gopls/internal/server: Organize Imports of generated files

This CL causes CodeAction to offer the Organize Imports operation
even in generated files. Unlike most code actions with fixes,
which are a nuisance in generated files since the fix should be
applied to the generator logic not its output, Organize Imports
is invaluable when making experimental temporary edits in
generated files, such as adding logging statements.
Also, it is silent on files that are well formed,
which all unedited generated files must be.

+ test

Updates golang/go#49555
Fixes golang/go#73959

Change-Id: Ia72f5b40402175ecd80dc62e7c34e8b3cf51d011
Reviewed-on: https://go-review.googlesource.com/c/tools/+/678835
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: adonovan

gopls/internal/server/code_action.go

@@ -180,10 +180,16 @@ func (s *server) CodeAction(ctx context.Context, params *protocol.CodeActionPara
 		}
 		actions = append(actions, moreActions...)
 
-		// Don't suggest fixes for generated files, since they are generally
+		// Don't suggest most fixes for generated files, since they are generally
 		// not useful and some editors may apply them automatically on save.
 		// (Unfortunately there's no reliable way to distinguish fixes from
 		// queries, so we must list all kinds of queries here.)
+		//
+		// We make an exception for OrganizeImports, because
+		// (a) it is needed when making temporary experimental
+		//     changes (e.g. adding logging) in generated files, and
+		// (b) it doesn't report diagnostics on well-formed code, and
+		//     unedited generated files must be well formed.
 		if golang.IsGenerated(ctx, snapshot, uri) {
 			actions = slices.DeleteFunc(actions, func(a protocol.CodeAction) bool {
 				switch a.Kind {
@@ -194,6 +200,8 @@ func (s *server) CodeAction(ctx context.Context, params *protocol.CodeActionPara
 					settings.GoplsDocFeatures,
 					settings.GoToggleCompilerOptDetails:
 					return false // read-only query
+				case settings.OrganizeImports:
+					return false // fix allowed in generated files (see #73959)
 				}
 				return true // potential write operation
 			})

gopls/internal/test/marker/testdata/codeaction/imports-generated.txt

@@ -0,0 +1,27 @@
+This test verifies that the 'source.organizeImports' code action
+is offered in generated files (see #73959).
+
+-- go.mod --
+module example.com
+go 1.21
+
+-- a.go --
+// Code generated by me. DO NOT EDIT.
+
+package a //@codeaction("a", "source.organizeImports", result=out)
+
+func _() {
+	fmt.Println("hello") //@diag("fmt", re"undefined")
+}
+
+-- @out/a.go --
+// Code generated by me. DO NOT EDIT.
+
+package a //@codeaction("a", "source.organizeImports", result=out)
+
+import "fmt"
+
+func _() {
+	fmt.Println("hello") //@diag("fmt", re"undefined")
+}
+

gopls/internal/test/marker/testdata/format/generated.txt

@@ -13,7 +13,7 @@ go 1.21
 -- a/a.go --
 // Code generated by me. DO NOT EDIT.
 
-package a; func main() { fmt.Println("hello") }
+package a; import "fmt"; func main() { fmt.Println("hello") }
 
 //@format(out)
 
@@ -22,6 +22,8 @@ package a; func main() { fmt.Println("hello") }
 
 package a
 
+import "fmt"
+
 func main() { fmt.Println("hello") }
 
 //@format(out)