Allow commandline directives (#401)

Make it possible to add directives as commandline parameter.

Alternatively to `//msgp:tag json` directives can also be specified using the `-d` flag. Example: `msgp -d "tag json"`. Multiple flags can be added.

Directives in files take precedence over commandline.

Bonus: Print info on all directives.

Author: klauspost

_generated/compactfloats.go

@@ -1,14 +1,10 @@
 package _generated
 
-//go:generate msgp
-
-//msgp:compactfloats
+//go:generate msgp -d "msgp:compactfloats" -d "replace F64 with:float64" -v
 
 //msgp:ignore F64
 type F64 float64
 
-//msgp:replace F64 with:float64
-
 type Floats struct {
 	A     float64
 	B     float32

_generated/custom_tag.go

@@ -1,7 +1,6 @@
 package _generated
 
-//go:generate msgp
-//msgp:tag mytag
+//go:generate msgp -d "tag mytag"
 
 type CustomTag struct {
 	Foo string `mytag:"foo_custom_name"`

main.go

@@ -41,6 +41,7 @@ var (
 	tests      = flag.Bool("tests", true, "create tests and benchmarks")
 	unexported = flag.Bool("unexported", false, "also process unexported types")
 	verbose    = flag.Bool("v", false, "verbose diagnostics")
+	directives = stringArrFlags{}
 )
 
 func diagf(f string, args ...interface{}) {
@@ -59,12 +60,17 @@ func exitln(res string) {
 }
 
 func main() {
+	flag.Var(&directives, "d", "apply directive to all files. Multiple -d flags allowed. 'msgp:' can be omitted")
 	flag.Parse()
 
 	if *verbose {
 		printer.Logf = diagf
 		parse.Logf = diagf
 	}
+	for i, v := range directives {
+		// Trim prefix and whitespace, if any.
+		directives[i] = strings.TrimPrefix(strings.TrimSpace(v), "msgp:")
+	}
 
 	// GOFILE is set by go generate
 	if *file == "" {
@@ -102,7 +108,7 @@ func Run(gofile string, mode gen.Method, unexported bool) error {
 		return nil
 	}
 	diagf("Input: \"%s\"\n", gofile)
-	fs, err := parse.File(gofile, unexported)
+	fs, err := parse.File(gofile, unexported, directives)
 	if err != nil {
 		return err
 	}
@@ -130,3 +136,17 @@ func newFilename(old string, pkg string) string {
 	// new file name is old file name + _gen.go
 	return strings.TrimSuffix(old, ".go") + "_gen.go"
 }
+
+// stringArrFlags is a flag.Value that accepts multiple values
+type stringArrFlags []string
+
+// String is an implementation of the flag.Value interface
+func (i *stringArrFlags) String() string {
+	return fmt.Sprintf("%v", *i)
+}
+
+// Set is an implementation of the flag.Value interface
+func (i *stringArrFlags) Set(value string) error {
+	*i = append(*i, value)
+	return nil
+}

parse/directives.go

@@ -219,29 +219,34 @@ func tag(text []string, f *FileSet) error {
 		return nil
 	}
 	f.tagName = strings.TrimSpace(text[1])
+	infof("using field tag %q\n", f.tagName)
 	return nil
 }
 
 //msgp:pointer
 func pointer(text []string, f *FileSet) error {
+	infof("using pointer receiver\n")
 	f.pointerRcv = true
 	return nil
 }
 
 //msgp:compactfloats
 func compactfloats(text []string, f *FileSet) error {
+	infof("using compact floats\n")
 	f.CompactFloats = true
 	return nil
 }
 
 //msgp:clearomitted
 func clearomitted(text []string, f *FileSet) error {
+	infof("clearing omitted fields\n")
 	f.ClearOmitted = true
 	return nil
 }
 
 //msgp:newtime
 func newtime(text []string, f *FileSet) error {
+	infof("using new time encoding\n")
 	f.NewTime = true
 	return nil
 }
@@ -307,5 +312,6 @@ func newtimezone(text []string, f *FileSet) error {
 	default:
 		return fmt.Errorf("timezone directive should be either 'local' or 'utc'; found %q", text[1])
 	}
+	infof("using timezone %q\n", text[1])
 	return nil
 }

parse/getast.go

@@ -39,12 +39,13 @@ type FileSet struct {
 // directory will be parsed.
 // If unexport is false, only exported identifiers are included in the FileSet.
 // If the resulting FileSet would be empty, an error is returned.
-func File(name string, unexported bool) (*FileSet, error) {
+func File(name string, unexported bool, directives []string) (*FileSet, error) {
 	pushstate(name)
 	defer popstate()
 	fs := &FileSet{
 		Specs:      make(map[string]ast.Expr),
 		Identities: make(map[string]gen.Elem),
+		Directives: append([]string{}, directives...),
 	}
 
 	fset := token.NewFileSet()
@@ -81,7 +82,7 @@ func File(name string, unexported bool) (*FileSet, error) {
 			return nil, err
 		}
 		fs.Package = f.Name.Name
-		fs.Directives = yieldComments(f.Comments)
+		fs.Directives = append(fs.Directives, yieldComments(f.Comments)...)
 		if !unexported {
 			ast.FileExports(f)
 		}