Added new flag to generate a custom error for stringNameToValueMethod

.gitignore

@@ -28,4 +28,4 @@ coverage.txt
 .idea
 .vscode
 
-enumer
+./enumer

README.md

@@ -2,7 +2,7 @@
 
 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)
-maintained by [Álvaro López Espinosa](https://github.com/alvaroloes/enumer). 
+maintained by [Álvaro López Espinosa](https://github.com/alvaroloes/enumer).
 This was again forked here as (https://github.com/dmarkham/enumer) picking up where Álvaro left off.
 
 
@@ -41,6 +41,8 @@ Flags:
         if true, alternative string values method will be generated. Default: false
   -yaml
         if true, yaml marshaling methods will be generated. Default: false
+  -customerror
+        if true, a custom error will be returned by the `<Type>String` function. Default: false
 ```
 
 

endtoend_test.go

@@ -4,6 +4,7 @@
 
 // go command is not available on android
 
+//go:build !android
 // +build !android
 
 package main
@@ -12,7 +13,6 @@ import (
 	"fmt"
 	"go/build"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -40,7 +40,7 @@ func init() {
 // binary panics if the String method for X is not correct, including for error cases.
 
 func TestEndToEnd(t *testing.T) {
-	dir, err := ioutil.TempDir("", "stringer")
+	dir, err := os.MkdirTemp("", "stringer")
 	if err != nil {
 		t.Fatal(err)
 	}

enumer.go

@@ -1,8 +1,11 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+)
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringNameToValueMethod = `// %[1]sString retrieves an enum value from the enum constants string name.
 // Throws an error if the param is not part of the enum.
@@ -14,11 +17,12 @@ func %[1]sString(s string) (%[1]s, error) {
 	if val, ok := _%[1]sNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
-	return 0, fmt.Errorf("%%s does not belong to %[1]s values", s)
+	return 0, %[2]s
 }
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringValuesMethod = `// %[1]sValues returns all values of the enum
 func %[1]sValues() []%[1]s {
@@ -27,6 +31,7 @@ func %[1]sValues() []%[1]s {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringsMethod = `// %[1]sStrings returns a slice of all String values of the enum
 func %[1]sStrings() []string {
@@ -37,6 +42,7 @@ func %[1]sStrings() []string {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringBelongsMethodLoop = `// IsA%[1]s returns "true" if the value is listed in the enum definition. "false" otherwise
 func (i %[1]s) IsA%[1]s() bool {
@@ -50,6 +56,7 @@ func (i %[1]s) IsA%[1]s() bool {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringBelongsMethodSet = `// IsA%[1]s returns "true" if the value is listed in the enum definition. "false" otherwise
 func (i %[1]s) IsA%[1]s() bool {
@@ -59,6 +66,7 @@ func (i %[1]s) IsA%[1]s() bool {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const altStringValuesMethod = `func (%[1]s) Values() []string {
 	return %[1]sStrings()
@@ -70,7 +78,7 @@ func (g *Generator) buildAltStringValuesMethod(typeName string) {
 	g.Printf(altStringValuesMethod, typeName)
 }
 
-func (g *Generator) buildBasicExtras(runs [][]Value, typeName string, runsThreshold int) {
+func (g *Generator) buildBasicExtras(runs [][]Value, typeName string, runsThreshold int, customError bool) {
 	// At this moment, either "g.declareIndexAndNameVars()" or "g.declareNameVars()" has been called
 
 	// Print the slice of values
@@ -89,7 +97,12 @@ func (g *Generator) buildBasicExtras(runs [][]Value, typeName string, runsThresh
 	g.printNamesSlice(runs, typeName, runsThreshold)
 
 	// Print the basic extra methods
-	g.Printf(stringNameToValueMethod, typeName)
+	stringNameToValueErr := fmt.Sprintf(`fmt.Errorf("%%s does not belong to %s values", s)`, typeName)
+	if customError {
+		stringNameToValueErr = `enumer.InvalidEnumValueError`
+	}
+	g.Printf(stringNameToValueMethod, typeName, stringNameToValueErr)
+
 	g.Printf(stringValuesMethod, typeName)
 	g.Printf(stringsMethod, typeName)
 	if len(runs) <= runsThreshold {
@@ -144,6 +157,7 @@ func (g *Generator) printNamesSlice(runs [][]Value, typeName string, runsThresho
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const jsonMethods = `
 // MarshalJSON implements the json.Marshaler interface for %[1]s
@@ -169,6 +183,7 @@ func (g *Generator) buildJSONMethods(runs [][]Value, typeName string, runsThresh
