Open picked files through the content resolver, not std::fs

Loading a GPX on Android failed for every file in the picker. The dialog
plugin fires ACTION_GET_CONTENT, which returns a `content://` URI, and
`load_profile_from_path` handed that straight to `std::fs::read_to_string`
— "no such file or directory" for a file the rider is looking at. Picking
from Nextcloud makes it plainer: a document provider backed by a server
may have no local file at all until the resolver opens the stream, so
there was never a path to find.

So the command now takes a `FilePath` and reads through tauri-plugin-fs,
which opens a path directly and a URI via the resolver. The plugin is
here for `FsExt` alone; nothing in ui/ calls its commands, so the
capabilities are unchanged.

Two things that were derived from the filename can no longer be:

  - GPX is detected by content. A document id need not contain a name,
    let alone an extension. No YAML profile begins with `<`.
  - The route name falls back to the GPX's own <name>. Providers over
    real storage encode the filename in the last segment, but an opaque
    row id would have made a wretched route name.

save_fit had the same bug on the export side — PathBuf::from on a
save-dialog URI — and now writes down a resolver descriptor when handed
one.

Note for anyone rebuilding locally: gen/android/tauri.settings.gradle is
autogenerated and lists each plugin's Android project, so the new
plugin's Kotlin only reaches the APK after `cargo tauri android init` and
scripts/sync-android-sources.sh. CI already runs both.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -255,6 +255,7 @@ dependencies = [
  "tauri",
  "tauri-build",
  "tauri-plugin-dialog",
+ "tauri-plugin-fs",
  "thiserror 2.0.19",
  "tokio",
  "tracing",

src-tauri/Cargo.toml

@@ -22,6 +22,11 @@ bikecontrol-fit = { workspace = true }
 
 tauri = { version = "2", features = [] }
 tauri-plugin-dialog = "2"
+# Not for the frontend — nothing in `ui/` calls the fs commands. This is here
+# for `FsExt::read_to_string`, the one API that can read what the *picker*
+# returns on Android: a `content://` URI rather than a path. See
+# `read_picked_file` in commands.rs.
+tauri-plugin-fs = "2"
 
 uuid = { workspace = true }
 chrono = { workspace = true }

src-tauri/src/commands.rs

@@ -4,12 +4,13 @@
 //! they mutate Rust-side state and the resulting truth comes back on the event
 //! channel. The UI never assumes a command took effect (§4.3).
 
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 use bikecontrol_core::gpx::{self, SmoothingConfig};
 use bikecontrol_core::profile::Profile;
 use bikecontrol_core::types::{ControlMode, RiderConfig, SafetyLimits};
 use tauri::{AppHandle, State};
+use tauri_plugin_fs::{FilePath, FsExt, OpenOptions};
 
 use bikecontrol_ble::PodId;
 
@@ -188,8 +189,7 @@ pub fn ride_summary(state: State<'_, AppState>) -> Option<RideSummary> {
 /// Returns the path actually written, so the UI can confirm it rather than
 /// claiming success against a path it merely proposed.
 #[tauri::command]
-pub fn save_fit(app: AppHandle, state: State<'_, AppState>, path: String) -> Cmd<String> {
+pub fn save_fit(app: AppHandle, state: State<'_, AppState>, path: FilePath) -> Cmd<String> {
-    let dest = PathBuf::from(&path);
     let source = {
         let inner = state.lock();
         let summary = inner
@@ -199,8 +199,15 @@ pub fn save_fit(app: AppHandle, state: State<'_, AppState>, path: String) -> Cmd
         PathBuf::from(&summary.fit_path)
     };
 
-    recording::save_copy(&source, &dest)?;
+    match &path {
-    let written = dest.display().to_string();
+        FilePath::Path(dest) => recording::save_copy(&source, dest)?,
+        // Android: the save dialog returns a `content://` URI for a document
+        // the provider has already created. There is no directory to make and
+        // no path to copy to — the bytes go down a descriptor the resolver
+        // opens, which is the same reason `read_picked_file` exists.
+        FilePath::Url(_) => write_through_resolver(&app, &path, &source)?,
+    }
+    let written = path.to_string();
     if let Some(summary) = state.lock().last_summary.as_mut() {
         summary.saved_path = Some(written.clone());
     }
@@ -209,6 +216,28 @@ pub fn save_fit(app: AppHandle, state: State<'_, AppState>, path: String) -> Cmd
     Ok(written)
 }
 
+/// Copy the activity into a document the rider chose from an Android picker.
+///
+/// The `std::fs` path in `recording::save_copy` cannot do this: there is no
+/// filesystem path on the other end, only a URI the content resolver can turn
+/// into a writable descriptor. Still a copy, never a move, for the reason
+/// `save_copy` documents — the automatic file in the rides directory has to
+/// survive a failed export.
+fn write_through_resolver(app: &AppHandle, dest: &FilePath, source: &Path) -> Result<(), String> {
+    let mut from = std::fs::File::open(source)
+        .map_err(|e| format!("{} is gone — nothing to save: {e}", source.display()))?;
+    let mut to = app
+        .fs()
+        .open(
+            dest.clone(),
+            OpenOptions::new().write(true).truncate(true).clone(),
+        )
+        .map_err(|e| format!("could not save to {dest}: {e}"))?;
+    std::io::copy(&mut from, &mut to)
+        .map(|_| ())
+        .map_err(|e| format!("could not save to {dest}: {e}"))
+}
+
 #[tauri::command]
 pub fn reset_ride(app: AppHandle, state: State<'_, AppState>) -> Cmd<RideState> {
     state.lock().reset_ride();
@@ -453,22 +482,101 @@ fn parse_profile(text: &str, name: &str, is_gpx: bool) -> Result<Profile, String
     }
 }
 
