Add depends_on support for steps (#2771)

Co-authored-by: 6543 <6543@obermui.de>

cli/lint/lint.go

@@ -101,7 +101,7 @@ func lintFile(_ *cli.Context, file string) error {
 	// TODO: lint multiple files at once to allow checks for sth like "depends_on" to work
 	err = linter.New(linter.WithTrusted(true)).Lint([]*linter.WorkflowConfig{config})
 	if err != nil {
-		fmt.Printf("🔥 %s has warning / errors:\n", output.String(config.File).Underline())
+		fmt.Printf("🔥 %s has warnings / errors:\n", output.String(config.File).Underline())
 
 		hasErrors := false
 		for _, err := range pipeline_errors.GetPipelineErrors(err) {

docs/docs/20-usage/20-workflow-syntax.md

@@ -443,33 +443,28 @@ when:
   - evaluate: 'SKIP != "true"'
 ```
 
-### `group` - Parallel execution
+### `depends_on`
 
-Woodpecker supports parallel step execution for same-machine fan-in and fan-out. Parallel steps are configured using the `group` attribute. This instructs the agent to execute the named group in parallel.
-
-Example parallel configuration:
+Normally steps of a workflow are executed serially in the order in which they are defined. As soon as you set `depends_on` for a step a [directed acyclic graph](https://en.wikipedia.org/wiki/Directed_acyclic_graph) will be used and all steps of the workflow will be executed in parallel besides the steps that have a dependency set to another step using `depends_on`:
 
 ```diff
  steps:
-   backend:
-+    group: build
-     image: golang
-     commands:
-       - go build
-       - go test
-   frontend:
-+    group: build
-     image: node
-     commands:
-       - npm install
-       - npm run test
-       - npm run build
-   publish:
-     image: plugins/docker
-     repo: octocat/hello-world
-```
+  build: # build will be executed immediately
+    image: golang
+    commands:
+      - go build
 
-In the above example, the `frontend` and `backend` steps are executed in parallel. The agent will not execute the `publish` step until the group completes.
+  deploy:
+    image: plugins/docker
+    settings:
+      repo: foo/bar
++    depends_on: [build, test] # deploy will be executed after build and test finished
+
+  test: # test will be executed immediately as no dependencies are set
+    image: golang
+    commands:
+      - go test
+```
 
 ### `volumes`
 

docs/docs/91-migrations.md

@@ -4,6 +4,7 @@ Some versions need some changes to the server configuration or the pipeline conf
 
 ## `next`
 
+- Deprecated `steps.[name].group` in favor of `steps.[name].depends_on` (see [workflow syntax](./20-usage/20-workflow-syntax.md#depends_on) to learn how to set dependencies)
 - Removed `WOODPECKER_ROOT_PATH` and `WOODPECKER_ROOT_URL` config variables. Use `WOODPECKER_HOST` with a path instead
 - Pipelines without a config file will now be skipped instead of failing
 

pipeline/frontend/yaml/compiler/compiler.go

@@ -233,10 +233,9 @@ func (c *Compiler) Compile(conf *yaml_types.Workflow) (*backend_types.Config, er
 		config.Stages = append(config.Stages, stage)
 	}
 
-	// add pipeline steps. 1 pipeline step per stage, at the moment
-	var stage *backend_types.Stage
-	var group string
-	for i, container := range conf.Steps.ContainerList {
+	// add pipeline steps
+	steps := make([]*dagCompilerStep, 0, len(conf.Steps.ContainerList))
+	for pos, container := range conf.Steps.ContainerList {
 		// Skip if local and should not run local
 		if c.local && !container.When.IsLocal() {
 			continue
@@ -248,16 +247,7 @@ func (c *Compiler) Compile(conf *yaml_types.Workflow) (*backend_types.Config, er
 			return nil, err
 		}
 