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const textMethods = `
 // MarshalText implements the encoding.TextMarshaler interface for %[1]s
@@ -189,6 +204,7 @@ func (g *Generator) buildTextMethods(runs [][]Value, typeName string, runsThresh
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const yamlMethods = `
 // MarshalYAML implements a YAML Marshaler for %[1]s

golden_test.go

@@ -10,7 +10,6 @@
 package main
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -68,6 +67,10 @@ var goldenWithPrefix = []Golden{
 	{"dayWithPrefix", dayIn},
 }
 
+var goldenWithCustomError = []Golden{
+	{"dayWithCustomError", dayIn},
+}
+
 var goldenTrimAndAddPrefix = []Golden{
 	{"dayTrimAndPrefix", trimPrefixIn},
 }
@@ -315,52 +318,55 @@ const (
 
 func TestGolden(t *testing.T) {
 	for _, test := range golden {
-		runGoldenTest(t, test, false, false, false, false, false, false, true, "", "")
+		runGoldenTest(t, test, false, false, false, false, false, false, true, false, "", "")
 	}
 	for _, test := range goldenJSON {
-		runGoldenTest(t, test, true, false, false, false, false, false, false, "", "")
+		runGoldenTest(t, test, true, false, false, false, false, false, false, false, "", "")
 	}
 	for _, test := range goldenText {
-		runGoldenTest(t, test, false, false, false, true, false, false, false, "", "")
+		runGoldenTest(t, test, false, false, false, true, false, false, false, false, "", "")
 	}
 	for _, test := range goldenYAML {
-		runGoldenTest(t, test, false, true, false, false, false, false, false, "", "")
+		runGoldenTest(t, test, false, true, false, false, false, false, false, false, "", "")
 	}
 	for _, test := range goldenSQL {
-		runGoldenTest(t, test, false, false, true, false, false, false, false, "", "")
+		runGoldenTest(t, test, false, false, true, false, false, false, false, false, "", "")
 	}
 	for _, test := range goldenJSONAndSQL {
-		runGoldenTest(t, test, true, false, true, false, false, false, false, "", "")
+		runGoldenTest(t, test, true, false, true, false, false, false, false, false, "", "")
 	}
 	for _, test := range goldenGQLGen {
-		runGoldenTest(t, test, false, false, false, false, false, true, false, "", "")
+		runGoldenTest(t, test, false, false, false, false, false, true, false, false, "", "")
 	}
 	for _, test := range goldenTrimPrefix {
-		runGoldenTest(t, test, false, false, false, false, false, false, false, "Day", "")
+		runGoldenTest(t, test, false, false, false, false, false, false, false, false, "Day", "")
 	}
 	for _, test := range goldenTrimPrefixMultiple {
-		runGoldenTest(t, test, false, false, false, false, false, false, false, "Day,Night", "")
+		runGoldenTest(t, test, false, false, false, false, false, false, false, false, "Day,Night", "")
 	}
 	for _, test := range goldenWithPrefix {
-		runGoldenTest(t, test, false, false, false, false, false, false, false, "", "Day")
+		runGoldenTest(t, test, false, false, false, false, false, false, false, false, "", "Day")
+	}
+	for _, test := range goldenWithCustomError {
+		runGoldenTest(t, test, false, false, false, false, false, false, false, true, "", "Day")
 	}
 	for _, test := range goldenTrimAndAddPrefix {
-		runGoldenTest(t, test, false, false, false, false, false, false, false, "Day", "Night")
+		runGoldenTest(t, test, false, false, false, false, false, false, false, false, "Day", "Night")
 	}
 	for _, test := range goldenLinecomment {
-		runGoldenTest(t, test, false, false, false, false, true, false, false, "", "")
+		runGoldenTest(t, test, false, false, false, false, true, false, false, false, "", "")
 	}
 }
 
 func runGoldenTest(t *testing.T, test Golden,
-	generateJSON, generateYAML, generateSQL, generateText, linecomment, generateGQLGen, generateValuesMethod bool,
+	generateJSON, generateYAML, generateSQL, generateText, linecomment, generateGQLGen, generateValuesMethod bool, generateCustomError bool,
 	trimPrefix string, prefix string) {
 
 	var g Generator
 	file := test.name + ".go"
 	input := "package test\n" + test.input
 
-	dir, err := ioutil.TempDir("", "stringer")
+	dir, err := os.MkdirTemp("", "stringer")
 	if err != nil {
 		t.Error(err)
 	}
@@ -372,7 +378,7 @@ func runGoldenTest(t *testing.T, test Golden,
 	}()
 
 	absFile := filepath.Join(dir, file)
-	err = ioutil.WriteFile(absFile, []byte(input), 0644)
+	err = os.WriteFile(absFile, []byte(input), 0644)
