Fix "null" string literal in steps that no exception text

src/main/frontend/common/RestClient.tsx

@@ -118,6 +118,7 @@ export async function getExceptionText(stepId: string): Promise<string[]> {
     const response = await fetch(`exceptionText?nodeId=${stepId}`);
     if (!response.ok) throw response.statusText;
     const text = await response.text();
+    if (!text) return [];
     return text.split("\n");
   } catch (e) {
     console.error(`Caught error when fetching console: '${e}'`);

src/main/java/io/jenkins/plugins/pipelinegraphview/consoleview/PipelineConsoleViewAction.java

@@ -185,7 +185,8 @@
         run.checkPermission(Item.READ);
         String nodeId = req.getParameter("nodeId");
         if (nodeId == null) return HttpResponses.error(400, "missing ?nodeId");
-        return HttpResponses.text(getNodeExceptionText(nodeId));
+        String exceptionText = getNodeExceptionText(nodeId);
+        return HttpResponses.text(exceptionText != null ? exceptionText : "");
     }
 
     private AnnotatedLargeText<? extends FlowNode> getLogForNode(String nodeId) throws IOException {

src/test/java/io/jenkins/plugins/pipelinegraphview/PipelineGraphViewTest.java

@@ -164,4 +164,42 @@ void searchOffScreen(Page p, JenkinsConfiguredWithCodeRule j) throws Exception {
                 .scrollToText("Hello, world 1000!")
                 .scrollToText("Hello, world 1!");
     }
+
+    @Test
+    @ConfiguredWithCode("configure-appearance.yml")
+    void errorWithMessage(Page p, JenkinsConfiguredWithCodeRule j) throws Exception {
+        String name = "gh1169";
+        WorkflowRun run = TestUtils.createAndRunJob(j, name, "gh1169_errorWithMessage.jenkinsfile", Result.FAILURE);
+
+        // Note that the locator used in stageHasSteps accumulates the error step's message text content into the found
+        // step name so we just check that instead of also calling stepContainText
+        new PipelineJobPage(p, run.getParent())
+                .goTo()
+                .hasBuilds(1)
+                .nthBuild(0)
+                .goToBuild()
+                .goToPipelineOverview()
+                .hasStagesInGraph(1, "Stage")
+                .selectStageInGraph("Stage")
+                .stageHasSteps("Error signalError");
+    }
+
+    @Issue("GH#1169")
+    @Test
+    @ConfiguredWithCode("configure-appearance.yml")
+    void errorWithNoMessage(Page p, JenkinsConfiguredWithCodeRule j) throws Exception {
+        String name = "gh1169";
+        WorkflowRun run = TestUtils.createAndRunJob(j, name, "gh1169_errorWithNoMessage.jenkinsfile", Result.FAILURE);
+
+        new PipelineJobPage(p, run.getParent())
+                .goTo()
+                .hasBuilds(1)
+                .nthBuild(0)
+                .goToBuild()
+                .goToPipelineOverview()
+                .hasStagesInGraph(1, "Stage")
+                .selectStageInGraph("Stage")
+                .stageHasSteps("Error signal")
+                .stepDoesNotContainText("Error signal", "null");
+    }
 }

src/test/java/io/jenkins/plugins/pipelinegraphview/playwright/PipelineConsole.java

@@ -77,6 +77,28 @@ public void stepContainsText(String stepName, String textToFind) {
         }
     }
 
+    public void stepDoesNotContainText(String stepName, String textToNotFind) {
+        log.info("Checking that the step {} does not contain a log with the text {}", stepName, textToNotFind);
+
+        Locator stepContainer = steps().filter(new Locator.FilterOptions()
+                        .setHas(page.locator(
+                                STEP_NAME_CLASS,
+                                new Page.LocatorOptions().setHasText(Pattern.compile("^" + stepName + "$")))))
+                .first();
+
+        if (!isOpenStep(stepContainer)) {
+            stepContainer.click();
+        }
+        Locator stepLogs = stepContainer.getByRole(AriaRole.LOG);
+        assertThat(stepLogs).not().containsText(textToNotFind);
+
+        Locator plainTextLogsLink = stepContainer.getByRole(
+                AriaRole.LINK, new Locator.GetByRoleOptions().setName("View step as plain text"));
+        try (Page plainText = page.context().waitForPage(plainTextLogsLink::click)) {
+            assertThat(plainText.locator("body")).not().containsText(textToNotFind);
+        }
+    }
+
     public void stageHasSteps(String step, String... additional) {
         List<String> expectedSteps = new ArrayList<>();
         expectedSteps.add(step);

src/test/java/io/jenkins/plugins/pipelinegraphview/playwright/PipelineOverviewPage.java

@@ -85,6 +85,11 @@ public PipelineOverviewPage stepContainsText(String stepName, String textToFind)
         return this;
     }
 
+    public PipelineOverviewPage stepDoesNotContainText(String stepName, String textToNotFind) {
+        logs.stepDoesNotContainText(stepName, textToNotFind);
+        return this;
+    }
+
     public PipelineOverviewPage stageHasSteps(String step, String... additional) {
         logs.stageHasSteps(step, additional);
         return this;

src/test/resources/io/jenkins/plugins/pipelinegraphview/utils/gh1169_errorWithMessage.jenkinsfile

@@ -0,0 +1,3 @@
+stage("Stage") {
+    error("Error")
+}

src/test/resources/io/jenkins/plugins/pipelinegraphview/utils/gh1169_errorWithNoMessage.jenkinsfile

@@ -0,0 +1,3 @@
+stage("Stage") {
+    error()
+}