-		if stage == nil || group != container.Group || container.Group == "" {
-			group = container.Group
-
-			stage = new(backend_types.Stage)
-			stage.Name = fmt.Sprintf("%s_stage_%v", c.prefix, i)
-			stage.Alias = container.Name
-			config.Stages = append(config.Stages, stage)
-		}
-
-		name := fmt.Sprintf("%s_step_%d", c.prefix, i)
+		name := fmt.Sprintf("%s_step_%d", c.prefix, pos)
 		stepType := backend_types.StepTypeCommands
 		if container.IsPlugin() {
 			stepType = backend_types.StepTypePlugin
@@ -274,9 +264,23 @@ func (c *Compiler) Compile(conf *yaml_types.Workflow) (*backend_types.Config, er
 			}
 		}
 
-		stage.Steps = append(stage.Steps, step)
+		steps = append(steps, &dagCompilerStep{
+			step:      step,
+			position:  pos,
+			name:      container.Name,
+			group:     container.Group,
+			dependsOn: container.DependsOn,
+		})
 	}
 
+	// generate stages out of steps
+	stepStages, err := newDAGCompiler(steps, c.prefix).compile()
+	if err != nil {
+		return nil, err
+	}
+
+	config.Stages = append(config.Stages, stepStages...)
+
 	err = c.setupCacheRebuild(conf, config)
 	if err != nil {
 		return nil, err

