273: PR bot should check for empty pull request body

bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java

@@ -135,6 +135,11 @@ private Optional<MergeSource> mergeSource() {
     private List<String> botSpecificChecks() throws IOException {
         var ret = new ArrayList<String>();
 
+        if (bodyWithoutStatus().isBlank()) {
+            var error = "The pull request body must not be empty.";
+            ret.add(error);
+        }
+
         if (!isTargetBranchAllowed()) {
             var error = "The branch `" + pr.targetRef() + "` is not allowed as target branch. The allowed target branches are:\n" +
                     allowedTargetBranches().stream()
@@ -365,6 +370,14 @@ private String checkoutCommands() {
            "`$ git checkout pull/" + pr.id() + "`\n";
     }
 
+    private String bodyWithoutStatus() {
+        var description = pr.body();
+        var markerIndex = description.lastIndexOf(progressMarker);
+        return (markerIndex < 0 ?
+                description :
+                description.substring(0, markerIndex)).trim();
+    }
+
     private String updateStatusMessage(String message) {
         var description = pr.body();
         var markerIndex = description.lastIndexOf(progressMarker);
@@ -373,9 +386,7 @@ private String updateStatusMessage(String message) {
             log.info("Progress already up to date");
             return description;
         }
-        var newBody = (markerIndex < 0 ?
-                description :
-                description.substring(0, markerIndex)).trim() + "\n" + progressMarker + "\n" + message;
+        var newBody = bodyWithoutStatus() + "\n" + progressMarker + "\n" + message;
 
         // TODO? Retrieve the body again here to lower the chance of concurrent updates
         pr.setBody(newBody);

bots/pr/src/test/java/org/openjdk/skara/bots/pr/CheckTests.java

@@ -654,6 +654,56 @@ void blockingLabel(TestInfo testInfo) throws IOException {
         }
     }
 
+    @Test
+    void emptyPRBody(TestInfo testInfo) throws IOException {
+        try (var credentials = new HostCredentials(testInfo);
+             var tempFolder = new TemporaryDirectory()) {
+            var author = credentials.getHostedRepository();
+            var reviewer = credentials.getHostedRepository();
+
+            var censusBuilder = credentials.getCensusBuilder()
+                                           .addAuthor(author.forge().currentUser().id())
+                                           .addReviewer(reviewer.forge().currentUser().id());
+            var checkBot = PullRequestBot.newBuilder()
+                                         .repo(author)
+                                         .censusRepo(censusBuilder.build())
+                                         .build();
+
+            // Populate the projects repository
+            var localRepo = CheckableRepository.init(tempFolder.path(), author.repositoryType());
+            var masterHash = localRepo.resolve("master").orElseThrow();
+            localRepo.push(masterHash, author.url(), "master", true);
+
+            // Make a change with a corresponding PR
+            var editHash = CheckableRepository.appendAndCommit(localRepo);
+            localRepo.push(editHash, author.url(), "edit", true);
+            var pr = credentials.createPullRequest(author, "master", "edit", "Another PR");
+            pr.setBody("    ");
+
+            // Check the status
+            TestBotRunner.runPeriodicItems(checkBot);
+
+            // Verify that the check failed
+            var checks = pr.checks(editHash);
+            assertEquals(1, checks.size());
+            var check = checks.get("jcheck");
+            assertEquals(CheckStatus.FAILURE, check.status());
+            assertTrue(check.summary().orElseThrow().contains("The pull request body must not be empty."));
+
+            // The PR should not yet be ready for review
+            assertFalse(pr.labels().contains("rfr"));
+            assertFalse(pr.labels().contains("ready"));
+
+            // Check the status again
+            pr.setBody("Here's that body");
+            TestBotRunner.runPeriodicItems(checkBot);
+
+            // The PR should now be ready for review
+            assertTrue(pr.labels().contains("rfr"));
+            assertFalse(pr.labels().contains("ready"));
+        }
+    }
+
     @Test
     void missingReadyLabel(TestInfo testInfo) throws IOException {
         try (var credentials = new HostCredentials(testInfo);

test/src/main/java/org/openjdk/skara/test/HostCredentials.java

@@ -355,7 +355,7 @@ public IssueProject getIssueProject() {
     }
 
     public PullRequest createPullRequest(HostedRepository hostedRepository, String targetRef, String sourceRef, String title, boolean draft) {
-        var pr = hostedRepository.createPullRequest(hostedRepository, targetRef, sourceRef, title, List.of(), draft);
+        var pr = hostedRepository.createPullRequest(hostedRepository, targetRef, sourceRef, title, List.of("PR body"), draft);
         pullRequestsToBeClosed.add(pr);
         return pr;
     }