bug: Slides break when slide count changes with frozen slides

[shibayu36]

Version

1.22.1

What happened?

When a slide with freeze: true exists and the total number of slides changes (by inserting or deleting slides), the frozen slide disappears or wrong slides are preserved.

Reproduction (Insert case)

1. Create initial slides: Slide 1, Slide 2
2. Apply markdown inserting a slide before frozen slide:
   • Slide 1, Slide NEW, Slide 2 (freeze: true)
3. Expected: Slide 1, Slide NEW, Slide 2 (3 slides)
4. Actual: Slide 1, Slide NEW (2 slides - frozen Slide 2 disappears)

Reproduction (Delete case)

1. Create initial slides: Slide 1, Slide 2, Slide 3
2. Apply markdown deleting a slide before frozen slide:
   • Slide 1, Slide 3 (freeze: true)
3. Expected: Slide 1, Slide 3
4. Actual: Slide 1, Slide 2 (wrong slide preserved, frozen Slide 3 disappears)

error.json

[shibayu36]

Here are failing test cases that reproduce this bug:

diff --git a/action_test.go b/action_test.go
index 3a1f62e..d2aa3e9 100644
--- a/action_test.go
+++ b/action_test.go
@@ -1699,6 +1699,101 @@ var tests = []struct {
                      },
              },
      },
+     {
+             name: "freeze slide with insert before frozen slide",
+             before: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 2"},
+                             TitleBodies: toBodies([]string{"Slide 2"}),
+                     },
+             },
+             after: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide NEW"},
+                             TitleBodies: toBodies([]string{"Slide NEW"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 2"},
+                             TitleBodies: toBodies([]string{"Slide 2"}),
+                             Freeze:      true,
+                     },
+             },
+             want: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide NEW"},
+                             TitleBodies: toBodies([]string{"Slide NEW"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 2"},
+                             TitleBodies: toBodies([]string{"Slide 2"}),
+                     },
+             },
+     },
+     {
+             name: "freeze slide with delete before frozen slide",
+             before: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 2"},
+                             TitleBodies: toBodies([]string{"Slide 2"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 3"},
+                             TitleBodies: toBodies([]string{"Slide 3"}),
+                     },
+             },
+             after: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 3"},
+                             TitleBodies: toBodies([]string{"Slide 3"}),
+                             Freeze:      true,
+                     },
+             },
+             want: Slides{
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 1"},
+                             TitleBodies: toBodies([]string{"Slide 1"}),
+                     },
+                     {
+                             Layout:      "title",
+                             Titles:      []string{"Slide 3"},
+                             TitleBodies: toBodies([]string{"Slide 3"}),
+                     },
+             },
+     },

[k1LoW]

@shibayu36 Thank you for your report!! I'll check it.

[k1LoW]

This appears to be a difference in implementation between: "1. Determine which index to freeze before performing the slide operation" versus "2. Perform the slide operation first, then determine which page to freeze."
Currently, we are implementing it under option 1.

However, a more intuitive implementation might be the second one.

umm...

(It should be noted that in both implementations, there is a possibility that users might mistakenly freeze the wrong objects.)