feature: Add list-themes option (#50)

* go mod tidy

* Use short variable declarations

* Add listThemes flag

* Add func: printThems

* Tweak yml

* Organize variables

* Print sample code with syntax-hilight

* Add TestListThemesFlag

.github/workflows/go.yml

@@ -32,7 +32,6 @@ jobs:
     - name: Run GoReleaser
       uses: goreleaser/goreleaser-action@master
       with:
-        version: latest
         args: release --snapshot --skip-publish --rm-dist
     # GitHub Actions doesn't support colored output, so comment it out temporarily.
     # - name: Colored Output Test

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     name: goreleaser
     steps:
-    - name: Set up Go 1.13.x
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
         go-version: 1.13

go.mod

@@ -10,5 +10,4 @@ require (
 	github.com/mattn/go-isatty v0.0.10
 	github.com/spf13/cobra v0.0.5
 	github.com/stretchr/testify v1.3.0
-	golang.org/x/sys v0.0.0-20190726091711-fc99dfbffb4e // indirect
 )

go.sum

@@ -4,8 +4,6 @@ github.com/GeertJohan/go.rice v1.0.0/go.mod h1:eH6gbSOAUv07dQuZVnBmoDP8mgsM1rtix
 github.com/akavel/rsrc v0.8.0/go.mod h1:uLoCtb9J+EyAqh+26kdrTgmzRBFPGOolLWKpdxkKq+c=
 github.com/alecthomas/assert v0.0.0-20170929043011-405dbfeb8e38 h1:smF2tmSOzy2Mm+0dGI2AIUHY+w0BUc+4tn40djz7+6U=
 github.com/alecthomas/assert v0.0.0-20170929043011-405dbfeb8e38/go.mod h1:r7bzyVFMNntcxPZXK3/+KdruV1H5KSlyVY0gc+NgInI=
-github.com/alecthomas/chroma v0.6.6 h1:AwWMP1sWgMNgEiptNtV/T5GWOLtZFDdrc2ZfWx1ogmg=
-github.com/alecthomas/chroma v0.6.6/go.mod h1:zVlgtbRS7BJDrDY9SB238RmpoCBCYFlLmcfZ3durxTk=
 github.com/alecthomas/chroma v0.6.7 h1:1hKci+AyKOxJrugR9veaocu9DQGR2/GecI72BpaO0Rg=
 github.com/alecthomas/chroma v0.6.7/go.mod h1:zVlgtbRS7BJDrDY9SB238RmpoCBCYFlLmcfZ3durxTk=
 github.com/alecthomas/colour v0.0.0-20160524082231-60882d9e2721 h1:JHZL0hZKJ1VENNfmXvHbgYlbUOvpzYzvy2aZU5gXVeo=
@@ -43,8 +41,6 @@ github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJS
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mattn/go-colorable v0.0.9 h1:UVL0vNpWh04HeJXV0KLcaT7r06gOH2l4OW6ddYRUIY4=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
-github.com/mattn/go-colorable v0.1.2 h1:/bC9yWikZXAL9uJdulbSfyVNIR3n3trXl+v8+1sx8mU=
-github.com/mattn/go-colorable v0.1.2/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-colorable v0.1.4 h1:snbPLB8fVfU9iwbbo30TPtbLRzwWu6aJS6Xh4eaaviA=
 github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-isatty v0.0.4/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
@@ -83,8 +79,6 @@ golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnf
 golang.org/x/sys v0.0.0-20181128092732-4ed8d59d0b35/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190726091711-fc99dfbffb4e h1:D5TXcfTk7xF7hvieo4QErS3qqCB4teTffacDWr7CI+0=
-golang.org/x/sys v0.0.0-20190726091711-fc99dfbffb4e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be h1:QAcqgptGM8IQBC9K/RC4o+O9YmqEm0diQn9QmZw/0mU=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

main.go

@@ -15,7 +15,10 @@ import (
 )
 
 var (
-	version     = "dev"
+	isTerminalFunc = isatty.IsTerminal
+	version        = "dev"
+
+	listThemes  bool
 	showVersion bool
 	theme       string
 )
@@ -30,12 +33,10 @@ $ nyan -t solarized-dark FILE1`,
 	RunE: cmdMain,
 }
 
