LV2 hosting: search paths are not scanned recursively

dave96 · September 8, 2026, 11:43am

Apologies for the cross post, I’m still not sure what the “correct” bug reporting platform is for JUCE?

[Bug]: LV2 hosting: search paths are not scanned recursively

opened 11:42AM - 08 Sep 26 UTC

### Detailed steps on how to reproduce the bug Tested against `develop` at 7278…2788 (JUCE 9.0.2). Any LV2 host built with `PluginListComponent` (e.g. AudioPluginHost) reproduces it. 1. Install an LV2 bundle at `~/.lv2/<name>.lv2` and scan for LV2 plugins. The plugin is found. 2. Move it to `~/.lv2/<name>/<name>.lv2` and rescan. The plugin is not found. 3. In the "Select folders to scan..." dialog, add `~/.lv2/<name>` as an extra search path (at any position in the list) and rescan. The plugin is still not found. The same folder layout works for VST3 and LADSPA. Cause 1: `LV2PluginFormatHeadless::Pimpl::searchPathsForPlugins (const FileSearchPath&, bool, bool)` in `juce_audio_processors_headless/format_types/juce_LV2PluginFormatImpl.h` ignores its `recursive` argument. It joins the paths into an `LV2_PATH` string and calls `lilv_world_load_all()`, and lilv (`load_dir_entry` in `LV2_SDK/lilv/src/world.c`) only checks the immediate children of each search directory for a `manifest.ttl`, so bundles in subfolders are never visited. VST3 and LADSPA use `File::findChildFiles (…, recursive)` and do descend. Cause 2: `PluginDirectoryScanner`'s constructor calls `directoriesToSearch.removeRedundantPaths()` before calling the format. The default LV2 path list contains `~/.lv2`, which `File` expands to the home directory, so `/home/<user>/.lv2/dRowAudio` is treated as a redundant child of it and silently dropped, whatever its position in the list. The scanner assumes recursion that the LV2 format never performs, so the explicit path is lost before the format sees it. ### What is the expected behaviour? LV2 bundles in subfolders of a search path should be found when `recursive` is true, matching VST3 and LADSPA, and an explicitly added sub-path should at minimum be honoured. Suggested fix: honour `recursive` in `searchPathsForPlugins()` by walking each search path with `File::findChildFiles (File::findDirectories, recursive)` and calling `lilv_world_load_bundle()` for every directory containing a `manifest.ttl` (as `findAllTypesForFile()` already does for an absolute path). That fixes both symptoms without changing `removeRedundantPaths()`. ### Operating systems Linux ### What versions of the operating systems? Ubuntu 24.04 ### Architectures Arm64/aarch64, x86_64 ### Stacktrace ```shell ``` ### Plug-in formats (if applicable) LV2 ### Plug-in host applications (DAWs) (if applicable) Waveform 14 ### Testing on the `develop` branch The bug is present on the `develop` branch ### Code of Conduct - [x] I agree to follow the Code of Conduct

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LV2 hosting: search paths are not scanned recursively

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