pipeline/frontend/yaml/compiler/compiler_test.go

@@ -99,120 +99,199 @@ func TestCompilerCompile(t *testing.T) {
 		fronConf    *yaml_types.Workflow
 		backConf    *backend_types.Config
 		expectedErr string
-	}{{
-		name:     "empty workflow, no clone",
-		fronConf: &yaml_types.Workflow{SkipClone: true},
-		backConf: &backend_types.Config{
-			Networks: defaultNetworks,
-			Volumes:  defaultVolumes,
+	}{
+		{
+			name:     "empty workflow, no clone",
+			fronConf: &yaml_types.Workflow{SkipClone: true},
+			backConf: &backend_types.Config{
+				Networks: defaultNetworks,
+				Volumes:  defaultVolumes,
+			},
 		},
-	}, {
-		name:     "empty workflow, default clone",
-		fronConf: &yaml_types.Workflow{},
-		backConf: &backend_types.Config{
-			Networks: defaultNetworks,
-			Volumes:  defaultVolumes,
-			Stages:   []*backend_types.Stage{defaultCloneStage},
+		{
+			name:     "empty workflow, default clone",
+			fronConf: &yaml_types.Workflow{},
+			backConf: &backend_types.Config{
+				Networks: defaultNetworks,
+				Volumes:  defaultVolumes,
+				Stages:   []*backend_types.Stage{defaultCloneStage},
+			},
 		},
-	}, {
-		name: "workflow with one dummy step",
-		fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
-			Name:  "dummy",
-			Image: "dummy_img",
-		}}}},
-		backConf: &backend_types.Config{
-			Networks: defaultNetworks,
-			Volumes:  defaultVolumes,
-			Stages: []*backend_types.Stage{defaultCloneStage, {
-				Name:  "test_stage_0",
-				Alias: "dummy",
-				Steps: []*backend_types.Step{{
-					Name:       "test_step_0",
-					Alias:      "dummy",
-					Type:       backend_types.StepTypePlugin,
-					Image:      "dummy_img",
-					OnSuccess:  true,
-					Failure:    "fail",
-					Volumes:    []string{defaultVolumes[0].Name + ":"},
-					Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"dummy"}}},
-					ExtraHosts: []backend_types.HostAlias{},
+		{
+			name: "workflow with one dummy step",
+			fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
+				Name:  "dummy",
+				Image: "dummy_img",
+			}}}},
+			backConf: &backend_types.Config{
+				Networks: defaultNetworks,
+				Volumes:  defaultVolumes,
+				Stages: []*backend_types.Stage{defaultCloneStage, {
+					Name:  "test_stage_0",
+					Alias: "dummy",
+					Steps: []*backend_types.Step{{
+						Name:       "test_step_0",
+						Alias:      "dummy",
+						Type:       backend_types.StepTypePlugin,
+						Image:      "dummy_img",
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"dummy"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}},
 				}},
-			}},
+			},
 		},
-	}, {
-		name: "workflow with three steps and one group",
-		fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
-			Name:     "echo env",
-			Image:    "bash",
-			Commands: []string{"env"},
-		}, {
-			Name:     "parallel echo 1",
-			Group:    "parallel",
-			Image:    "bash",
-			Commands: []string{"echo 1"},
-		}, {
-			Name:     "parallel echo 2",
-			Group:    "parallel",
-			Image:    "bash",
-			Commands: []string{"echo 2"},
-		}}}},
-		backConf: &backend_types.Config{
-			Networks: defaultNetworks,
-			Volumes:  defaultVolumes,
-			Stages: []*backend_types.Stage{defaultCloneStage, {
-				Name:  "test_stage_0",
-				Alias: "echo env",
-				Steps: []*backend_types.Step{{
-					Name:       "test_step_0",
-					Alias:      "echo env",
-					Type:       backend_types.StepTypeCommands,
-					Image:      "bash",
-					Commands:   []string{"env"},
-					OnSuccess:  true,
-					Failure:    "fail",
-					Volumes:    []string{defaultVolumes[0].Name + ":"},
-					Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"echo env"}}},
-					ExtraHosts: []backend_types.HostAlias{},
-				}},
+		{
+			name: "workflow with three steps and one group",
+			fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
+				Name:     "echo env",
+				Image:    "bash",
+				Commands: []string{"env"},
 			}, {
-				Name:  "test_stage_1",
-				Alias: "parallel echo 1",
-				Steps: []*backend_types.Step{{
-					Name:       "test_step_1",
-					Alias:      "parallel echo 1",
-					Type:       backend_types.StepTypeCommands,
-					Image:      "bash",
-					Commands:   []string{"echo 1"},
-					OnSuccess:  true,
-					Failure:    "fail",
-					Volumes:    []string{defaultVolumes[0].Name + ":"},
-					Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"parallel echo 1"}}},
-					ExtraHosts: []backend_types.HostAlias{},
+				Name:     "parallel echo 1",
+				Group:    "parallel",
+				Image:    "bash",
+				Commands: []string{"echo 1"},
+			}, {
+				Name:     "parallel echo 2",
+				Group:    "parallel",
