.

go/xcommon/tracing/cmd/gotrace/gotrace.go

@@ -494,6 +494,7 @@ func (s StrSet) Itemv() []string {
 	return itemv
 }
 
+/*
 // findPackageNoZTrace is (*build.Context).Import but filters-out ztrace* files from found package
 //
 // we don't load what should be generated by us for 2 reasons:
@@ -528,6 +529,7 @@ func findPackageNoZTrace(ctxt *build.Context, importPath, fromDir string, mode b
 
 	return bp, err
 }
+*/
 
 // tracegen generates code according to tracing directives in a package @ pkgpath
 //
@@ -536,12 +538,36 @@ func findPackageNoZTrace(ctxt *build.Context, importPath, fromDir string, mode b
 func tracegen(pkgpath string, ctxt *build.Context, cwd string) error {
 	// TODO test-only with .TestGoFiles  .XTestGoFiles
 
+	// filter-out ztrace* files when disovering packages
+	//
+	// we don't load what should be generated by us for 2 reasons:
+	// - code generated could be wrong with older version of the
+	//   tool - it should not prevent from regenerating.
+	// - generated code imports packages which might be not there
+	//   yet in gopath (lab.nexedi.com/kirr/go123/tracing)
+	ctxtReadDir := ctxt.ReadDir
+	if ctxtReadDir == nil {
+		ctxtReadDir = ioutil.ReadDir
+	}
+	ctxtNoZTrace := *ctxt
+	ctxtNoZTrace.ReadDir = func(dir string) ([]os.FileInfo, error) {
+		fv, err := ctxtReadDir(dir)
+		okv := fv[:0]
+		for _, f := range fv {
+			if !strings.HasPrefix(f.Name(), "ztrace") {
+				okv = append(okv, f)
+			}
+		}
+		return okv, err
+	}
+
+	// XXX text
 	conf := loader.Config{
 		ParserMode: parser.ParseComments,
 		TypeCheckFuncBodies: func(path string) bool { return false },
-		Build: ctxt,
+		Build: &ctxtNoZTrace,
 		Cwd: cwd,
-		FindPackage: findPackageNoZTrace,
+//		FindPackage: findPackageNoZTrace,
 	}
 	conf.Import(pkgpath)
 
@@ -570,6 +596,14 @@ func tracegen(pkgpath string, ctxt *build.Context, cwd string) error {
 		return err // XXX err ctx
 	}
 
+	// write ztrace.go with code generated for trace events and imports
+	ztrace_go := filepath.Join(pkgdir, "ztrace.go")
+	if len(tpkg.Eventv) == 0 && len(tpkg.Importv) == 0 {
+		err = removeFile(ztrace_go)
+		if err != nil {
+			return err
+		}
+	} else {
 		// prologue
 		prologue := &Buffer{}
 		prologue.WriteString(magic)
@@ -637,17 +671,18 @@ func tracegen(pkgpath string, ctxt *build.Context, cwd string) error {
 
 		// write output to ztrace.go
 		fulltext := append(prologue.Bytes(), text.Bytes()...)
-	err = writeFile(filepath.Join(pkgdir, "ztrace.go"), fulltext)
+		err = writeFile(ztrace_go, fulltext)
 		if err != nil {
 			return err
 		}
+	}
 
 	// write empty ztrace.s so go:linkname works, if there are trace imports
 	ztrace_s := filepath.Join(pkgdir, "ztrace.s")
 	if len(tpkg.Importv) == 0 {
 		err = removeFile(ztrace_s)
 	} else {
-		text.Reset()
+		text := &Buffer{}
 		text.WriteString(magic)
 		text.emit("// empty .s so `go build` does not use -complete for go:linkname to work")
 

go/xcommon/tracing/cmd/gotrace/gotrace_test.go

@@ -136,7 +136,8 @@ func TestGoTraceGen(t *testing.T) {
 	}
 
 	// XXX autodetect (go list ?)
-	testv := []string{"a/pkg1", "b/pkg2", "c/pkg3"}
+	//testv := []string{"a/pkg1", "b/pkg2", "c/pkg3", "d/pkg4"}
+	testv := []string{"a/pkg1"}
 
 	for _, tpkg := range testv {
 		err = tracegen(tpkg, tBuildCtx, "" /* = local imorts disabled */)

go/xcommon/tracing/cmd/gotrace/testdata/src/a/pkg1/ztrace.go

 // Code generated by lab.nexedi.com/kirr/go123/tracing/cmd/gotrace; DO NOT EDIT.
 
-package pkg1
-
-import (
-	"non-existent"
-)
-
 Bad bad bad - I'm invalid go file.

go/xcommon/tracing/cmd/gotrace/testdata/src/d/pkg4/pkg4.go

+package pkg4
+
+// this package does not use tracepoints at all