internal/analysisinternal: extra new line when add first std import

xieyuschen · gopherbot · commit af2d2d6b384d · 2025-09-10T17:49:38.000-07:00
AddImport now insert a std import at the first place of import group and it's consecutive with the next import. When the next consecutive import is 3rd package import, after applying edits when running 'modernizer -fix ...', go/format.Source is used to format it, which sorts consecutive imports by string comparing. As a result, when slicescontains modernizer adds std 'slices' import, it is adjcent with 3rd package import and sorted at the last place. This CL changes analysisinternal.AddImport behavior by adding an extra newline character when inserting std package to a group without any std import to ensure std and 3rd imports won't be consecutive. Fixes: golang/go#75296 Change-Id: I22b143b87bf901502c53a42e0363ed624ae4542e Reviewed-on: https://go-review.googlesource.com/c/tools/+/702335 Reviewed-by: Michael Pratt <mpratt@google.com> Auto-Submit: Alan Donovan <adonovan@google.com> Reviewed-by: Alan Donovan <adonovan@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/internal/analysisinternal/addimport_test.go b/internal/analysisinternal/addimport_test.go
@@ -291,6 +291,31 @@ import "io"
 
 import "vendor/golang.org/x/net/dns/dnsmessage"
 
+func _(io.Reader) {
+	fmt
+}`,
+		},
+		{
+			descr: descr("add import to group without std import"),
+			src: `package a
+
+import (
+	"golang.org/x/tools/go/packages"
+	gossa "golang.org/x/tools/go/ssa"
+)
+
+func _(io.Reader) {
+	«fmt fmt»
+}`,
+			want: `package a
+
+import (
+	"fmt"
+
+	"golang.org/x/tools/go/packages"
+	gossa "golang.org/x/tools/go/ssa"
+)
+
 func _(io.Reader) {
 	fmt
 }`,
diff --git a/internal/analysisinternal/analysis.go b/internal/analysisinternal/analysis.go
@@ -277,19 +277,27 @@ func AddImport(info *types.Info, file *ast.File, preferredName, pkgpath, member
 			before = decl0.Doc
 		}
 	}
-	// If the first decl is an import group, add this new import at the end.
 	if gd, ok := before.(*ast.GenDecl); ok && gd.Tok == token.IMPORT && gd.Rparen.IsValid() {
-		pos = gd.Rparen
-		// if it's a std lib, we should append it at the beginning of import group.
-		// otherwise we may see the std package is put at the last behind a 3rd module which doesn't follow our convention.
-		// besides, gofmt doesn't help in this case.
-		if IsStdPackage(pkgpath) && len(gd.Specs) != 0 {
-			pos = gd.Specs[0].Pos()
+		// Have existing grouped import ( ... ) decl.
+		if IsStdPackage(pkgpath) && len(gd.Specs) > 0 {
+			// Add spec for a std package before
+			// first existing spec, followed by
+			// a blank line if the next one is non-std.
+			first := gd.Specs[0].(*ast.ImportSpec)
+			pos = first.Pos()
+			if !IsStdPackage(first.Path.Value) {
+				newText += "\n"
+			}
 			newText += "\n\t"
 		} else {
+			// Add spec at end of group.
+			pos = gd.Rparen
 			newText = "\t" + newText + "\n"
 		}
 	} else {
+		// No import decl, or non-grouped import.
+		// Add a new import decl before first decl.
+		// (gofmt will merge multiple import decls.)
 		pos = before.Pos()
 		newText = "import " + newText + "\n\n"
 	}