+				Image:    "bash",
+				Commands: []string{"echo 2"},
+			}}}},
+			backConf: &backend_types.Config{
+				Networks: defaultNetworks,
+				Volumes:  defaultVolumes,
+				Stages: []*backend_types.Stage{defaultCloneStage, {
+					Name:  "test_stage_0",
+					Alias: "echo env",
+					Steps: []*backend_types.Step{{
+						Name:       "test_step_0",
+						Alias:      "echo env",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"env"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"echo env"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}},
 				}, {
-					Name:       "test_step_2",
-					Alias:      "parallel echo 2",
-					Type:       backend_types.StepTypeCommands,
-					Image:      "bash",
-					Commands:   []string{"echo 2"},
-					OnSuccess:  true,
-					Failure:    "fail",
-					Volumes:    []string{defaultVolumes[0].Name + ":"},
-					Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"parallel echo 2"}}},
-					ExtraHosts: []backend_types.HostAlias{},
+					Name:  "test_stage_1",
+					Alias: "parallel echo 1",
+					Steps: []*backend_types.Step{{
+						Name:       "test_step_1",
+						Alias:      "parallel echo 1",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"echo 1"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"parallel echo 1"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}, {
+						Name:       "test_step_2",
+						Alias:      "parallel echo 2",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"echo 2"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"parallel echo 2"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}},
 				}},
-			}},
+			},
 		},
-	}, {
-		name: "workflow with missing secret",
-		fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
-			Name:     "step",
-			Image:    "bash",
-			Commands: []string{"env"},
-			Secrets:  yaml_types.Secrets{Secrets: []*yaml_types.Secret{{Source: "missing", Target: "missing"}}},
-		}}}},
-		backConf:    nil,
-		expectedErr: "secret \"missing\" not found or not allowed to be used",
-	}}
+		{
+			name: "workflow with three steps and depends_on",
+			fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
+				Name:     "echo env",
+				Image:    "bash",
+				Commands: []string{"env"},
+			}, {
+				Name:      "echo 1",
+				Image:     "bash",
+				Commands:  []string{"echo 1"},
+				DependsOn: []string{"echo env", "echo 2"},
+			}, {
+				Name:     "echo 2",
+				Image:    "bash",
+				Commands: []string{"echo 2"},
+			}}}},
+			backConf: &backend_types.Config{
+				Networks: defaultNetworks,
+				Volumes:  defaultVolumes,
+				Stages: []*backend_types.Stage{defaultCloneStage, {
+					Name:  "test_stage_0",
+					Alias: "test_stage_0",
+					Steps: []*backend_types.Step{{
+						Name:       "test_step_0",
+						Alias:      "echo env",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"env"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"echo env"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}, {
+						Name:       "test_step_2",
+						Alias:      "echo 2",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"echo 2"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"echo 2"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}},
+				}, {
+					Name:  "test_stage_1",
+					Alias: "test_stage_1",
+					Steps: []*backend_types.Step{{
+						Name:       "test_step_1",
+						Alias:      "echo 1",
+						Type:       backend_types.StepTypeCommands,
+						Image:      "bash",
+						Commands:   []string{"echo 1"},
+						OnSuccess:  true,
+						Failure:    "fail",
+						Volumes:    []string{defaultVolumes[0].Name + ":"},
+						Networks:   []backend_types.Conn{{Name: "test_default", Aliases: []string{"echo 1"}}},
+						ExtraHosts: []backend_types.HostAlias{},
+					}},
+				}},
+			},
+		},
+		{
+			name: "workflow with missing secret",
+			fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
+				Name:     "step",
+				Image:    "bash",
+				Commands: []string{"env"},
+				Secrets:  yaml_types.Secrets{Secrets: []*yaml_types.Secret{{Source: "missing", Target: "missing"}}},
+			}}}},
+			backConf:    nil,
+			expectedErr: "secret \"missing\" not found or not allowed to be used",
+		},
+		{
+			name: "workflow with broken step dependency",
+			fronConf: &yaml_types.Workflow{Steps: yaml_types.ContainerList{ContainerList: []*yaml_types.Container{{
+				Name:      "dummy",
+				Image:     "dummy_img",
+				DependsOn: []string{"not exist"},
+			}}}},
+			backConf:    nil,
+			expectedErr: "step 'dummy' depends on unknown step 'not exist'",
+		},
+	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {

