Improve performance of --list and --summary flags

Closes #332

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- Improve performance of `--list` and `--summary` by skipping running shell
+  variables for these flags
+  ([#332](https://github.com/go-task/task/issues/332)).
 - Fixed a bug where an environment in a Taskfile was not always overridable
   by the system environment
   ([#425](https://github.com/go-task/task/issues/425)).

help.go

@@ -30,7 +30,7 @@ func (e *Executor) tasksWithDesc() (tasks []*taskfile.Task) {
 	tasks = make([]*taskfile.Task, 0, len(e.Taskfile.Tasks))
 	for _, task := range e.Taskfile.Tasks {
 		if task.Desc != "" {
-			compiledTask, err := e.CompiledTask(taskfile.Call{Task: task.Task})
+			compiledTask, err := e.FastCompiledTask(taskfile.Call{Task: task.Task})
 			if err == nil {
 				task = compiledTask
 			}

internal/compiler/compiler.go

@@ -8,6 +8,7 @@ import (
 // E.g. variable merger, template processing, etc.
 type Compiler interface {
 	GetVariables(t *taskfile.Task, call taskfile.Call) (*taskfile.Vars, error)
+	FastGetVariables(t *taskfile.Task, call taskfile.Call) (*taskfile.Vars, error)
 	HandleDynamicVar(v taskfile.Var, dir string) (string, error)
 	ResetCache()
 }

internal/compiler/v2/compiler_v2.go

@@ -30,6 +30,11 @@ type CompilerV2 struct {
 	muDynamicCache sync.Mutex
 }
 
+// FastGetVariables is a no-op on v2
+func (c *CompilerV2) FastGetVariables(t *taskfile.Task, call taskfile.Call) (*taskfile.Vars, error) {
+	return c.GetVariables(t, call)
+}
+
 // GetVariables returns fully resolved variables following the priority order:
 // 1. Task variables
 // 2. Call variables

internal/compiler/v3/compiler_v3.go

@@ -30,6 +30,14 @@ type CompilerV3 struct {
 }
 
 func (c *CompilerV3) GetVariables(t *taskfile.Task, call taskfile.Call) (*taskfile.Vars, error) {
+	return c.getVariables(t, call, true)
+}
+
+func (c *CompilerV3) FastGetVariables(t *taskfile.Task, call taskfile.Call) (*taskfile.Vars, error) {
+	return c.getVariables(t, call, false)
+}
+
+func (c *CompilerV3) getVariables(t *taskfile.Task, call taskfile.Call, evaluateShVars bool) (*taskfile.Vars, error) {
 	result := compiler.GetEnviron()
 	result.Set("TASK", taskfile.Var{Static: t.Task})
 
@@ -37,6 +45,11 @@ func (c *CompilerV3) GetVariables(t *taskfile.Task, call taskfile.Call) (*taskfi
 		return func(k string, v taskfile.Var) error {
 			tr := templater.Templater{Vars: result, RemoveNoValue: true}
 
+			if !evaluateShVars {
+				result.Set(k, taskfile.Var{Static: tr.Replace(v.Static)})
+				return nil
+			}
+
 			v = taskfile.Var{
 				Static: tr.Replace(v.Static),
 				Sh:     tr.Replace(v.Sh),

task.go

@@ -71,7 +71,7 @@ func (e *Executor) Run(ctx context.Context, calls ...taskfile.Call) error {
 
 	if e.Summary {
 		for i, c := range calls {
-			compiledTask, err := e.CompiledTask(c)
+			compiledTask, err := e.FastCompiledTask(c)
 			if err != nil {
 				return nil
 			}

variables.go

@@ -13,12 +13,27 @@ import (
 // CompiledTask returns a copy of a task, but replacing variables in almost all
 // properties using the Go template package.
 func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
+	return e.compiledTask(call, true)
+}
+
+// FastCompiledTask is like CompiledTask, but it skippes dynamic variables.
+func (e *Executor) FastCompiledTask(call taskfile.Call) (*taskfile.Task, error) {
+	return e.compiledTask(call, false)
+}
+
+func (e *Executor) compiledTask(call taskfile.Call, evaluateShVars bool) (*taskfile.Task, error) {
 	origTask, ok := e.Taskfile.Tasks[call.Task]
 	if !ok {
 		return nil, &taskNotFoundError{call.Task}
 	}
 
-	vars, err := e.Compiler.GetVariables(origTask, call)
+	var vars *taskfile.Vars
+	var err error
+	if evaluateShVars {
+		vars, err = e.Compiler.GetVariables(origTask, call)
+	} else {
+		vars, err = e.Compiler.FastGetVariables(origTask, call)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -59,6 +74,7 @@ func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
 	new.Env = &taskfile.Vars{}
 	new.Env.Merge(r.ReplaceVars(e.Taskfile.Env))
 	new.Env.Merge(r.ReplaceVars(origTask.Env))
+	if evaluateShVars {
 		err = new.Env.Range(func(k string, v taskfile.Var) error {
 			static, err := e.Compiler.HandleDynamicVar(v, new.Dir)
 			if err != nil {
@@ -70,6 +86,7 @@ func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
 		if err != nil {
 			return nil, err
 		}
+	}
 
 	if len(origTask.Cmds) > 0 {
 		new.Cmds = make([]*taskfile.Cmd, len(origTask.Cmds))