-/// Load a profile from a path on disk. GPX is detected by extension, everything
+/// Read a file the rider picked, wherever it actually lives.
-/// else is treated as the YAML profile format.
+///
+/// `std::fs` is not enough, and Android is why. The dialog plugin's picker
+/// fires `ACTION_GET_CONTENT`, which hands back a `content://` URI rather than
+/// a path; `std::fs::read_to_string` on one of those fails with "no such file
+/// or directory" — an error the rider gets for a file they are looking at in
+/// the picker. And for a provider backed by a server rather than storage
+/// (Nextcloud, Drive) there may be no local file at all until the resolver
+/// opens the stream, so no amount of path-guessing could have found one.
+///
+/// `tauri_plugin_fs` is the piece that knows the difference: a plain path is
+/// opened directly, a URI goes through the Android content resolver for a file
+/// descriptor. On desktop it is `std::fs` with extra steps.
+fn read_picked_file(app: &AppHandle, path: &FilePath) -> Result<String, String> {
+    app.fs()
+        .read_to_string(path.clone())
+        .map_err(|e| format!("{path}: {e}"))
+}
+
+/// Whether a picked file is GPX, decided by content rather than by name.
+///
+/// The extension is not always there to read: a `content://` URI carries a
+/// document id, which for some providers contains no filename at all. XML is
+/// unmistakable next to the YAML profile format — no YAML document begins with
+/// `<` — so the first non-space character is the reliable test and the
+/// extension is only a fast path.
+fn looks_like_gpx(path: &FilePath, text: &str) -> bool {
+    path.to_string().to_ascii_lowercase().ends_with(".gpx") || text.trim_start().starts_with('<')
+}
+
+/// The filename behind a picked file, if there is one to be had.
+///
+/// A `FilePath::Path` always has a stem. A URI might: providers over real
+/// storage encode the path in the last segment, percent-escaped but with the
+/// extension intact (`primary%3ADownload%2Fventoux.gpx`). Others use opaque row
+/// ids, which would make a terrible route name — so "does it end in an
+/// extension we know" is the test, and anything else gets `None` and falls back
+/// to the name inside the GPX.
+fn picked_file_stem(path: &FilePath) -> Option<String> {
+    match path {
+        FilePath::Path(p) => p.file_stem().map(|s| s.to_string_lossy().to_string()),
+        FilePath::Url(url) => {
+            let (stem, ext) = url.path_segments()?.next_back()?.rsplit_once('.')?;
+            if !matches!(ext.to_ascii_lowercase().as_str(), "gpx" | "yaml" | "yml") {
+                return None;
+            }
+            // The escaped separators are all that stands between the document
+            // id and the name inside it.
+            let decoded = stem
+                .replace("%2F", "/")
+                .replace("%2f", "/")
+                .replace("%3A", ":")
+                .replace("%3a", ":");
+            let name = decoded.rsplit(['/', ':']).next().unwrap_or(&decoded);
+            (!name.is_empty()).then(|| name.to_string())
+        }
+    }
+}
+
+/// The route's own name: `<metadata><name>`, else the first `<trk><name>`.
+///
+/// The fallback when the picker gave us no filename to use. Matches on local
+/// names so a namespaced document (`<g:trk>`) is not silently skipped, for the
+/// same reason `core::gpx` does.
+fn gpx_name(xml: &str) -> Option<String> {
+    let doc = roxmltree::Document::parse(xml).ok()?;
+    let named = |parent: &str| {
+        doc.descendants()
+            .find(|n| n.is_element() && n.tag_name().name() == parent)?
+            .children()
+            .find(|c| c.is_element() && c.tag_name().name() == "name")?
+            .text()
+            .map(str::trim)
+            .filter(|s| !s.is_empty())
+            .map(str::to_string)
+    };
+    named("metadata").or_else(|| named("trk"))
+}
+
+/// Load a profile the rider picked: a path on desktop, a `content://` URI on
+/// Android. GPX is detected by content, everything else is treated as the YAML
+/// profile format.
 #[tauri::command]
 pub fn load_profile_from_path(
     app: AppHandle,
     state: State<'_, AppState>,
-    path: String,
+    path: FilePath,
 ) -> Cmd<ProfileView> {
-    let text = std::fs::read_to_string(&path).map_err(|e| format!("{path}: {e}"))?;
+    let text = read_picked_file(&app, &path)?;
-    let stem = std::path::Path::new(&path)
+    let is_gpx = looks_like_gpx(&path, &text);
-        .file_stem()
+    let name = picked_file_stem(&path)
-        .map(|s| s.to_string_lossy().to_string())
+        .or_else(|| gpx_name(&text))
         .unwrap_or_else(|| "Profile".into());
-    let is_gpx = path.to_ascii_lowercase().ends_with(".gpx");
+    let profile = parse_profile(&text, &name, is_gpx)?;
-    let profile = parse_profile(&text, &stem, is_gpx)?;
+    let (view, geom) = profile_view::build(&profile, path.to_string());
-    let (view, geom) = profile_view::build(&profile, path);
     state.lock().set_profile(profile, view.clone(), geom);
     emit_ride_state(&app);
     notify(

src-tauri/src/lib.rs

@@ -66,6 +66,7 @@ pub fn run() {
 
     tauri::Builder::default()
         .plugin(tauri_plugin_dialog::init())
+        .plugin(tauri_plugin_fs::init())
         .manage(AppState::new())
         .invoke_handler(tauri::generate_handler![
             // ride lifecycle