Merge remote-tracking branch 'upstream/master'

README.md

@@ -1,11 +1,18 @@
-# Enumer
-Enumer generates Go code to get string names from enum values and viceversa.
-It is a fork of [Rob Pike’s Stringer tool](https://godoc.org/golang.org/x/tools/cmd/stringer) 
-but adding a *"string to enum value"* method to the generated code.
+#Enumer
+Enumer is a tool to generate Go code that adds useful methods to Go enums (constants with a specific type).
+It started as a fork of [Rob Pike’s Stringer tool](https://godoc.org/golang.org/x/tools/cmd/stringer).
 
-This is useful when you need to read enum values from the command line arguments, from a configuration file, 
+##Generated functions and methods
+When Enumer is applied to a type, it will generate three methods and one function:
+
+* A method `String()` that returns the string representation of the enum value. This makes the enum conform
+the `Stringer` interface, so whenever you print an enum value, you'll get the string name instead of a number.
+* A function `<Type>String(s string)` to get the enum value from its string representation. This is useful 
+when you need to read enum values from the command line arguments, from a configuration file, 
 from a REST API request... In short, from those places where using the real enum value (an integer) would 
-be almost meaningless or hard to trace or use by a human
+be almost meaningless or hard to trace or use by a human.
+* And two more methods, `MarshalJSON()` and `UnmarshalJSON()`, that makes the enum conform 
+the `json.Marshaler` and `json.Unmarshaler` interfaces. Very useful to use it in JSON APIs.
 
 For example, if we have an enum type called `Pill`,
 ```go
@@ -19,7 +26,7 @@ const (
 	Acetaminophen = Paracetamol
 )
 ```
-executing `enumer -type=Pill` will generate a new file with two methods:
+executing `enumer -type=Pill` will generate a new file with four methods:
 ```go
 func (i Pill) String() string {
     //...
@@ -28,6 +35,14 @@ func (i Pill) String() string {
 func PillString(s string) (Pill, error) {
     //...
 }
+
+func (i Pill) MarshalJSON() ([]byte, error) {
+	//...
+}
+
+func (i *Pill) UnmarshalJSON(data []byte) error {
+	//...
+}
 ```
 From now on, we can:
 ```go
@@ -43,17 +58,26 @@ if err != nil {
     return
 }
 // Now pill == Ibuprofen
+
+// Marshal/unmarshal to/from json strings, either directly or automatically when
+// the enum is a field of a struct
+pillJSON := Aspirin.MarshalJSON()
+// Now pillJSON == `"Aspirin"`
 ```
 
-The generated code is exactly the same as the Stringer tool plus the `<Type>String` method, so you can use
+The generated code is exactly the same as the Stringer tool plus the mentioned additions, so you can use
 **Enumer** where you are already using **Stringer** without any code change.
 
 ## How to use
-The usage of Enumer is the same as Stringer, no changes were introduced.
-For more information please refer to the [Stringer docs](https://godoc.org/golang.org/x/tools/cmd/stringer) 
+The usage of Enumer is the same as Stringer, so you can refer to the [Stringer docs](https://godoc.org/golang.org/x/tools/cmd/stringer)
+for more information.
+
+There is only one flag added: `noJSON`. If this flag is set to true (i.e. `enumer -type=Pill -noJSON`), 
+the JSON related methods won't be generated.
 
 ## Additional functions of this fork
 This fork additionally implements the Scanner and Valuer interface to use a enum seamlessly in a database model.
 
-## TODO
-- Add a flag to optionally generate implementation of Scanner und Valuer interface
+## Inspiring projects
+* [Stringer](https://godoc.org/golang.org/x/tools/cmd/stringer)
+* [jsonenums](https://github.com/campoy/jsonenums)

enumer.go

@@ -1,4 +1,5 @@
 package main
+
 import "fmt"
 
 // Arguments to format are:
@@ -19,7 +20,7 @@ func (g *Generator) buildValueToNameMap(runs [][]Value, typeName string, runsThr
 	var runID string
 	for i, values := range runs {
 		if thereAreRuns {
-			runID = "_" + fmt.Sprintf("%d",i)
+			runID = "_" + fmt.Sprintf("%d", i)
 			n = 0
 		} else {
 			runID = ""
@@ -33,3 +34,26 @@ func (g *Generator) buildValueToNameMap(runs [][]Value, typeName string, runsThr
 	g.Printf("}\n\n")
 	g.Printf(stringValueToNameMap, typeName)
 }
+
+// Arguments to format are:
+//	[1]: type name
+const jsonMethods = `
+func (i %[1]s) MarshalJSON() ([]byte, error) {
+	return json.Marshal(i.String())
+}
+
+func (i *%[1]s) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return fmt.Errorf("%[1]s should be a string, got %%s", data)
+	}
+
+	var err error
+	*i, err = %[1]sString(s)
+	return err
+}
+`
+
+func (g *Generator) buildJSONMethods(runs [][]Value, typeName string, runsThreshold int) {
+	g.Printf(jsonMethods, typeName)
+}

golden_test.go

@@ -30,6 +30,10 @@ var golden = []Golden{
 	{"prime", prime_in, prime_out},
 }
 
+var goldenJSON = []Golden {
+	{"prime", prime_json_in, prime_json_out},
+}
+
 // Each example starts with "type XXX [u]int", with a single space separating them.
 
