Fix crash when viewing invalid snapshot deltas

Author: pmachapman

src/SIL.XForge.Scripture/ClientApp/src/app/translate/editor/editor-history/history-chooser/history-chooser.component.spec.ts

@@ -1,3 +1,4 @@
+import { HttpErrorResponse } from '@angular/common/http';
 import { SimpleChange } from '@angular/core';
 import { ComponentFixture, fakeAsync, flush, TestBed, tick } from '@angular/core/testing';
 import { NoopAnimationsModule } from '@angular/platform-browser/animations';
@@ -147,6 +148,17 @@ describe('HistoryChooserComponent', () => {
     expect(env.revertHistoryButton).toBeNull();
   }));
 
+  it('should not display the revert history button if snapshot is corrupt', fakeAsync(() => {
+    const env = new TestEnvironment();
+    when(mockedParatextService.getSnapshot('project01', 'MAT', 1, 'date_here')).thenReject(
+      new HttpErrorResponse({ status: 409 })
+    );
+    env.triggerNgOnChanges();
+    env.wait();
+    expect(env.revertHistoryButton).toBeNull();
+    expect(env.component.selectedSnapshot).toBeUndefined();
+  }));
+
   it('should revert to the snapshot', fakeAsync(() => {
     const env = new TestEnvironment();
     when(mockedDialogService.confirm(anything(), anything())).thenResolve(true);

src/SIL.XForge.Scripture/ClientApp/src/app/translate/editor/editor-history/history-chooser/history-chooser.component.ts

@@ -217,6 +217,8 @@ export class HistoryChooserComponent implements AfterViewInit, OnChanges {
         // Remember the snapshot so we can apply it
         this.selectedSnapshot = snapshot;
         this.revisionSelect.emit({ revision, snapshot });
-      });
+      })
+      // On error, do not emit the revision
+      .catch(() => {});
   }
 }

src/SIL.XForge.Scripture/Controllers/ParatextController.cs

@@ -216,6 +216,12 @@ DateTime timestamp
         {
             return Ok(await _paratextService.GetSnapshotAsync(userSecret, projectId, book, chapter, timestamp));
         }
+        catch (ArgumentException e)
+        {
+            // We want to report this exception for further investigation ("The delta is not a document.")
+            _exceptionHandler.ReportException(e);
+            return Conflict();
+        }
         catch (DataNotFoundException)
         {
             return NotFound();

test/SIL.XForge.Scripture.Tests/Controllers/ParatextControllerTests.cs

@@ -315,6 +315,21 @@ public async Task GetRevisionHistoryAsync_Success()
         Assert.IsTrue(historyExists);
     }
 
+    [Test]
+    public async Task GetSnapshotAsync_DeltaIsNotADocument()
+    {
+        // Set up test environment
+        var env = new TestEnvironment();
+        env.ParatextService.GetSnapshotAsync(Arg.Any<UserSecret>(), Project01, Book, Chapter, Timestamp)
+            .Throws(new ArgumentException(@"The delta is not a document."));
+
+        // SUT
+        ActionResult<TextSnapshot> actual = await env.Controller.GetSnapshotAsync(Project01, Book, Chapter, Timestamp);
+
+        env.ExceptionHandler.Received(1).ReportException(Arg.Any<ArgumentException>());
+        Assert.IsInstanceOf<ConflictResult>(actual.Result);
+    }
+
     [Test]
     public async Task GetSnapshotAsync_Forbidden()
     {
@@ -565,14 +580,14 @@ private class TestEnvironment
 
         public TestEnvironment()
         {
-            IExceptionHandler exceptionHandler = Substitute.For<IExceptionHandler>();
+            ExceptionHandler = Substitute.For<IExceptionHandler>();
 
             UserAccessor = Substitute.For<IUserAccessor>();
             UserAccessor.UserId.Returns(User01);
             UserAccessor.SystemRoles.Returns([SystemRole.ServalAdmin]);
 
             MemoryRepository<UserSecret> userSecrets = new MemoryRepository<UserSecret>(
-                new[] { new UserSecret { Id = User01 } }
+                [new UserSecret { Id = User01 }]
             );
 
             MachineProjectService = Substitute.For<IMachineProjectService>();
@@ -600,7 +615,7 @@ public TestEnvironment()
             ProjectService = Substitute.For<ISFProjectService>();
 
             Controller = new ParatextController(
-                exceptionHandler,
+                ExceptionHandler,
                 MachineProjectService,
                 ParatextService,
                 ProjectService,
@@ -610,6 +625,7 @@ public TestEnvironment()
         }
 
         public ParatextController Controller { get; }
+        public IExceptionHandler ExceptionHandler { get; }
         public IMachineProjectService MachineProjectService { get; }
         public IParatextService ParatextService { get; }
         public ISFProjectService ProjectService { get; }