 	if err != nil {
 		t.Error(err)
 	}
@@ -382,12 +388,12 @@ func runGoldenTest(t *testing.T, test Golden,
 	if len(tokens) != 3 {
 		t.Fatalf("%s: need type declaration on first line", test.name)
 	}
-	g.generate(tokens[1], generateJSON, generateYAML, generateSQL, generateText, generateGQLGen, "noop", trimPrefix, prefix, linecomment, generateValuesMethod)
+	g.generate(tokens[1], generateJSON, generateYAML, generateSQL, generateText, generateGQLGen, "noop", trimPrefix, prefix, linecomment, generateCustomError, generateValuesMethod)
 	got := string(g.format())
 	if got != loadGolden(test.name) {
 		// Use this to help build a golden text when changes are needed
 		//goldenFile := fmt.Sprintf("./testdata/%v.golden", test.name)
-		//err = ioutil.WriteFile(goldenFile, []byte(got), 0644)
+		//err = os.WriteFile(goldenFile, []byte(got), 0644)
 		//if err != nil {
 		//	t.Error(err)
 		//}
@@ -396,12 +402,7 @@ func runGoldenTest(t *testing.T, test Golden,
 }
 
 func loadGolden(name string) string {
-	fh, err := os.Open("testdata/" + name + ".golden")
-	if err != nil {
-		return ""
-	}
-	defer fh.Close()
-	b, err := ioutil.ReadAll(fh)
+	b, err := os.ReadFile("testdata/" + name + ".golden")
 	if err != nil {
 		return ""
 	}

pkg/enumer/enumer.go

@@ -0,0 +1,5 @@
+package enumer
+
+import "errors"
+
+var InvalidEnumValueError = errors.New("invalid enum value")

stringer.go

@@ -18,7 +18,6 @@ import (
 	"go/importer"
 	"go/token"
 	"go/types"
-	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
@@ -56,6 +55,7 @@ var (
 	trimPrefix      = flag.String("trimprefix", "", "transform each item name by removing a prefix or comma separated list of prefixes. Default: \"\"")
 	addPrefix       = flag.String("addprefix", "", "transform each item name by adding a prefix. Default: \"\"")
 	linecomment     = flag.Bool("linecomment", false, "use line comment text as printed text when present")
+	customError     = flag.Bool("customerror", false, "if true, a custom error will be returned by the `<Type>String` function. Default: false")
 )
 
 var comments arrayFlags
@@ -131,11 +131,15 @@ func main() {
 		g.Printf("\t\"io\"\n")
 		g.Printf("\t\"strconv\"\n")
 	}
+	if *customError {
+		g.Printf("\n\t\"github.com/dmarkham/enumer/pkg/enumer\"\n")
+	}
+
 	g.Printf(")\n")
 
 	// Run generate for each type.
 	for _, typeName := range typs {
-		g.generate(typeName, *json, *yaml, *sql, *text, *gqlgen, *transformMethod, *trimPrefix, *addPrefix, *linecomment, *altValuesFunc)
+		g.generate(typeName, *json, *yaml, *sql, *text, *gqlgen, *transformMethod, *trimPrefix, *addPrefix, *linecomment, *customError, *altValuesFunc)
 	}
 
 	// Format the output.
@@ -149,21 +153,19 @@ func main() {
 	}
 
 	// Write to tmpfile first
-	tmpFile, err := ioutil.TempFile(dir, fmt.Sprintf("%s_enumer_", typs[0]))
+	tmpFile, err := os.CreateTemp(dir, fmt.Sprintf("%s_enumer_", typs[0]))
 	if err != nil {
 		log.Fatalf("creating temporary file for output: %s", err)
 	}
-	_, err = tmpFile.Write(src)
-	if err != nil {
+	if _, err = tmpFile.Write(src); err != nil {
 		tmpFile.Close()
 		os.Remove(tmpFile.Name())
 		log.Fatalf("writing output: %s", err)
 	}
 	tmpFile.Close()
 
 	// Rename tmpfile to output file
-	err = os.Rename(tmpFile.Name(), outputName)
-	if err != nil {
+	if err := os.Rename(tmpFile.Name(), outputName); err != nil {
 		log.Fatalf("moving tempfile to output file: %s", err)
 	}
 }
@@ -415,7 +417,7 @@ func (g *Generator) prefixValueNames(values []Value, prefix string) {
 // generate produces the String method for the named type.
 func (g *Generator) generate(typeName string,
 	includeJSON, includeYAML, includeSQL, includeText, includeGQLGen bool,
-	transformMethod string, trimPrefix string, addPrefix string, lineComment bool, includeValuesMethod bool) {
+	transformMethod string, trimPrefix string, addPrefix string, lineComment bool, customError bool, includeValuesMethod bool) {
 	values := make([]Value, 0, 100)
 	for _, file := range g.pkg.files {
 		file.lineComment = lineComment
@@ -468,7 +470,7 @@ func (g *Generator) generate(typeName string,
 
 	g.buildNoOpOrderChangeDetect(runs, typeName)
 
-	g.buildBasicExtras(runs, typeName, runsThreshold)
+	g.buildBasicExtras(runs, typeName, runsThreshold, customError)
 	if includeJSON {
 		g.buildJSONMethods(runs, typeName, runsThreshold)
 	}