 // Simple test: enumeration of type int starting at 0.
@@ -338,9 +342,100 @@ func PrimeString(s string) (Prime, error) {
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
 }
 `
+const prime_json_in = `type Prime int
+const (
+	p2 Prime = 2
+	p3 Prime = 3
+	p5 Prime = 5
+	p7 Prime = 7
+	p77 Prime = 7 // Duplicate; note that p77 doesn't appear below.
+	p11 Prime = 11
+	p13 Prime = 13
+	p17 Prime = 17
+	p19 Prime = 19
+	p23 Prime = 23
+	p29 Prime = 29
+	p37 Prime = 31
+	p41 Prime = 41
+	p43 Prime = 43
+)
+`
+
+const prime_json_out = `
+const _Prime_name = "p2p3p5p7p11p13p17p19p23p29p37p41p43"
+
+var _Prime_map = map[Prime]string{
+	2:  _Prime_name[0:2],
+	3:  _Prime_name[2:4],
+	5:  _Prime_name[4:6],
+	7:  _Prime_name[6:8],
+	11: _Prime_name[8:11],
+	13: _Prime_name[11:14],
+	17: _Prime_name[14:17],
+	19: _Prime_name[17:20],
+	23: _Prime_name[20:23],
+	29: _Prime_name[23:26],
+	31: _Prime_name[26:29],
+	41: _Prime_name[29:32],
+	43: _Prime_name[32:35],
+}
+
+func (i Prime) String() string {
+	if str, ok := _Prime_map[i]; ok {
+		return str
+	}
+	return fmt.Sprintf("Prime(%d)", i)
+}
+
+var _PrimeNameToValue_map = map[string]Prime{
+	_Prime_name[0:2]:   2,
+	_Prime_name[2:4]:   3,
+	_Prime_name[4:6]:   5,
+	_Prime_name[6:8]:   7,
+	_Prime_name[8:11]:  11,
+	_Prime_name[11:14]: 13,
+	_Prime_name[14:17]: 17,
+	_Prime_name[17:20]: 19,
+	_Prime_name[20:23]: 23,
+	_Prime_name[23:26]: 29,
+	_Prime_name[26:29]: 31,
+	_Prime_name[29:32]: 41,
+	_Prime_name[32:35]: 43,
+}
+
+func PrimeString(s string) (Prime, error) {
+	if val, ok := _PrimeNameToValue_map[s]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to Prime values", s)
+}
+
+func (i Prime) MarshalJSON() ([]byte, error) {
+	return json.Marshal(i.String())
+}
+
+func (i *Prime) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return fmt.Errorf("Prime should be a string, got %s", data)
+	}
+
+	var err error
+	*i, err = PrimeString(s)
+	return err
+}
+`
 
 func TestGolden(t *testing.T) {
 	for _, test := range golden {
+		runGoldenTest(t, test, false)
+	}
+	for _, test := range goldenJSON {
+		runGoldenTest(t, test, true)
+	}
+}
+
+func runGoldenTest(t *testing.T, test Golden, generateJSON bool) {
 	var g Generator
 	input := "package test\n" + test.input
 	file := test.name + ".go"
@@ -350,10 +445,9 @@ func TestGolden(t *testing.T) {
 	if len(tokens) != 3 {
 		t.Fatalf("%s: need type declaration on first line", test.name)
 	}
-		g.generate(tokens[1])
+	g.generate(tokens[1], generateJSON)
 	got := string(g.format())
 	if got != test.output {
 		t.Errorf("%s: got\n====\n%s====\nexpected\n====%s", test.name, got, test.output)
 	}
-	}
 }

stringer.go

@@ -82,6 +82,7 @@ import (
 
 var (
 	typeNames = flag.String("type", "", "comma-separated list of type names; must be set")
+	noJSON    = flag.Bool("noJSON", false, "if true, json marshaling methods will NOT be included. Default: false")
 	output    = flag.String("output", "", "output file name; default srcdir/<type>_string.go")
 )
 
@@ -98,7 +99,7 @@ func Usage() {
 
 func main() {
 	log.SetFlags(0)
-	log.SetPrefix("stringer: ")
+	log.SetPrefix("enumer: ")
 	flag.Usage = Usage
 	flag.Parse()
 	if len(*typeNames) == 0 {
@@ -135,11 +136,14 @@ func main() {
 	g.Printf("import (\n")
 	g.Printf("\t\"fmt\"\n")
 	g.Printf("\t\"database/sql/driver\"\n")
+	if !*noJSON {
+		g.Printf("\t\"encoding/json\"\n")
+	}
 	g.Printf(")\n")
 
 	// Run generate for each type.
 	for _, typeName := range types {
-		g.generate(typeName)
+		g.generate(typeName, !*noJSON)
 	}
 
 	// Format the output.
@@ -275,7 +279,7 @@ func (pkg *Package) check(fs *token.FileSet, astFiles []*ast.File) {
 }
 
 // generate produces the String method for the named type.
-func (g *Generator) generate(typeName string) {
+func (g *Generator) generate(typeName string, includeJSON bool) {
 	values := make([]Value, 0, 100)
 	for _, file := range g.pkg.files {
 		// Set the state for this run of the walker.
@@ -303,16 +307,21 @@ func (g *Generator) generate(typeName string) {
 	// being necessary for any realistic example other than bitmasks
 	// is very low. And bitmasks probably deserve their own analysis,
 	// to be done some other day.
+	const runsThreshold = 10
 	switch {
 	case len(runs) == 1:
 		g.buildOneRun(runs, typeName)
-	case len(runs) <= 10:
+	case len(runs) <= runsThreshold:
 		g.buildMultipleRuns(runs, typeName)
 	default:
 		g.buildMap(runs, typeName)
 	}
-	// ENUMER: This is the only addition over the original stringer code. Everything else is in enumer.go
-	g.buildValueToNameMap(runs, typeName, 10)
+
+	// ENUMER part
+	g.buildValueToNameMap(runs, typeName, runsThreshold)
+	if includeJSON {
+		g.buildJSONMethods(runs, typeName, runsThreshold)
+	}
 
 	// SQL
 	g.addValueAndScanMethod(typeName)