pipeline/frontend/yaml/compiler/dag.go

@@ -0,0 +1,159 @@
+// Copyright 2023 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package compiler
+
+import (
+	"fmt"
+
+	backend_types "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
+)
+
+type dagCompilerStep struct {
+	step      *backend_types.Step
+	position  int
+	name      string
+	group     string
+	dependsOn []string
+}
+
+type dagCompiler struct {
+	steps  []*dagCompilerStep
+	prefix string
+}
+
+func newDAGCompiler(steps []*dagCompilerStep, prefix string) dagCompiler {
+	return dagCompiler{
+		steps:  steps,
+		prefix: prefix,
+	}
+}
+
+func (c dagCompiler) isDAG() bool {
+	for _, v := range c.steps {
+		if len(v.dependsOn) != 0 {
+			return true
+		}
+	}
+	return false
+}
+
+func (c dagCompiler) compile() ([]*backend_types.Stage, error) {
+	if c.isDAG() {
+		return c.compileByDependsOn()
+	}
+	return c.compileByGroup()
+}
+
+func (c dagCompiler) compileByGroup() ([]*backend_types.Stage, error) {
+	stages := make([]*backend_types.Stage, 0, len(c.steps))
+	var currentStage *backend_types.Stage
+	var currentGroup string
+
+	for _, s := range c.steps {
+		// create a new stage if current step is in a new group compared to last one
+		if currentStage == nil || currentGroup != s.group || s.group == "" {
+			currentGroup = s.group
+
+			currentStage = new(backend_types.Stage)
+			currentStage.Name = fmt.Sprintf("%s_stage_%v", c.prefix, s.position)
+			currentStage.Alias = s.name
+			stages = append(stages, currentStage)
+		}
+
+		// add step to current stage
+		currentStage.Steps = append(currentStage.Steps, s.step)
+	}
+
+	return stages, nil
+}
+
+func (c dagCompiler) compileByDependsOn() ([]*backend_types.Stage, error) {
+	stepMap := make(map[string]*dagCompilerStep, len(c.steps))
+	for _, s := range c.steps {
+		stepMap[s.name] = s
+	}
+	return convertDAGToStages(stepMap, c.prefix)
+}
+
+func dfsVisit(steps map[string]*dagCompilerStep, name string, visited map[string]struct{}, path []string) error {
+	if _, ok := visited[name]; ok {
+		return &ErrStepDependencyCycle{path: path}
+	}
+
+	visited[name] = struct{}{}
+	path = append(path, name)
+
+	for _, dep := range steps[name].dependsOn {
+		if err := dfsVisit(steps, dep, visited, path); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func convertDAGToStages(steps map[string]*dagCompilerStep, prefix string) ([]*backend_types.Stage, error) {
+	addedSteps := make(map[string]struct{})
+	stages := make([]*backend_types.Stage, 0)
+
+	for name, step := range steps {
+		// check if all depends_on are valid
+		for _, dep := range step.dependsOn {
+			if _, ok := steps[dep]; !ok {
+				return nil, &ErrStepMissingDependency{name: name, dep: dep}
+			}
+		}
+
+		// check if there are cycles
+		visited := make(map[string]struct{})
+		if err := dfsVisit(steps, name, visited, []string{}); err != nil {
+			return nil, err
+		}
+	}
+
+	for len(steps) > 0 {
+		addedNodesThisLevel := make(map[string]struct{})
+		stage := &backend_types.Stage{
+			Name:  fmt.Sprintf("%s_stage_%d", prefix, len(stages)),
+			Alias: fmt.Sprintf("%s_stage_%d", prefix, len(stages)),
+		}
+
+		for name, step := range steps {
+			if allDependenciesSatisfied(step, addedSteps) {
+				stage.Steps = append(stage.Steps, step.step)
+				addedNodesThisLevel[name] = struct{}{}
+				delete(steps, name)
+			}
+		}
+
+		for name := range addedNodesThisLevel {
+			addedSteps[name] = struct{}{}
+		}
+
+		stages = append(stages, stage)
+	}
+
+	return stages, nil
+}
+
+func allDependenciesSatisfied(step *dagCompilerStep, addedSteps map[string]struct{}) bool {
+	for _, childName := range step.dependsOn {
+		_, ok := addedSteps[childName]
+		if !ok {
+			return false
+		}
+	}
+	return true
+}

pipeline/frontend/yaml/compiler/dag_test.go

@@ -0,0 +1,62 @@
+// Copyright 2023 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package compiler
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	backend_types "go.woodpecker-ci.org/woodpecker/v2/pipeline/backend/types"
+)
+
+func TestConvertDAGToStages(t *testing.T) {
+	steps := map[string]*dagCompilerStep{
+		"step1": {
+			step:      &backend_types.Step{},
+			dependsOn: []string{"step3"},
+		},
+		"step2": {
+			step:      &backend_types.Step{},
+			dependsOn: []string{"step1"},
+		},
+		"step3": {
+			step:      &backend_types.Step{},
+			dependsOn: []string{"step2"},
+		},
+	}
+	_, err := convertDAGToStages(steps, "")
+	assert.ErrorIs(t, err, &ErrStepDependencyCycle{})
+
+	steps = map[string]*dagCompilerStep{
+		"step1": {
+			step:      &backend_types.Step{},
+			dependsOn: []string{"step2"},
+		},
+		"step2": {
+			step: &backend_types.Step{},
+		},
+	}
+	_, err = convertDAGToStages(steps, "")
+	assert.NoError(t, err)
+
+	steps = map[string]*dagCompilerStep{
+		"step1": {
+			step:      &backend_types.Step{},
+			dependsOn: []string{"not-existing-step"},
+		},
+	}
+	_, err = convertDAGToStages(steps, "")
+	assert.ErrorIs(t, err, &ErrStepMissingDependency{})
+}

