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Slide deck generation fails with TypeError when the model omits "content"; slides always in English

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
92/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
php
Domain
backend

Research direction

Start in lib/Service/SlideDeckService.php, reading PROMPT and parseModelJSON() around line 142. Check the handling of missing title, subtitle, and content fields, then verify that malformed model output no longer causes a TypeError and that the prompt requests the presentation’s language for all slide text.

Written by the indexing model from the issue text.

Description

Version: richdocuments 12.0.0 · Nextcloud 35

Actual (log):
TitleContentSlide::__construct(): Argument #3 ($content) must be of type array|string, null given, called in lib/Service/SlideDeckService.php on line 142

Cause

  1. parseModelJSON() passes $slideJSON['content'] without checking it exists. Small local models sometimes return a layout: 1 slide with
    subtitle instead of content (observed with a ~4B model; a larger model returned valid JSON for the same prompt) → the whole task fails.
  2. SlideDeckService::PROMPT has no instruction about output language (the text/spreadsheet prompts do: "in the same language as the description"),
    so slides come out in English for non-English requests (observed for Thai with both a small and a large model).

Fix (tested): null-coalesce title/subtitle/content (fall back to subtitle for content), and add
"Write all slide texts in the same language as the presentation text." to the prompt. Patch below.

Patch (tested on a test instance):

--- a/lib/Service/SlideDeckService.php
+++ b/lib/Service/SlideDeckService.php
@@ -64,6 +64,8 @@
 
 Only output the JSON array. Do not wrap it with spaces, new lines or backticks (`).
 
+Write all slide texts in the same language as the presentation text.
+
 Here is the presentation text:
 EOF;
 
@@ -137,9 +139,9 @@
 			$slideLayout = LayoutType::from($layoutTypes[$slideJSON['layout']]);
 
 			$slide = match ($slideLayout) {
-				LayoutType::Title => new TitleSlide($index, $slideJSON['title'], $slideJSON['subtitle']),
+				LayoutType::Title => new TitleSlide($index, $slideJSON['title'] ?? '', $slideJSON['subtitle'] ?? ''),
 
-				LayoutType::TitleContent => new TitleContentSlide($index, $slideJSON['title'], $slideJSON['content']),
+				LayoutType::TitleContent => new TitleContentSlide($index, $slideJSON['title'] ?? '', $slideJSON['content'] ?? $slideJSON['subtitle'] ?? ''),
 
 				default => null,
 			};
Dominant language
JavaScript
Stars
453
Forks
147
Avg merge
18h 31m
Merged PRs (30d)
86

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