-var isTerminalFunc = isatty.IsTerminal
-
 func init() {
 	rootCmd.PersistentFlags().BoolVarP(&showVersion, "version", "v", false, `show version`)
-	rootCmd.PersistentFlags().StringVarP(&theme, "theme", "t", "monokai", fmt.Sprintf(`color theme
-available themes: %s`, styles.Names()))
+	rootCmd.PersistentFlags().StringVarP(&theme, "theme", "t", "monokai", fmt.Sprintf("color theme\navailable themes: %s", styles.Names()))
+	rootCmd.PersistentFlags().BoolVarP(&listThemes, "list-themes", "T", false, `list available themes`)
 }
 
 func main() {
@@ -51,23 +52,25 @@ func cmdMain(cmd *cobra.Command, args []string) (err error) {
 	if showVersion {
 		cmd.Println("version", version)
 		return
+	} else if listThemes {
+		printThemes(cmd)
+		return
 	}
 
 	var data []byte
-	var lexer chroma.Lexer
 
 	if len(args) < 1 || args[0] == "-" {
 		if data, err = ioutil.ReadAll(cmd.InOrStdin()); err != nil {
 			return
 		}
-		lexer = lexers.Analyse(string(data))
+		lexer := lexers.Analyse(string(data))
 		printData(&data, cmd, lexer)
 	} else {
 		for _, filename := range args {
 			if data, err = ioutil.ReadFile(filename); err != nil {
 				cmd.Println(err)
 			}
-			lexer = lexers.Match(filename)
+			lexer := lexers.Match(filename)
 			printData(&data, cmd, lexer)
 		}
 	}
@@ -87,3 +90,22 @@ func printData(data *[]byte, cmd *cobra.Command, lexer chroma.Lexer) {
 		cmd.Print(string(*data))
 	}
 }
+
+const sampleCode = `package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello nyan cat command 😺")
+}
+`
+
+func printThemes(cmd *cobra.Command) {
+	for _, theme = range styles.Names() {
+		cmd.Println("Theme: ", theme)
+		code := []byte(sampleCode)
+		lexer := lexers.Get("go")
+		printData(&code, cmd, lexer)
+		cmd.Println()
+	}
+}

main_test.go

@@ -121,6 +121,18 @@ func TestVersionFlag(t *testing.T) {
 	assert.Contains(t, o.String(), "version ")
 }
 
+func TestListThemesFlag(t *testing.T) {
+	o := bytes.NewBufferString("")
+	rootCmd.SetArgs([]string{"--list-themes"})
+	rootCmd.SetOut(o)
+	err := rootCmd.Execute()
+	resetFlags()
+
+	assert.Nil(t, err)
+	assert.NotNil(t, o.String())
+	assert.Contains(t, o.String(), "Theme: ")
+}
+
 func TestUnknownFile(t *testing.T) {
 	o := bytes.NewBufferString("")
 	rootCmd.SetArgs([]string{"testdata/dummyfile"})
@@ -136,7 +148,7 @@ func TestFromStdIn(t *testing.T) {
 	i := bytes.NewBufferString("package main")
 	o := bytes.NewBufferString("")
 	isTerminalFunc = func(fd uintptr) bool { return true }
-	rootCmd.SetArgs([]string{})
+	rootCmd.SetArgs([]string{"-t", "monokai"})
 	rootCmd.SetIn(i)
 	rootCmd.SetOut(o)
 	err := rootCmd.Execute()
@@ -213,6 +225,7 @@ func TestShell(t *testing.T) {
 
 func resetFlags() {
 	showVersion = false
+	listThemes = false
 	rootCmd.Flags().Set("help", "false")
 }