fix: preserve blank CVs and reliable editor undo

JobTrackerApi.Tests/CvExportRevisionTests.cs

@@ -16,6 +16,27 @@ namespace JobTrackerApi.Tests;
 
 public sealed class CvExportRevisionTests
 {
+    [Fact]
+    public async Task Explicit_blank_export_is_rejected_before_pdf_allocation()
+    {
+        var current = new Mock<ICurrentUserService>();
+        current.SetupGet(x => x.UserId).Returns("owner");
+        await using var db = new JobTrackerContext(new DbContextOptionsBuilder<JobTrackerContext>()
+            .UseInMemoryDatabase(Guid.NewGuid().ToString()).Options, current.Object);
+        var variants = new CvVariantService(db, new CareerProfileService(db), new ThemedCvRenderer());
+        var settings = CvVariantSettingsJson.Deserialize("{\"sectionsExplicit\":true,\"includeProfileContact\":false,\"sections\":[]}");
+        var cv = await variants.CreateAsync("owner", "Blank", null, settings, default);
+        var user = new ApplicationUser { Id = "owner", FirstName = "Inherited name" };
+        var users = TestHostFactory.CreateUserManager(user);
+        users.Setup(x => x.GetUserAsync(It.IsAny<ClaimsPrincipal>())).ReturnsAsync(user);
+        var pdf = new Mock<ICvPdfExporter>(MockBehavior.Strict);
+        var controller = new CvVariantController(users.Object, variants, pdf.Object, Mock.Of<ISummarizerService>())
+        { ControllerContext = new() { HttpContext = new DefaultHttpContext() } };
+        var result = Assert.IsType<BadRequestObjectResult>(await controller.ExportPdf(cv.Id, default, 1));
+        Assert.Equal("cv_empty_content", JsonSerializer.SerializeToElement(result.Value).GetProperty("code").GetString());
+        pdf.VerifyNoOtherCalls();
+    }
+
     [Theory]
     [InlineData(1, "owner", 409)]
     [InlineData(0, "owner", 409)]