feat: add Print method to entities

Method takes an io.Writer and writes the entity's unformatted code to
it. These methods are also used when generating the package source code
to reduce the amount of string builders.

entities.go

@@ -26,25 +26,32 @@ func (p *Package) Source() (string, error) {
 	return string(formatted), nil
 }
 
-// String returns the unformatted package signature source.
-func (p *Package) String() string {
-	var b strings.Builder
-
+// Print writes unformatted package code to writer.
+func (p *Package) Print(w io.Writer) {
 	if p.Doc != "" {
-		b.WriteString(mkComment(p.Doc))
+		fmt.Fprint(w, mkComment(p.Doc))
 	}
 
-	fmt.Fprintf(&b, "package %s", p.Name)
+	fmt.Fprintf(w, "package %s", p.Name)
 
 	for _, t := range p.Types {
-		fmt.Fprintf(&b, "\n\n%s", t)
+		fmt.Fprint(w, "\n\n")
+		t.Print(w)
 	}
 
 	for _, f := range p.Funcs {
-		fmt.Fprintf(&b, "\n\n%s", f)
+		fmt.Fprint(w, "\n\n")
+		f.Print(w)
 	}
 
-	b.WriteString("\n")
+	fmt.Fprint(w, "\n")
+}
+
+// String returns the unformatted package signature source.
+func (p *Package) String() string {
+	var b strings.Builder
+
+	p.Print(&b)
 
 	return b.String()
 }
@@ -71,27 +78,34 @@ func (f Func) IsExported() bool {
 	return isExportedIdent(f.Name)
 }
 
-// String returns the function signature code.
-func (f Func) String() string {
-	var b strings.Builder
-
+// Print writes unformatted function signature code to writer.
+func (f Func) Print(w io.Writer) {
 	if f.Doc != "" {
-		b.WriteString(mkComment(f.Doc))
+		fmt.Fprint(w, mkComment(f.Doc))
 	}
 
 	if f.funcKw {
-		b.WriteString("func ")
+		fmt.Fprint(w, "func ")
 	}
 
 	if f.Receiver != nil {
-		fmt.Fprintf(&b, "(%s) ", f.Receiver)
+		fmt.Fprint(w, "(")
+		f.Receiver.Print(w)
+		fmt.Fprint(w, ") ")
 	}
 
-	fmt.Fprintf(&b, "%s(%s) %s", f.Name, fieldsList(f.Params), resultsList(f.Results))
+	fmt.Fprintf(w, "%s(%s) %s", f.Name, fieldsList(f.Params), resultsList(f.Results))
 
 	if f.Comment != "" {
-		fmt.Fprintf(&b, " // %s", f.Comment)
+		fmt.Fprintf(w, " // %s", f.Comment)
 	}
+}
+
+// String returns the function signature code.
+func (f Func) String() string {
+	var b strings.Builder
+
+	f.Print(&b)
 
 	return b.String()
 }
@@ -122,34 +136,40 @@ func (td TypeDef) IsExported() bool {
 	return isExportedIdent(td.Name)
 }
 
-// String returns the type definition code.
-func (td TypeDef) String() string {
-	var b strings.Builder
-
+// Print writes unformatted type definition code to writer.
+func (td TypeDef) Print(w io.Writer) {
 	switch td.Type {
 	case "struct":
-		printStructType(&b, td)
+		printStructType(w, td)
 	case "interface":
-		printInterfaceType(&b, td)
+		printInterfaceType(w, td)
 	case "func":
-		printFuncType(&b, td)
+		printFuncType(w, td)
 	case "map":
-		printMapType(&b, td)
+		printMapType(w, td)
 	case "chan":
-		printChanType(&b, td)
+		printChanType(w, td)
 	case "array":
-		printArrayType(&b, td)
+		printArrayType(w, td)
 	default:
 		if td.Doc != "" {
-			b.WriteString(mkComment(td.Doc))
+			fmt.Fprint(w, mkComment(td.Doc))
 		}
 
-		fmt.Fprintf(&b, "type %s %s", td.Name, td.Type)
+		fmt.Fprintf(w, "type %s %s", td.Name, td.Type)
 
 		for _, m := range td.Methods {
-			fmt.Fprintf(&b, "\n\n%s", m)
+			fmt.Fprint(w, "\n\n")
+			m.Print(w)
 		}
 	}
+}
+
+// String returns the type definition code.
+func (td TypeDef) String() string {
+	var b strings.Builder
+
+	td.Print(&b)
 
 	return b.String()
 }
@@ -172,19 +192,24 @@ func (sf Field) IsExported() bool {
 	return isExportedIdent(sf.Names[0])
 }
 
-// String returns the unformatted struct field code fragment.
-func (sf Field) String() string {
-	var b strings.Builder
-
+// Print writes unformatted field code fragment to writer.
+func (sf Field) Print(w io.Writer) {
 	if sf.Doc != "" {
-		b.WriteString(mkComment(sf.Doc))
+		fmt.Fprint(w, mkComment(sf.Doc))
 	}
 
-	fmt.Fprintf(&b, "%s %s", strings.Join(sf.Names, ", "), sf.Type)
+	fmt.Fprintf(w, "%s %s", strings.Join(sf.Names, ", "), sf.Type)
 
 	if sf.Comment != "" {
-		fmt.Fprintf(&b, " // %s", sf.Comment)
+		fmt.Fprintf(w, " // %s", sf.Comment)
 	}
+}
+
+// String returns the unformatted field code fragment.
+func (sf Field) String() string {
+	var b strings.Builder
+
+	sf.Print(&b)
 
 	return b.String()
 }
@@ -200,7 +225,8 @@ func printStructType(w io.Writer, s TypeDef) {
 		fmt.Fprint(w, "\n")
 
 		for _, f := range s.Fields {
-			fmt.Fprintf(w, "    %s\n", f)
+			f.Print(w)
+			fmt.Fprint(w, "\n")
 		}
 	}
 
@@ -211,7 +237,8 @@ func printStructType(w io.Writer, s TypeDef) {
 	}
 
 	for _, fn := range s.Methods {
-		fmt.Fprintf(w, "\n\n%s", fn)
+		fmt.Fprint(w, "\n\n")
+		fn.Print(w)
 	}
 }