Expose timestamp and checksum to status

docs/usage.md

@@ -340,6 +340,16 @@ tasks:
       - test -f directory/file2.txt
 ```
 
+Normally, you would use either `status` or `sources` in combination with
+`generates` - but for tasks that generate remote artifacts (docker images,
+deploys, CD releases) the checksum source and timestamps require either
+access to the artifact or for an out-of-band refresh of the `.checksum`
+fingerprint file.
+
+Two special variables `{{.CHECKSUM}}` and `{{.TIMESTAMP}}` are available
+for interpolation within `status` commands, depending on the method assigned
+to fingerprint the sources.  Only `source` globs are fingerprinted.
+
 You can use `--force` or `-f` if you want to force a task to run even when
 up-to-date.
 

internal/status/checksum.go

@@ -46,6 +46,10 @@ func (c *Checksum) IsUpToDate() (bool, error) {
 	return oldMd5 == newMd5, nil
 }
 
+func (t *Checksum) Kind() string {
+	return "checksum"
+}
+
 func (c *Checksum) checksum(files ...string) (string, error) {
 	h := md5.New()
 
@@ -73,6 +77,11 @@ func (c *Checksum) checksum(files ...string) (string, error) {
 	return fmt.Sprintf("%x", h.Sum(nil)), nil
 }
 
+// Value implements the Chcker Interface
+func (c *Checksum) Value() (string, error) {
+	return c.checksum()
+}
+
 // OnError implements the Checker interface
 func (c *Checksum) OnError() error {
 	return os.Remove(c.checksumFilePath())

internal/status/none.go

@@ -8,6 +8,15 @@ func (None) IsUpToDate() (bool, error) {
 	return false, nil
 }
 
+// Value implements the Checker interface
+func (None) Value() (string, error) {
+	return "", nil
+}
+
+func (None) Kind() string {
+	return "none"
+}
+
 // OnError implements the Checker interface
 func (None) OnError() error {
 	return nil

internal/status/status.go

@@ -9,5 +9,7 @@ var (
 // Checker is an interface that checks if the status is up-to-date
 type Checker interface {
 	IsUpToDate() (bool, error)
+	Value() (string, error)
 	OnError() error
+	Kind() string
 }

internal/status/timestamp.go

@@ -1,6 +1,7 @@
 package status
 
 import (
+	"fmt"
 	"os"
 	"time"
 )
@@ -41,6 +42,29 @@ func (t *Timestamp) IsUpToDate() (bool, error) {
 	return !generatesMinTime.Before(sourcesMaxTime), nil
 }
 
+func (t *Timestamp) Kind() string {
+	return "timestamp"
+}
+
+// Value implements the Checker Interface
+func (t *Timestamp) Value() (string, error) {
+	sources, err := glob(t.Dir, t.Sources)
+	if err != nil {
+		return "<no value>", err
+	}
+
+	sourcesMaxTime, err := getMaxTime(sources...)
+	if err != nil {
+		return "<no value>", err
+	}
+
+	if sourcesMaxTime.IsZero() {
+		return "0", nil
+	}
+
+	return fmt.Sprintf("%d", sourcesMaxTime.Unix()), nil
+}
+
 func getMinTime(files ...string) (time.Time, error) {
 	var t time.Time
 	for _, f := range files {

status.go

@@ -32,7 +32,7 @@ func (e *Executor) isTaskUpToDate(ctx context.Context, t *taskfile.Task) (bool,
 		return e.isTaskUpToDateStatus(ctx, t)
 	}
 
-	checker, err := e.getStatusChecker(t)
+	checker, err := e.GetStatusChecker(t)
 	if err != nil {
 		return false, err
 	}
@@ -41,14 +41,14 @@ func (e *Executor) isTaskUpToDate(ctx context.Context, t *taskfile.Task) (bool,
 }
 
 func (e *Executor) statusOnError(t *taskfile.Task) error {
-	checker, err := e.getStatusChecker(t)
+	checker, err := e.GetStatusChecker(t)
 	if err != nil {
 		return err
 	}
 	return checker.OnError()
 }
 
