Add downloadIfMissing parameter to media GetFileStream APIs.

[hahn-kev]

Let callers opt out of implicit remote downloads so the media manager can preview only locally cached files, while entry-editor callers still auto-fetch by passing true explicitly from JS.

This is required for the picture UI to show a load button.

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

The media stream APIs now accept a downloadIfMissing flag. Backend retrieval returns NotFound for uncached files when disabled, while frontend callers explicitly choose whether missing media should be downloaded.

Media download control

Layer / File(s)	Summary
Backend media retrieval contract backend/FwLite/...	Backend APIs propagate downloadIfMissing; uncached files return NotFound when downloading is disabled.
JavaScript bridge propagation backend/FwLite/FwLiteShared/..., frontend/viewer/src/lib/dotnet-types/..., frontend/viewer/src/project/demo/...	Invokable services, generated interfaces, and the demo API accept and forward the new parameter.
Frontend request policies frontend/viewer/src/lib/components/..., frontend/viewer/src/lib/entry-editor/..., frontend/viewer/src/lib/media-manager/...	Picture and audio loading enable downloads, while media manager previews disable implicit downloads.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• sillsdev/languageforge-lexbox#2358: Introduced the media manager stream API extended by this change.
• sillsdev/languageforge-lexbox#2412: Added picture consumers that use the updated stream contract.

Suggested reviewers: rmunn

Poem

A rabbit hops through streams anew,
With download flags in every queue.
Cached files stay snug in their bed,
Missing ones say “NotFound” instead.
Pictures bloom and audio plays—
Carrots cheer these clearer days! 🐇

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding a downloadIfMissing parameter to GetFileStream APIs.
Description check	✅ Passed	The description is directly related to the changes and explains the new opt-out behavior and picture UI impact.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch t3code/media-service-conditional-download

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	Jul 20, 2026, 7:50 AM
e2e (Inspect)	✅ No changes detected	-	Jul 20, 2026, 7:57 AM

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs (1)

1960-1967: 🎯 Functional Correctness | 🟠 Major | 🏗️ Heavy lift

Honor the new downloadIfMissing contract.

The parameter is accepted but ignored, so downloadIfMissing=true still returns NotFound for uncached files. This conflicts with IMiniLcmReadApi and LcmMediaService, where true permits downloading missing media. Implement the download path for this backend, or explicitly make this implementation cache-only and prevent callers from relying on the default behavior.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs` around lines 1960
- 1967, The GetFileStream method ignores downloadIfMissing; implement its
true-path behavior to retrieve missing media consistently with IMiniLcmReadApi
and LcmMediaService, while retaining cached-file reads. If this backend cannot
download media, explicitly enforce cache-only semantics and ensure callers
cannot rely on the default true value.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs`:
- Around line 1960-1967: The GetFileStream method ignores downloadIfMissing;
implement its true-path behavior to retrieve missing media consistently with
IMiniLcmReadApi and LcmMediaService, while retaining cached-file reads. If this
backend cannot download media, explicitly enforce cache-only semantics and
ensure callers cannot rely on the default true value.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 96efefd3-e29c-4c84-89ab-e11cf4116202

📥 Commits

Reviewing files that changed from the base of the PR and between 31da37e and c3ce240.

📒 Files selected for processing (13)

• backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
• backend/FwLite/FwLiteShared/Services/MediaFilesServiceJsInvokable.cs
• backend/FwLite/FwLiteShared/Services/MiniLcmJsInvokable.cs
• backend/FwLite/LcmCrdt/CrdtMiniLcmApi.cs
• backend/FwLite/LcmCrdt/MediaServer/LcmMediaService.cs
• backend/FwLite/MiniLcm/IMiniLcmReadApi.cs
• frontend/viewer/src/lib/components/field-editors/audio-input.svelte
• frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/IMediaFilesServiceJsInvokable.ts
• frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/IMiniLcmJsInvokable.ts
• frontend/viewer/src/lib/entry-editor/field-editors/EditPictureDialog.svelte
• frontend/viewer/src/lib/entry-editor/field-editors/PictureImage.svelte
• frontend/viewer/src/lib/media-manager/MediaFileDetail.svelte
• frontend/viewer/src/project/demo/in-memory-demo-api.ts

[rmunn]

LGTM.