.Slice
diff --git a/internal/lsp/analysis/simplifyrange/simplifyrange.go b/internal/lsp/analysis/simplifyrange/simplifyrange.go
new file mode 100644
index 0000000..e53f50d
--- /dev/null
+++ b/internal/lsp/analysis/simplifyrange/simplifyrange.go
@@ -0,0 +1,114 @@
+// Copyright 2020 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.
+
+// Package simplifyrange defines an Analyzer that simplifies range statements.
+// https://golang.org/cmd/gofmt/#hdr-The_simplify_command
+// https://github.com/golang/go/blob/master/src/cmd/gofmt/simplify.go
+package simplifyrange
+
+import (
+ "bytes"
+ "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"
+)
+
+const Doc = `check for range statement simplifications
+
+A range of the form:
+ for x, _ = range v {...}
+will be simplified to:
+ for x = range v {...}
+
+A range of the form:
+ for _ = range v {...}
+will be simplified to:
+ for range v {...}
+
+This is one of the simplifications that "gofmt -s" applies.`
+
+var Analyzer = &analysis.Analyzer{
+ Name: "simplifyrange",
+ Doc: Doc,
+ Requires: []*analysis.Analyzer{inspect.Analyzer},
+ Run: run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+ inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+ nodeFilter := []ast.Node{
+ (*ast.RangeStmt)(nil),
+ }
+ inspect.Preorder(nodeFilter, func(n ast.Node) {
+ stmt := n.(*ast.RangeStmt)
+ end := newlineIndex(pass.Fset, stmt)
+ var old ast.Expr
+ // Range statements of the form: for i, _ := range x {}
+ if isBlank(stmt.Value) {
+ old = stmt.Value
+ defer func() {
+ stmt.Value = old
+ }()
+ stmt.Value = nil
+ }
+ // Range statements of the form: for _ := range x {}
+ if isBlank(stmt.Key) && stmt.Value == nil {
+ old = stmt.Key
+ defer func() {
+ stmt.Key = old
+ }()
+ stmt.Key = nil
+ }
+ // Return early if neither if condition is met.
+ if old == nil {
+ return
+ }
+ pass.Report(analysis.Diagnostic{
+ Pos: old.Pos(),
+ End: old.End(),
+ Message: "simplify range expression",
+ SuggestedFixes: suggestedFixes(pass.Fset, stmt, end),
+ })
+ })
+ return nil, nil
+}
+
+func suggestedFixes(fset *token.FileSet, rng *ast.RangeStmt, end token.Pos) []analysis.SuggestedFix {
+ var b bytes.Buffer
+ printer.Fprint(&b, fset, rng)
+ stmt := b.Bytes()
+ index := bytes.Index(stmt, []byte("\n"))
+ // If there is a new line character, then don't replace the body.
+ if index != -1 {
+ stmt = stmt[:index]
+ }
+ return []analysis.SuggestedFix{{
+ Message: "Remove empty value",
+ TextEdits: []analysis.TextEdit{{
+ Pos: rng.Pos(),
+ End: end,
+ NewText: stmt[:index],
+ }},
+ }}
+}
+
+func newlineIndex(fset *token.FileSet, rng *ast.RangeStmt) token.Pos {
+ var b bytes.Buffer
+ printer.Fprint(&b, fset, rng)
+ contents := b.Bytes()
+ index := bytes.Index(contents, []byte("\n"))
+ if index == -1 {
+ return rng.End()
+ }
+ return rng.Pos() + token.Pos(index)
+}
+
+func isBlank(x ast.Expr) bool {
+ ident, ok := x.(*ast.Ident)
+ return ok && ident.Name == "_"
+}
diff --git a/internal/lsp/analysis/simplifyrange/simplifyrange_test.go b/internal/lsp/analysis/simplifyrange/simplifyrange_test.go
new file mode 100644
index 0000000..ecc7a96
--- /dev/null
+++ b/internal/lsp/analysis/simplifyrange/simplifyrange_test.go
@@ -0,0 +1,17 @@
+// Copyright 2020 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.
+
+package simplifyrange_test
+
+import (
+ "testing"
+
+ "golang.org/x/tools/go/analysis/analysistest"
+ "golang.org/x/tools/internal/lsp/analysis/simplifyrange"
+)
+
+func Test(t *testing.T) {
+ testdata := analysistest.TestData()
+ analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "a")
+}
diff --git a/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go b/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go
new file mode 100644
index 0000000..49face1
--- /dev/null
+++ b/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go
@@ -0,0 +1,16 @@
+// Copyright 2020 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.
+
+package testdata
+
+import "log"
+
+func m() {
+ maps := make(map[string]string)
+ for k, _ := range maps { // want "simplify range expression"
+ log.Println(k)
+ }
+ for _ = range maps { // want "simplify range expression"
+ }
+}
diff --git a/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go.golden b/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go.golden
new file mode 100644
index 0000000..ec8490a
--- /dev/null
+++ b/internal/lsp/analysis/simplifyrange/testdata/src/a/a.go.golden
@@ -0,0 +1,16 @@
+// Copyright 2020 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.
+
+package testdata
+
+import "log"
+
+func m() {
+ maps := make(map[string]string)
+ for k := range maps { // want "simplify range expression"
+ log.Println(k)
+ }
+ for range maps { // want "simplify range expression"
+ }
+}
diff --git a/internal/lsp/source/options.go b/internal/lsp/source/options.go
index b70b3ba..363f426 100644
--- a/internal/lsp/source/options.go
+++ b/internal/lsp/source/options.go
@@ -36,6 +36,7 @@
"golang.org/x/tools/go/analysis/passes/unreachable"
"golang.org/x/tools/go/analysis/passes/unsafeptr"
"golang.org/x/tools/go/analysis/passes/unusedresult"
+ "golang.org/x/tools/internal/lsp/analysis/simplifyrange"
"golang.org/x/tools/internal/lsp/debug/tag"
"golang.org/x/tools/internal/lsp/diff"
"golang.org/x/tools/internal/lsp/diff/myers"
@@ -511,5 +512,6 @@
testinggoroutine.Analyzer.Name: {Analyzer: testinggoroutine.Analyzer, Enabled: true},
// gofmt -s suite:
+ simplifyrange.Analyzer.Name: {Analyzer: simplifyrange.Analyzer, Enabled: true, HighConfidence: true},
}
}
