bugfix(declarative): Stage with any 2 of parallel, steps, matrix, stages should throw error

src/main/groovy/com/lesfurets/jenkins/unit/declarative/StageDeclaration.groovy

@@ -42,9 +42,24 @@ class StageDeclaration extends GenericPipelineDeclaration {
 
     def execute(Object delegate) {
         String name = this.name
+        def actions = 0
+        if(parallel) {
+            actions++
+        }
+        if(stages.size()>0) {
+            actions++
+        }
+        if(steps) {
+            actions++
+        }
+        if (actions > 1 ) {
+            throw new IllegalArgumentException ("""Only one of "matrix", "parallel", "stages", or "steps" allowed for stage "${name}" """)
+        }
+
         this.options.each {
             executeOn(delegate, it)
         }
+
         if(parallel) {
             parallel.execute(delegate)
         }
@@ -56,15 +71,20 @@ class StageDeclaration extends GenericPipelineDeclaration {
 
         if (!when || when.execute(delegate)) {
             super.execute(delegate)
+
             // TODO handle credentials
+
+            Closure stageBody = { agent?.execute(delegate) }
+            Closure cl = { stage("$name", stageBody) }
+            if(steps) {
+                stageBody =  stageBody >> steps.rehydrate(delegate, this, delegate)
+            }
+            executeWith(delegate, cl)
+
             this.stages.entrySet().forEach { e ->
                 e.value.execute(delegate)
             }
-            if(steps) {
-                Closure stageBody = { agent?.execute(delegate) } >> steps.rehydrate(delegate, this, delegate)
-                Closure cl = { stage("$name", stageBody) }
-                executeWith(delegate, cl)
-            }
+
             if (post) {
                 this.post.execute(delegate)
             }

src/test/groovy/com/lesfurets/jenkins/unit/declarative/TestDeclarativePipeline.groovy

@@ -765,4 +765,30 @@ class TestDeclarativePipeline extends DeclarativePipelineTest {
         printCallStack()
         assertCallStack().contains('writeFile({file=messages/messages.msg, text=text})')
     }
+
+    @Test void test_agent_in_stage_with_no_steps() {
+        runScript("AgentStageNoSteps_Jenkinsfile")
+        assertJobStatusSuccess()
+
+        assertCallStack().contains('post A')
+        assertCallStack().contains('post B')
+        assertCallStack().contains('post C')
+
+        assertCallStack().contains('echo(A)')
+        assertCallStack().contains('echo(C)')
+        assertCallStack().contains('stage(A, groovy.lang.Closure)')
+        assertCallStack().contains('stage(C, groovy.lang.Closure)')
+        assertCallStack().contains('labelA')
+        assertCallStack().contains('labelC')
+        // assertion bellow would fail
+        assertCallStack().contains('stage(B, groovy.lang.Closure)')
+        assertCallStack().contains('labelB')
+
+    }
+
+    @Test(expected = IllegalArgumentException)
+    void test_stage_and_steps() {
+        runScript("StageAndSteps_Jenkinsfile")
+    }
 }
+

src/test/jenkins/jenkinsfiles/AgentStageNoSteps_Jenkinsfile

@@ -0,0 +1,25 @@
+pipeline {
+    agent none
+    stages {
+        stage('A') {
+            agent { label 'labelA' }
+            post { always {echo 'post A'}}
+            steps {
+                echo 'A'
+            }
+        }
+        stage('B') {
+            agent {label 'labelB'}
+            post { always {echo 'post B'}}
+            stages {
+                stage('C') {
+                    agent {label 'labelC'}
+                    post { always {echo 'post C'}}
+                    steps {
+                        echo 'C'
+                    }
+                }
+            }
+        }
+    }
+}

src/test/jenkins/jenkinsfiles/StageAndSteps_Jenkinsfile

@@ -0,0 +1,19 @@
+pipeline {
+    agent none
+    stages {
+        stage('B') {
+            agent {label 'labelB'}
+            post { always {echo 'post B'}}
+            steps { echo 'B' }
+            stages {
+                stage('C') {
+                    agent {label 'labelC'}
+                    post { always {echo 'post C'}}
+                    steps {
+                        echo 'C'
+                    }
+                }
+            }
+        }
+    }
+}