pipeline/frontend/yaml/compiler/errors.go

@@ -28,3 +28,30 @@ func (*ErrExtraHostFormat) Is(target error) bool {
 	_, ok := target.(*ErrExtraHostFormat) //nolint:errorlint
 	return ok
 }
+
+type ErrStepMissingDependency struct {
+	name,
+	dep string
+}
+
+func (err *ErrStepMissingDependency) Error() string {
+	return fmt.Sprintf("step '%s' depends on unknown step '%s'", err.name, err.dep)
+}
+
+func (*ErrStepMissingDependency) Is(target error) bool {
+	_, ok := target.(*ErrStepMissingDependency) //nolint:errorlint
+	return ok
+}
+
+type ErrStepDependencyCycle struct {
+	path []string
+}
+
+func (err *ErrStepDependencyCycle) Error() string {
+	return fmt.Sprintf("cycle detected: %v", err.path)
+}
+
+func (*ErrStepDependencyCycle) Is(target error) bool {
+	_, ok := target.(*ErrStepDependencyCycle) //nolint:errorlint
+	return ok
+}

pipeline/frontend/yaml/linter/linter.go

@@ -254,6 +254,21 @@ func (l *Linter) lintDeprecations(config *WorkflowConfig) (err error) {
 		})
 	}
 
+	for _, step := range parsed.Steps.ContainerList {
+		if step.Group != "" {
+			err = multierr.Append(err, &errors.PipelineError{
+				Type:    errors.PipelineErrorTypeDeprecation,
+				Message: "Please use depends_on instead of deprecated 'group' setting",
+				Data: errors.DeprecationErrorData{
+					File:  config.File,
+					Field: "steps." + step.Name + ".group",
+					Docs:  "https://woodpecker-ci.org/docs/next/usage/workflow-syntax#depends_on",
+				},
+				IsWarning: true,
+			})
+		}
+	}
+
 	return err
 }
 

pipeline/frontend/yaml/linter/schema/schema.json

@@ -344,6 +344,12 @@
           "description": "Execute multiple steps with the same group key in parallel. Read more: https://woodpecker-ci.org/docs/usage/pipeline-syntax#step-group---parallel-execution",
           "type": "string"
         },
+        "depends_on": {
+          "description": "Execute a step after another step has finished.",
+          "type": "array",
+          "items": { "type": "string" },
+          "minLength": 1
+        },
         "detach": {
           "description": "Detach a step to run in background until pipeline finishes. Read more: https://woodpecker-ci.org/docs/usage/services#detachment",
           "type": "boolean"

pipeline/frontend/yaml/types/container.go

@@ -48,6 +48,7 @@ type (
 		Volumes        Volumes            `yaml:"volumes,omitempty"`
 		When           constraint.When    `yaml:"when,omitempty"`
 		Ports          []base.StringOrInt `yaml:"ports,omitempty"`
+		DependsOn      base.StringOrSlice `yaml:"depends_on,omitempty"`
 
 		// Docker Specific
 		Privileged bool `yaml:"privileged,omitempty"`

server/grpc/rpc.go

@@ -354,7 +354,7 @@ func (s *RPC) RegisterAgent(ctx context.Context, platform, backend, version stri
 
 func (s *RPC) UnregisterAgent(ctx context.Context) error {
 	agent, err := s.getAgentFromContext(ctx)
-	if agent.OwnerID > 0 {
+	if !agent.IsSystemAgent() {
 		// registered with individual agent token -> do not unregister
 		return nil
 	}