fix: SequenceDiagram: draw activations even without explicit deactivation

cypress/integration/rendering/sequencediagram.spec.js

@@ -231,6 +231,32 @@ context('Sequence diagram', () => {
       `
     );
   });
+  it('should render a sequence diagram with activations even if there are no deactivations', () => {
+    renderGraph(
+        `
+    sequenceDiagram
+      participant a
+      participant b
+      participant c
+      participant d
+      activate d
+      a->>b:halloB
+      activate b
+      b->>+c:halloC
+      c->>+b:back
+      create participant e
+      a-->>e:createE
+      activate e
+      a-->>e:halloE
+      destroy e
+      e->>a:destroyE
+      a-->>d : halloD
+    `,
+        { sequence: { useMaxWidth: false } }
+      );
+    cy.get('rect.activation0').should('have.length', 4);
+    cy.get('rect.activation1').should('have.length', 1);
+    });
   context('font settings', () => {
     it('should render different note fonts when configured', () => {
       imgSnapshotTest(
@@ -517,15 +543,15 @@ context('Sequence diagram', () => {
           participant E
           participant G
 
-          A ->>+ B: Task 1
+          A ->> B: Task 1
           rect rgb(178, 102, 255)
             B ->>+ C: Task 2
             C -->>- B: Return
           end
 
           A ->> D: Task 3
           rect rgb(0, 128, 255)
-            D ->>+ E: Task 4
+            D ->> E: Task 4
             rect rgb(0, 204, 0)
             E ->>+ G: Task 5
             G -->>- E: Return
@@ -548,15 +574,15 @@ context('Sequence diagram', () => {
           participant E
           participant G
 
-          A ->>+ B: Task 1
+          A ->> B: Task 1
           opt this is an opt with a long title that will overflow
             B ->>+ C: Task 2
             C -->>- B: Return
           end
 
           A ->> D: Task 3
           opt this is another opt with a long title that will overflow
-            D ->>+ E: Task 4
+            D ->> E: Task 4
             opt this is a nested opt with a long title that will overflow
             E ->>+ G: Task 5
             G -->>- E: Return
@@ -580,15 +606,15 @@ context('Sequence diagram', () => {
           participant E
           participant G
 
-          A ->>+ B: Task 1
+          A ->> B: Task 1
           opt this is an opt with a long title that will overflow
             B ->>+ C: Task 2
             C -->>- B: Return
           end
 
           A ->> D: Task 3
           opt this is another opt with a long title that will overflow
-            D ->>+ E: Task 4
+            D ->> E: Task 4
             opt this is a nested opt with a long title that will overflow
             E ->>+ G: Task 5
             G -->>- E: Return

packages/mermaid/src/diagrams/sequence/sequenceRenderer.ts

@@ -1050,9 +1050,26 @@ export const draw = async function (_text: string, id: string, _version: string,
   for (const e of messagesToDraw) {
     await drawMessage(diagram, e.messageModel, e.lineStartY, diagObj);
   }
+
+  // all remaining activations in 'bounds' were not drawn, because the 'deactivate' is missing -> draw them from the activation y until the bottom / the destroying of the actor
+  for (const actor of bounds.models.actors) {
+    const notDrawnActivationsForThisActor = actorActivations(actor.name);
+    let stopY = bounds.getVerticalPos();
+    let index = 0;
+    for (const notDrawnActivation of notDrawnActivationsForThisActor) {
+      if (actor.stopy) { // if actor was destroyed -> use it's last y
+        stopY = actor.stopy;
+      }
+
+      svgDraw.drawActivation(diagram, notDrawnActivation, stopY, conf, index);
+      index++;
+    }
+  }
+
   if (conf.mirrorActors) {
     await drawActors(diagram, actors, actorKeys, true);
   }
+
   backgrounds.forEach((e) => svgDraw.drawBackgroundRect(diagram, e));
   fixLifeLineHeights(diagram, actors, actorKeys, conf);
 

packages/mermaid/src/docs/syntax/sequenceDiagram.md

@@ -184,6 +184,8 @@ sequenceDiagram
     John-->>-Alice: I feel great!
 ```
 
+If no deactivation is found for an activated actor, it is still added to the diagram.
+
 ## Notes
 
 It is possible to add notes to a sequence diagram. This is done by the notation