cli: Allow user to specify dest filename for nomad init (#6520)

* Allow user to specify dest filename for nomad init
* Create changelog entry for GH-6520

CHANGELOG.md

@@ -7,6 +7,7 @@ FEATURES:
 
 IMPROVEMENTS:
 
+* cli: Added option to change the name of the file created by the `nomad init` command [[GH-6520]](https://github.com/hashicorp/nomad/pull/6520)
 * scheduler: Removed penalty for allocation's previous node if the allocation did not fail. [[GH-6781](https://github.com/hashicorp/nomad/issues/6781)]
 * scheduler: Reduced logging verbosity during preemption [[GH-6849](https://github.com/hashicorp/nomad/issues/6849)]
 

command/job_init.go

@@ -23,11 +23,11 @@ type JobInitCommand struct {
 
 func (c *JobInitCommand) Help() string {
 	helpText := `
-Usage: nomad job init
-Alias: nomad init
+Usage: nomad job init <filename>
+Alias: nomad init <filename>
 
-  Creates an example job file that can be used as a starting
-  point to customize further.
+  Creates an example job file that can be used as a starting point to customize
+  further. If no filename is given, the default of "example.nomad" will be used.
 
 Init Options:
 
@@ -71,20 +71,27 @@ func (c *JobInitCommand) Run(args []string) int {
 	}
 
 	// Check for misuse
-	if len(flags.Args()) != 0 {
-		c.Ui.Error("This command takes no arguments")
+	// Check that we either got no filename or exactly one.
+	args = flags.Args()
+	if len(args) > 1 {
+		c.Ui.Error("This command takes either no arguments or one: <filename>")
 		c.Ui.Error(commandErrorText(c))
 		return 1
 	}
 
+	filename := DefaultInitName
+	if len(args) == 1 {
+		filename = args[0]
+	}
+
 	// Check if the file already exists
-	_, err := os.Stat(DefaultInitName)
+	_, err := os.Stat(filename)
 	if err != nil && !os.IsNotExist(err) {
-		c.Ui.Error(fmt.Sprintf("Failed to stat '%s': %v", DefaultInitName, err))
+		c.Ui.Error(fmt.Sprintf("Failed to stat '%s': %v", filename, err))
 		return 1
 	}
 	if !os.IsNotExist(err) {
-		c.Ui.Error(fmt.Sprintf("Job '%s' already exists", DefaultInitName))
+		c.Ui.Error(fmt.Sprintf("Job '%s' already exists", filename))
 		return 1
 	}
 
@@ -107,13 +114,13 @@ func (c *JobInitCommand) Run(args []string) int {
 	}
 
 	// Write out the example
-	err = ioutil.WriteFile(DefaultInitName, jobSpec, 0660)
+	err = ioutil.WriteFile(filename, jobSpec, 0660)
 	if err != nil {
-		c.Ui.Error(fmt.Sprintf("Failed to write '%s': %v", DefaultInitName, err))
+		c.Ui.Error(fmt.Sprintf("Failed to write '%s': %v", filename, err))
 		return 1
 	}
 
 	// Success
-	c.Ui.Output(fmt.Sprintf("Example job file written to %s", DefaultInitName))
+	c.Ui.Output(fmt.Sprintf("Example job file written to %s", filename))
 	return 0
 }

command/job_init_test.go

@@ -88,3 +88,58 @@ func TestInitCommand_defaultJob(t *testing.T) {
 		t.Error("default job contains tab character - please convert to spaces")
 	}
 }
+
+func TestInitCommand_customFilename(t *testing.T) {
+	t.Parallel()
+	ui := new(cli.MockUi)
+	cmd := &JobInitCommand{Meta: Meta{Ui: ui}}
+	filename := "custom.nomad"
+
+	// Ensure we change the cwd back
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.Chdir(origDir)
+
+	// Create a temp dir and change into it
+	dir, err := ioutil.TempDir("", "nomad")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer os.RemoveAll(dir)
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Works if the file doesn't exist
+	if code := cmd.Run([]string{filename}); code != 0 {
+		t.Fatalf("expect exit code 0, got: %d", code)
+	}
+	content, err := ioutil.ReadFile(filename)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defaultJob, _ := Asset("command/assets/example.nomad")
+	if string(content) != string(defaultJob) {
+		t.Fatalf("unexpected file content\n\n%s", string(content))
+	}
+
+	// Works with -short flag
+	os.Remove(filename)
+	if code := cmd.Run([]string{"-short", filename}); code != 0 {
+		require.Zero(t, code, "unexpected exit code: %d", code)
+	}
+	content, err = ioutil.ReadFile(filename)
+	require.NoError(t, err)
+	shortJob, _ := Asset("command/assets/example-short.nomad")
+	require.Equal(t, string(content), string(shortJob))
+
+	// Fails if the file exists
+	if code := cmd.Run([]string{filename}); code != 1 {
+		t.Fatalf("expect exit code 1, got: %d", code)
+	}
+	if out := ui.ErrorWriter.String(); !strings.Contains(out, "exists") {
+		t.Fatalf("expect file exists error, got: %s", out)
+	}
+}

website/source/docs/commands/job/init.html.md

@@ -14,15 +14,18 @@ The `job init` command creates an example [job specification][jobspec] in the
 current directory that demonstrates some common configurations for tasks, task
 groups, runtime constraints, and resource allocation.
 
-Please refer to the [jobspec] and [drivers] pages to learn how to customize the
-template.
-
 ## Usage
 
 ```plaintext
-nomad job init [options]
+nomad job init [options] [filename]
 ```
 
+You may optionally supply a filename for the example job to be written to. The
+default filename for the generated file is "example.nomad".
+
+Please refer to the [jobspec] and [drivers] pages to learn how to customize the
+template.
+
 ## Init Options
 
 - `-short`: If set, a minimal jobspec without comments is emitted.
@@ -38,4 +41,4 @@ Example job file written to example.nomad
 ```
 
 [jobspec]: /docs/job-specification/index.html "Nomad Job Specification"
-[drivers]: /docs/drivers/index.html
+[drivers]: /docs/drivers/index.html "Nomad Task Drivers documentation"