Add support for delegating CLI arguments with "--" and a special CLI_ARGS variable

Closes #327

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- Add support for delegating CLI arguments to commands with `--` and a
+  special `CLI_ARGS` variable
+  ([#327](https://github.com/go-task/task/issues/327)).
 - Add a `--concurrency` (alias `-C`) flag, to limit the number of tasks that
   run concurrently. This is useful for heavy workloads.
   ([#345](https://github.com/go-task/task/pull/345)).

args/args.go

@@ -9,7 +9,7 @@ import (
 // ParseV3 parses command line argument: tasks and global variables
 func ParseV3(args ...string) ([]taskfile.Call, *taskfile.Vars) {
 	var calls []taskfile.Call
-	var globals *taskfile.Vars
+	var globals = &taskfile.Vars{}
 
 	for _, arg := range args {
 		if !strings.Contains(arg, "=") {
@@ -17,9 +17,6 @@ func ParseV3(args ...string) ([]taskfile.Call, *taskfile.Vars) {
 			continue
 		}
 
-		if globals == nil {
-			globals = &taskfile.Vars{}
-		}
 		name, value := splitVar(arg)
 		globals.Set(name, taskfile.Var{Static: value})
 	}
@@ -34,7 +31,7 @@ func ParseV3(args ...string) ([]taskfile.Call, *taskfile.Vars) {
 // ParseV2 parses command line argument: tasks and vars of each task
 func ParseV2(args ...string) ([]taskfile.Call, *taskfile.Vars) {
 	var calls []taskfile.Call
-	var globals *taskfile.Vars
+	var globals = &taskfile.Vars{}
 
 	for _, arg := range args {
 		if !strings.Contains(arg, "=") {
@@ -43,9 +40,6 @@ func ParseV2(args ...string) ([]taskfile.Call, *taskfile.Vars) {
 		}
 
 		if len(calls) < 1 {
-			if globals == nil {
-				globals = &taskfile.Vars{}
-			}
 			name, value := splitVar(arg)
 			globals.Set(name, taskfile.Var{Static: value})
 		} else {

args/args_test.go

@@ -96,7 +96,9 @@ func TestArgsV3(t *testing.T) {
 		t.Run(fmt.Sprintf("TestArgs%d", i+1), func(t *testing.T) {
 			calls, globals := args.ParseV3(test.Args...)
 			assert.Equal(t, test.ExpectedCalls, calls)
-			assert.Equal(t, test.ExpectedGlobals, globals)
+			if test.ExpectedGlobals.Len() > 0 || globals.Len() > 0 {
+				assert.Equal(t, test.ExpectedGlobals, globals)
+			}
 		})
 	}
 }
@@ -198,7 +200,10 @@ func TestArgsV2(t *testing.T) {
 		t.Run(fmt.Sprintf("TestArgs%d", i+1), func(t *testing.T) {
 			calls, globals := args.ParseV2(test.Args...)
 			assert.Equal(t, test.ExpectedCalls, calls)
-			assert.Equal(t, test.ExpectedGlobals, globals)
+			if test.ExpectedGlobals.Len() > 0 || globals.Len() > 0 {
+				assert.Equal(t, test.ExpectedGlobals, globals)
+			}
+
 		})
 	}
 }

cmd/task/task.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strings"
 	"syscall"
 
 	"github.com/spf13/pflag"
@@ -157,14 +158,18 @@ func main() {
 	}
 
 	var (
-		calls   []taskfile.Call
-		globals *taskfile.Vars
+		calls                 []taskfile.Call
+		globals               *taskfile.Vars
+		tasksAndVars, cliArgs = getArgs()
 	)
+
 	if v >= 3.0 {
-		calls, globals = args.ParseV3(pflag.Args()...)
+		calls, globals = args.ParseV3(tasksAndVars...)
 	} else {
-		calls, globals = args.ParseV2(pflag.Args()...)
+		calls, globals = args.ParseV2(tasksAndVars...)
 	}
+
+	globals.Set("CLI_ARGS", taskfile.Var{Static: strings.Join(cliArgs, " ")})
 	e.Taskfile.Vars.Merge(globals)
 
 	ctx := context.Background()
@@ -185,6 +190,22 @@ func main() {
 	}
 }
 
+func getArgs() (tasksAndVars, cliArgs []string) {
+	var (
+		args          = pflag.Args()
+		doubleDashPos = pflag.CommandLine.ArgsLenAtDash()
+	)
+
+	if doubleDashPos != -1 {
+		tasksAndVars = args[:doubleDashPos]
+		cliArgs = args[doubleDashPos:]
+	} else {
+		tasksAndVars = args
+	}
+
+	return
+}
+
 func getSignalContext() context.Context {
 	ch := make(chan os.Signal, 1)
 	signal.Notify(ch, os.Interrupt, os.Kill, syscall.SIGTERM)

docs/usage.md

@@ -520,6 +520,27 @@ tasks:
 
 This works for all types of variables.
 
+## Forwarding CLI arguments to commands
+
+If `--` is given in the CLI, all following paramaters are added to a
+special `.CLI_ARGS` variable. This is useful to forward arguments to another
+command.
+
+The below example will run `yarn install`.
+
+```bash
+$ task yarn -- install
+```
+
+```yaml
+version: '3'
+
+tasks:
+  yarn:
+    cmds:
+      - yarn {{.CLI_ARGS}}
+```
+
 ## Go's template engine
 
 Task parse commands as [Go's template engine][gotemplate] before executing

internal/templater/templater.go

@@ -63,7 +63,7 @@ func (r *Templater) ReplaceSlice(strs []string) []string {
 }
 
 func (r *Templater) ReplaceVars(vars *taskfile.Vars) *taskfile.Vars {
-	if r.err != nil || vars == nil || len(vars.Keys) == 0 {
+	if r.err != nil || vars.Len() == 0 {
 		return nil
 	}
 

taskfile/var.go

@@ -75,7 +75,7 @@ func (vs *Vars) Range(yield func(key string, value Var) error) error {
 // ToCacheMap converts Vars to a map containing only the static
 // variables
 func (vs *Vars) ToCacheMap() (m map[string]interface{}) {
-	m = make(map[string]interface{}, len(vs.Keys))
+	m = make(map[string]interface{}, vs.Len())
 	vs.Range(func(k string, v Var) error {
 		if v.Sh != "" {
 			// Dynamic variable is not yet resolved; trigger
@@ -93,6 +93,14 @@ func (vs *Vars) ToCacheMap() (m map[string]interface{}) {
 	return
 }
 
+// Len returns the size of the map
+func (vs *Vars) Len() int {
+	if vs == nil {
+		return 0
+	}
+	return len(vs.Keys)
+}
+
 // Var represents either a static or dynamic variable.
 type Var struct {
 	Static string