-func (e *Executor) getStatusChecker(t *taskfile.Task) (status.Checker, error) {
+func (e *Executor) GetStatusChecker(t *taskfile.Task) (status.Checker, error) {
 	switch t.Method {
 	case "", "timestamp":
 		return &status.Timestamp{

task_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 
 	"github.com/go-task/task/v2"
+	"github.com/go-task/task/v2/internal/logger"
 	"github.com/go-task/task/v2/internal/taskfile"
 
 	"github.com/mitchellh/go-homedir"
@@ -388,12 +389,20 @@ func TestStatusChecksum(t *testing.T) {
 	}
 
 	var buff bytes.Buffer
+
+	logCapturer := logger.Logger{
+		Stdout:  &buff,
+		Stderr:  &buff,
+		Verbose: true,
+	}
+
 	e := task.Executor{
 		Dir:    dir,
 		Stdout: &buff,
 		Stderr: &buff,
 	}
 	assert.NoError(t, e.Setup())
+	e.Logger = &logCapturer
 
 	assert.NoError(t, e.Run(context.Background(), taskfile.Call{Task: "build"}))
 	for _, f := range files {
@@ -404,6 +413,18 @@ func TestStatusChecksum(t *testing.T) {
 	buff.Reset()
 	assert.NoError(t, e.Run(context.Background(), taskfile.Call{Task: "build"}))
 	assert.Equal(t, `task: Task "build" is up to date`+"\n", buff.String())
+
+	buff.Reset()
+	e.Silent = false
+	e.Verbose = true
+	assert.NoError(t, e.Run(context.Background(), taskfile.Call{Task: "build-with-checksum"}))
+	assert.Contains(t, buff.String(), "d41d8cd98f00b204e9800998ecf8427e")
+
+	buff.Reset()
+	inf, _ := os.Stat(filepath.Join(dir, "source.txt"))
+	ts := fmt.Sprintf("%d", inf.ModTime().Unix())
+	assert.NoError(t, e.Run(context.Background(), taskfile.Call{Task: "build-with-timestamp"}))
+	assert.Contains(t, buff.String(), ts)
 }
 
 func TestInit(t *testing.T) {

testdata/checksum/Taskfile.yml

@@ -7,3 +7,16 @@ build:
   generates:
     - ./generated.txt
   method: checksum
+
+build-with-checksum:
+  sources:
+    - ./source.txt
+  method: checksum
+  status:
+    - echo "{{.CHECKSUM}}"
+
+build-with-timestamp:
+  sources:
+    - ./source.txt
+  status:
+    - echo "{{.TIMESTAMP}}"

variables.go

@@ -1,7 +1,9 @@
 package task
 
 import (
+	"io/ioutil"
 	"path/filepath"
+	"strings"
 
 	"github.com/go-task/task/v2/internal/execext"
 	"github.com/go-task/task/v2/internal/taskfile"
@@ -20,6 +22,7 @@ func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	r := templater.Templater{Vars: vars}
 
 	new := taskfile.Task{
@@ -27,7 +30,6 @@ func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
 		Desc:        r.Replace(origTask.Desc),
 		Sources:     r.ReplaceSlice(origTask.Sources),
 		Generates:   r.ReplaceSlice(origTask.Generates),
-		Status:      r.ReplaceSlice(origTask.Status),
 		Dir:         r.Replace(origTask.Dir),
 		Vars:        nil,
 		Env:         nil,
@@ -62,6 +64,31 @@ func (e *Executor) CompiledTask(call taskfile.Call) (*taskfile.Task, error) {
 		new.Env[k] = taskfile.Var{Static: static}
 	}
 
+	if len(origTask.Status) > 0 {
+
+		e := &Executor{
+			Dir:    new.Dir,
+			Stdout: ioutil.Discard,
+			Stderr: ioutil.Discard,
+			Dry:    true,
+		}
+
+		checker, err := e.GetStatusChecker(&new)
+		if err != nil {
+			return nil, err
+		}
+
+		value, err := checker.Value()
+		if err != nil {
+			return nil, err
+		}
+
+		vars[strings.ToUpper(checker.Kind())] = taskfile.Var{Static: value}
+
+		statusTemplater := templater.Templater{Vars: vars}
+		new.Status = statusTemplater.ReplaceSlice(origTask.Status)
+	}
+
 	if len(origTask.Cmds) > 0 {
 		new.Cmds = make([]*taskfile.Cmd, len(origTask.Cmds))
 		for i, cmd := range origTask.Cmds {