Add depends_on support for steps

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
+
+  deploy:
+    image: plugins/docker
+    settings:
+      repo: foo/bar
++    depends_on: [build, test] # deploy will be executed after build and test finished
 
-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.
+  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