add support of task's targets set directly in playbook

README.md

@@ -283,6 +283,7 @@ Each task consists of a list of commands that will be executed on the remote hos
 
 - `on_error`: specifies the command to execute on the local host (the one running the `spot` command) in case of an error. The command can use the `{SPOT_ERROR}` variable to access the last error message. Example: `on_error: "curl -s localhost:8080/error?msg={SPOT_ERROR}"`
 - `user`: specifies the SSH user to use when connecting to remote hosts. Overrides the user defined in the top section of playbook file for the specified task.
+- `targets` - list of target names, group, tags or host addresses to execute the task on. Command line `-t` flag can be used to override this field. 
 
 *Note: these fields supported in the full playbook type only*
 
@@ -406,7 +407,7 @@ Targets are used to define the remote hosts to execute the tasks on. Targets can
 
 All the target types can be combined, i.e. `hosts`, `groups`, `tags`, `hosts` and `names` all can be used together in the same target. To avoid possible duplicates, the final list of hosts is deduplicated by the host+ip+user. 
 
-example of targets in the playbook file:
+example of targets set in the playbook file:
 
 ```yaml
 targets:
@@ -419,6 +420,13 @@ targets:
     names: ["host1", "host2"]
   all-servers:
     groups: ["all"]
+
+tasks:
+  - name: task1
+    targets: ["dev", "host3.example.com:2222"]
+    commands:
+      - name: command1
+        script: echo "Hello World"
 ```
 
 *Note: All the target types available in the full playbook file only. The simplified playbook file only supports a single, anonymous target type combining `hosts` and `names` together.*
@@ -449,7 +457,9 @@ The target selection is done in the following order:
   - if no match found, Spot will try to match on host name in the inventory file.
   - if no match found, Spot will try to match on host address in the playbook file.
   - if no match found, Spot will use it as a host address.
-- if `--target` is not discovered, Spot will assume the `default` target.
+- if `--target` is not set, Spot will try check it `targets` list for the task. If set, it will use it following the same logic as above.
+- and finally, Spot will assume the `default` target.
+
 
 ### Inventory 
 

cmd/spot/main.go

@@ -186,7 +186,7 @@ func run(opts options) error {
 	}
 
 	if opts.TaskName != "" { // run single task
-		for _, targetName := range opts.Targets {
+		for _, targetName := range targetsForTask(opts, opts.TaskName, conf) {
 			if err := runTaskForTarget(ctx, r, opts.TaskName, targetName); err != nil {
 				return err
 			}
@@ -196,7 +196,7 @@ func run(opts options) error {
 
 	// run all tasks
 	for _, taskName := range conf.Tasks {
-		for _, targetName := range opts.Targets {
+		for _, targetName := range targetsForTask(opts, opts.TaskName, conf) {
 			if err := runTaskForTarget(ctx, r, taskName.Name, targetName); err != nil {
 				return err
 			}
@@ -217,6 +217,40 @@ func runTaskForTarget(ctx context.Context, r runner.Process, taskName, targetNam
 	return nil
 }
 
+// get list of targets for task. Usually ths is just list of all targets from command line,
+// however if task has targets defined AND cli has default target, then only those targets will be used.
+func targetsForTask(opts options, taskName string, conf *config.PlayBook) []string {
+	if len(opts.Targets) > 1 || (len(opts.Targets) == 1 && opts.Targets[0] != "default") {
+		// non-default target specified on command line
+		return opts.Targets
+	}
+
+	lookupTask := func(name string) (tsk config.Task) {
+		// get task by name
+		for _, t := range conf.Tasks {
+			if t.Name == taskName {
+				tsk = t
+				return tsk
+			}
+		}
+		return tsk
+	}
+
+	tsk := lookupTask(taskName)
+	if tsk.Name == "" {
+		// this should never happen, task name is validated on playbook level
+		return opts.Targets
+	}
+
+	if len(tsk.Targets) == 0 {
+		// no targets defined for task
+		return opts.Targets
+	}
+
+	log.Printf("[INFO] task %q has %d targets [%s] pre-defined", taskName, len(tsk.Targets), strings.Join(tsk.Targets, ", "))
+	return tsk.Targets
+}
+
 // makeSecretsProvider creates secrets provider based on options
 func makeSecretsProvider(sopts SecretsProvider) (config.SecretsProvider, error) {
 	switch sopts.Provider {

cmd/spot/main_test.go

@@ -467,6 +467,93 @@ func Test_formatErrorString(t *testing.T) {
 	}
 }
 
+func Test_targetsForTask(t *testing.T) {
+	tests := []struct {
+		name           string
+		opts           options
+		taskName       string
+		conf           *config.PlayBook
+		expectedResult []string
+	}{
+		{
+			name: "non-default targets specified on command line",
+			opts: options{
+				Targets: []string{"target1", "target2"},
+			},
+			taskName:       "task1",
+			conf:           &config.PlayBook{},
+			expectedResult: []string{"target1", "target2"},
+		},
+		{
+			name: "task with targets defined and default in command line",
+			opts: options{
+				Targets: []string{"default"},
+			},
+			taskName: "task1",
+			conf: &config.PlayBook{
+				Tasks: []config.Task{
+					{
+						Name:    "task1",
+						Targets: []string{"target3", "target4"},
+					},
+				},
+			},
+			expectedResult: []string{"target3", "target4"},
+		},
+		{
+			name: "task without targets defined",
+			opts: options{
+				Targets: []string{"default"},
+			},
+			taskName: "task2",
+			conf: &config.PlayBook{
+				Tasks: []config.Task{
+					{
+						Name:    "task1",
+						Targets: []string{"target3", "target4"},
+					},
+					{
+						Name: "task2",
+					},
+				},
+			},
+			expectedResult: []string{"default"},
+		},
+		{
+			name: "default target with no task targets",
+			opts: options{
+				Targets: []string{"default"},
+			},
+			taskName:       "task3",
+			conf:           &config.PlayBook{},
+			expectedResult: []string{"default"},
+		},
+		{
+			name: "non-existing task",
+			opts: options{
+				Targets: []string{"default"},
+			},
+			taskName: "task3",
+			conf: &config.PlayBook{
+				Tasks: []config.Task{
+					{
+						Name:    "task1",
+						Targets: []string{"target3", "target4"},
+					},
+				},
+			},
+			expectedResult: []string{"default"},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			result := targetsForTask(tc.opts, tc.taskName, tc.conf)
+			assert.Equal(t, tc.expectedResult, result)
+		})
+	}
+}
+
 func startTestContainer(t *testing.T) (hostAndPort string, teardown func()) {
 	t.Helper()
 	ctx := context.Background()

pkg/config/playbook.go

@@ -52,10 +52,11 @@ type SimplePlayBook struct {
 
 // Task defines multiple commands runs together
 type Task struct {
-	Name     string `yaml:"name" toml:"name"` // name of target, set by config caller
-	User     string `yaml:"user" toml:"user"`
-	Commands []Cmd  `yaml:"commands" toml:"commands"`
-	OnError  string `yaml:"on_error" toml:"on_error"`
+	Name     string   `yaml:"name" toml:"name"` // name of target, set by config caller
+	User     string   `yaml:"user" toml:"user"`
+	Commands []Cmd    `yaml:"commands" toml:"commands"`
+	OnError  string   `yaml:"on_error" toml:"on_error"`
+	Targets  []string `yaml:"targets" toml:"targets"` // optional list of targets to run task on, names or groups
 }
 
 // Target defines hosts to run commands on