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fix: preserve frozen slides when slide count changes #537

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Merged
k1LoW merged 1 commit into from
Jul 7, 2026
+505 −9
Merged

fix: preserve frozen slides when slide count changes #537

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29 changes: 22 additions & 7 deletions action.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,19 +53,34 @@ func generateActions(before, after Slides) (_ []*action, err error) {
beforeCopy := copySlides(before)
afterCopy := copySlides(after)

// Resolve which before slide each frozen after slide corresponds to, and
// substitute the counterpart's current content into after. The
// similarity-based pipeline below then sees the pair as identical and
// generates no update/delete actions for it, regardless of slide count
// changes (https://github.com/k1LoW/deck/issues/479).
frozenPairs := resolveFrozenSlides(beforeCopy, afterCopy)
for i, afterSlide := range afterCopy {
if !afterSlide.Freeze {
continue
}
if beforeIdx, ok := frozenPairs[i]; ok {
preserved := copySlide(beforeCopy[beforeIdx])
preserved.Freeze = true
afterCopy[i] = preserved
} else {
// A frozen slide without a counterpart is created from its
// markdown content. Freeze must be cleared because it would
// suppress content application on append.
afterSlide.Freeze = false
}
}

// Adjust slide count
adjustedBefore, adjustedAfter, err := adjustSlideCount(beforeCopy, afterCopy)
if err != nil {
return nil, fmt.Errorf("failed to adjust slide count: %w", err)
}

// Prevent actions from being generated from indexes that should be frozen.
for i, afterSlide := range adjustedAfter {
if afterSlide.Freeze {
adjustedBefore[i] = copySlide(afterSlide)
}
}

// Map slides algorithm
mapping, err := mapSlides(adjustedBefore, adjustedAfter)
if err != nil {
Expand Down
241 changes: 239 additions & 2 deletions action_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1659,8 +1659,8 @@ var tests = []struct {
},
{
Layout: "title",
Titles: []string{"Slide C"},
TitleBodies: toBodies([]string{"Slide C"}),
Titles: []string{"Slide B"},
TitleBodies: toBodies([]string{"Slide B"}),
},
},
},
Expand Down Expand Up @@ -1699,6 +1699,243 @@ 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"}),
},
},
},
{
// The actual content of the frozen slide has diverged from its
// markdown source (the typical reason for freezing). The diverged
// content must survive an insertion before the frozen slide.
name: "freeze diverged 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 edited manually"},
TitleBodies: toBodies([]string{"Slide 2 edited manually"}),
},
},
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 edited manually"},
TitleBodies: toBodies([]string{"Slide 2 edited manually"}),
},
},
},
{
name: "freeze all slides with insert between",
before: Slides{
{
Layout: "title",
Titles: []string{"Slide P"},
TitleBodies: toBodies([]string{"Slide P"}),
},
{
Layout: "title",
Titles: []string{"Slide Q"},
TitleBodies: toBodies([]string{"Slide Q"}),
},
},
after: Slides{
{
Layout: "title",
Titles: []string{"Slide P"},
TitleBodies: toBodies([]string{"Slide P"}),
Freeze: true,
},
{
Layout: "title",
Titles: []string{"Slide NEW"},
TitleBodies: toBodies([]string{"Slide NEW"}),
},
{
Layout: "title",
Titles: []string{"Slide Q"},
TitleBodies: toBodies([]string{"Slide Q"}),
Freeze: true,
},
},
want: Slides{
{
Layout: "title",
Titles: []string{"Slide P"},
TitleBodies: toBodies([]string{"Slide P"}),
},
{
Layout: "title",
Titles: []string{"Slide NEW"},
TitleBodies: toBodies([]string{"Slide NEW"}),
},
{
Layout: "title",
Titles: []string{"Slide Q"},
TitleBodies: toBodies([]string{"Slide Q"}),
},
},
},
{
// A frozen slide that has no counterpart in the presentation is
// created from its markdown content. Freezing protects it from the
// next apply onward.
name: "freeze new slide without counterpart",
before: Slides{
{
Layout: "title",
Titles: []string{"Slide 1"},
TitleBodies: toBodies([]string{"Slide 1"}),
},
},
after: Slides{
{
Layout: "title",
Titles: []string{"Slide 1"},
TitleBodies: toBodies([]string{"Slide 1"}),
},
{
Layout: "title",
Titles: []string{"Slide F"},
TitleBodies: toBodies([]string{"Slide F"}),
Freeze: true,
},
},
want: Slides{
{
Layout: "title",
Titles: []string{"Slide 1"},
TitleBodies: toBodies([]string{"Slide 1"}),
},
{
Layout: "title",
Titles: []string{"Slide F"},
TitleBodies: toBodies([]string{"Slide F"}),
},
},
},
}

func TestGenerateActions(t *testing.T) {
Expand Down
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