feat: add env subst command [CPE-1773] (#910)

* feat: add env subst command

* chore: lint

Author: KyleTryon

cmd/env.go

@@ -0,0 +1,47 @@
+package cmd
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/a8m/envsubst"
+	"github.com/spf13/cobra"
+)
+
+func newEnvCmd() *cobra.Command {
+	var envCmd = &cobra.Command{
+		Use:   "env",
+		Short: "Manage environment variables",
+	}
+	var substCmd = &cobra.Command{
+		Use:   "subst",
+		Short: "Substitute environment variables in a string",
+		RunE:  substRunE,
+	}
+	envCmd.AddCommand(substCmd)
+	return envCmd
+}
+
+// Accepts a string as an argument, or reads from stdin if no argument is provided.
+func substRunE(cmd *cobra.Command, args []string) error {
+	var input string
+	if len(args) > 0 {
+		input = args[0]
+	} else {
+		// Read from stdin
+		b, err := io.ReadAll(cmd.InOrStdin())
+		if err != nil {
+			return err
+		}
+		input = string(b)
+	}
+	if input == "" {
+		return nil
+	}
+	output, err := envsubst.String(input)
+	if err != nil {
+		return err
+	}
+	_, err = fmt.Fprint(cmd.OutOrStdout(), output)
+	return err
+}

cmd/env_test.go

@@ -0,0 +1,97 @@
+package cmd
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestSubstRunE(t *testing.T) {
+	// Set environment variables for testing
+	err := os.Setenv("ENV_NAME", "world")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testCases := []struct {
+		name   string
+		input  string
+		output string
+	}{
+		{
+			name:   "substitute variables",
+			input:  "Hello $ENV_NAME!",
+			output: "Hello world!",
+		},
+		{
+			name:   "no variables to substitute",
+			input:  "Hello, world!",
+			output: "Hello, world!",
+		},
+		{
+			name:   "empty input",
+			input:  "",
+			output: "",
+		},
+		{
+			name:   "no variables JSON",
+			input:  `{"foo": "bar"}`,
+			output: `{"foo": "bar"}`,
+		},
+		{
+			name:   "substitute variables JSON",
+			input:  `{"foo": "$ENV_NAME"}`,
+			output: `{"foo": "world"}`,
+		},
+		{
+			name:   "no variables key=value",
+			input:  `foo=bar`,
+			output: `foo=bar`,
+		},
+	}
+
+	// Run tests for each test case as argument
+	for _, tc := range testCases {
+		t.Run("arg: "+tc.name, func(t *testing.T) {
+			// Set up test command
+			cmd := newEnvCmd()
+
+			// Capture output
+			outputBuf := bytes.Buffer{}
+			cmd.SetOut(&outputBuf)
+
+			// Run command
+			cmd.SetArgs([]string{"subst", tc.input})
+			err := cmd.Execute()
+
+			// Check output and error
+			assert.NilError(t, err)
+			assert.Equal(t, tc.output, outputBuf.String())
+		})
+	}
+	// Run tests for each test case as stdin
+	for _, tc := range testCases {
+		t.Run("stdin: "+tc.name, func(t *testing.T) {
+			// Set up test command
+			cmd := newEnvCmd()
+
+			// Set up input
+			inputBuf := bytes.NewBufferString(tc.input)
+			cmd.SetIn(inputBuf)
+
+			// Capture output
+			outputBuf := bytes.Buffer{}
+			cmd.SetOut(&outputBuf)
+
+			// Run command
+			cmd.SetArgs([]string{"subst"})
+			err = cmd.Execute()
+
+			// Check output and error
+			assert.NilError(t, err)
+			assert.Equal(t, tc.output, outputBuf.String())
+		})
+	}
+}

cmd/root.go

@@ -174,6 +174,7 @@ func MakeCommands() *cobra.Command {
 	rootCmd.AddCommand(newSwitchCommand(rootOptions))
 	rootCmd.AddCommand(newAdminCommand(rootOptions))
 	rootCmd.AddCommand(newCompletionCommand())
+	rootCmd.AddCommand(newEnvCmd())
 
 	flags := rootCmd.PersistentFlags()
 

cmd/root_test.go

@@ -16,7 +16,7 @@ var _ = Describe("Root", func() {
 	Describe("subcommands", func() {
 		It("can create commands", func() {
 			commands := cmd.MakeCommands()
-			Expect(len(commands.Commands())).To(Equal(23))
+			Expect(len(commands.Commands())).To(Equal(24))
 		})
 	})
 

go.mod

@@ -41,6 +41,7 @@ require (
 
 require (
 	github.com/OneOfOne/xxhash v1.2.8 // indirect
+	github.com/a8m/envsubst v1.4.2 // indirect
 	github.com/agnivade/levenshtein v1.1.1 // indirect
 	github.com/atotto/clipboard v0.1.4 // indirect
 	github.com/charmbracelet/bubbles v0.11.0 // indirect

go.sum

@@ -43,6 +43,8 @@ github.com/Netflix/go-expect v0.0.0-20180615182759-c93bf25de8e8 h1:xzYJEypr/85nB
 github.com/Netflix/go-expect v0.0.0-20180615182759-c93bf25de8e8/go.mod h1:oX5x61PbNXchhh0oikYAH+4Pcfw5LKv21+Jnpr6r6Pc=
 github.com/OneOfOne/xxhash v1.2.8 h1:31czK/TI9sNkxIKfaUfGlU47BAxQ0ztGgd9vPyqimf8=
 github.com/OneOfOne/xxhash v1.2.8/go.mod h1:eZbhyaAYD41SGSSsnmcpxVoRiQ/MPUTjUdIIOT9Um7Q=
+github.com/a8m/envsubst v1.4.2 h1:4yWIHXOLEJHQEFd4UjrWDrYeYlV7ncFWJOCBRLOZHQg=
+github.com/a8m/envsubst v1.4.2/go.mod h1:MVUTQNGQ3tsjOOtKCNd+fl8RzhsXcDvvAEzkhGtlsbY=
 github.com/agnivade/levenshtein v1.1.1 h1:QY8M92nrzkmr798gCo3kmMyqXFzdQVpxLlGPRBij0P8=
 github.com/agnivade/levenshtein v1.1.1/go.mod h1:veldBMzWxcCG2ZvUTKD2kJNRdCk5hVbJomOvKkmgYbo=
 github.com/alcortesm/tgz v0.0.0-20161220082320-9c5fe88206d7 h1:uSoVVbwJiQipAclBbw+8quDsfcvFjOpI5iCf4p/cqCs=