Desktop: an AppImage beside the .deb, built and started in CI

.github/workflows/desktop.yml

@@ -1,6 +1,6 @@
 # Build the desktop app on every push, and attach it to every release.
 #
-# On a push, the Windows installer and the Linux .deb are built
+# On a push, the Windows installer and the Linux .deb and AppImage are built
 # and kept as workflow artifacts, so a change that breaks them shows up on the
 # commit that made it, and anyone can try that commit's build.
 #
@@ -244,9 +244,12 @@ jobs:
         working-directory: desktop
         run: npm ci
 
-      - name: Build the .deb
+      - name: Build the .deb and the AppImage
         working-directory: desktop
         env:
+          # linuxdeploy is itself an AppImage, and a runner has no FUSE.
+          APPIMAGE_EXTRACT_AND_RUN: '1'
+          NO_STRIP: 'true'
           MPFTP_EMU_RUNTIME: ${{ github.workspace }}/.workbench/assets/pydevices
         # The cargo cache restores target/, packages from earlier versions included.
         run: |
@@ -271,6 +274,14 @@ jobs:
           ls -l "$deb"
           sha256sum "$deb"
           echo "deb=$deb" >> "$GITHUB_OUTPUT"
+          appimages=("$bundle"/appimage/*.AppImage)
+          [[ ${#appimages[@]} -eq 1 ]] || { echo "::error::expected one AppImage, found ${#appimages[@]}"; exit 1; }
+          ls -l "${appimages[0]}"
+          sha256sum "${appimages[0]}"
+          echo "appimage=${appimages[0]}" >> "$GITHUB_OUTPUT"
+          # One folder, so the artifact holds both files at its top level.
+          mkdir linux-out
+          cp "$deb" "${appimages[0]}" linux-out/
 
       # Run what was built, as someone would: install the .deb, start the app
       # on a virtual display, and check that it started its Python host and
@@ -280,10 +291,15 @@ jobs:
           DEB: ${{ steps.built.outputs.deb }}
         run: bash desktop/scripts/smoke_linux.sh deb "$DEB"
 
+      - name: Run the AppImage
+        env:
+          APPIMAGE: ${{ steps.built.outputs.appimage }}
+        run: bash desktop/scripts/smoke_linux.sh appimage "$APPIMAGE"
+
       - uses: actions/upload-artifact@v7
         with:
           name: mpftp-desktop-linux-x64
-          path: ${{ steps.built.outputs.deb }}
+          path: linux-out/
           if-no-files-found: error
           compression-level: 0
 
@@ -322,8 +338,8 @@ jobs:
         run: |
           set -euo pipefail
           shopt -s nullglob
-          files=(dist/*-setup.exe dist/*.deb)
-          [[ ${#files[@]} -eq 2 ]] || { echo "::error::expected two installers, found ${#files[@]}"; ls -l dist; exit 1; }
+          files=(dist/*-setup.exe dist/*.deb dist/*.AppImage)
+          [[ ${#files[@]} -eq 3 ]] || { echo "::error::expected three installers, found ${#files[@]}"; ls -l dist; exit 1; }
           # Installers are named with the semver form: 0.1.5rc2 is 0.1.5-rc.2.
           semver="$(sed -E 's/^([0-9]+\.[0-9]+\.[0-9]+)(a|b|rc)([0-9]+)$/\1-\2.\3/; s/^([0-9]+\.[0-9]+\.[0-9]+)\.dev([0-9]+)$/\1-dev.\2/' <<< "$version")"
           for f in "${files[@]}"; do

ROADMAP.md

@@ -9,8 +9,6 @@ if something is broken or missing for you, open an
 - **One-click installers.** mpftp with its own Python inside. [Desktop](desktop/README.md)
   is a preview for Windows and Linux, attached to every release; next come
   signed installers and macOS.
-- **Desktop as an AppImage.** One Linux download that carries its own
-  libraries, for distributions the `.deb` doesn't cover.
 - **Desktop updates itself.** Today it links to the latest release; an
   updater would fetch and install a new version for you.
 - **Where a search result comes from, in the row.** Package search in the

desktop/README.md

@@ -25,6 +25,10 @@ installers next to the wheel and the VS Code extension:
   `sudo apt install ./mpftp_<version>_amd64.deb` and start `mpftp`. With
   arguments, such as `mpftp --help` or `mpftp ls -d /dev/ttyACM0`, the same
   command is the CLI, run with the Python the package carries.
+- **Other Linux distributions:** `mpftp_<version>_amd64.AppImage`, one file
+  that carries its own libraries. Make it executable (`chmod +x`) and run it;
+  with arguments it is the CLI, as with the `.deb`. If your system has no FUSE,
+  run it with `--appimage-extract-and-run`.
 
 To serial ports on Linux, your user needs to be in the `dialout` group (or
 `uucp` on some distributions).
@@ -106,10 +110,10 @@ Then, from `desktop/`:
 ```bash
 npm ci
 npm run stage:linux      # a python-build-standalone Python with mpftp, in python-linux/
-npm run build:linux      # the .deb
+npm run build:linux      # the .deb and the AppImage
 ```
 
-It lands in `src-tauri/target/release/bundle/deb/`.
+They land in `src-tauri/target/release/bundle/deb/` and `.../appimage/`.
 `tauri.linux.conf.json` swaps the Windows Python for the Linux one, and
 [`scripts/smoke_linux.sh`](scripts/smoke_linux.sh) starts a built package and checks that its Python
 host comes up.

desktop/scripts/smoke_linux.sh

@@ -73,7 +73,9 @@ for name in host sidecar; do
     || { echo "::error::the $name runs $exe, not the bundled $python"; fail=1; }
 done
 
-app_pid="$(pgrep -f -x "$app" || pgrep -n -f 'squashfs-root/usr/bin/mpftp|/usr/bin/mpftp' || true)"
+# The app is the host's parent. An AppImage's AppRun starts it as a bare
+# `mpftp`, so its command line doesn't name the path.
+app_pid="$(ps -o ppid= -p "${host%%$'\n'*}" 2>/dev/null | tr -d ' ' || true)"
 echo "app: ${app_pid:-not found}"
 [[ -n "$app_pid" ]] && kill ${app_pid}
 for _ in $(seq 15); do

desktop/src-tauri/src/main.rs

@@ -453,6 +453,9 @@ fn spawn_host(python: &Path, log: &Path) -> std::io::Result<(Child, ChildStdin,
     cmd.args(["-m", "mpftp.desktop_host"])
         // The host starts its sidecar with this same Python.
         .env("MPFTP_PYTHON", python)
+        // An AppImage's AppRun points these at its own usr/, which the bundled Python must not see.
+        .env_remove("PYTHONHOME")
+        .env_remove("PYTHONPATH")
         .env("PYTHONNOUSERSITE", "1")
         .env("PYTHONUNBUFFERED", "1")
         .env("PYTHONUTF8", "1")
@@ -615,6 +618,9 @@ fn run_cli_if_asked() {
         .args(&args)
         // The CLI starts its sidecar with this same Python.
         .env("MPFTP_PYTHON", &python)
+        // An AppImage's AppRun points these at its own usr/, which the bundled Python must not see.
+        .env_remove("PYTHONHOME")
+        .env_remove("PYTHONPATH")
         .env("PYTHONNOUSERSITE", "1")
         .exec();
     eprintln!("mpftp: could not run {}: {err}", python.display());

desktop/src-tauri/tauri.linux.conf.json

@@ -1,6 +1,6 @@
 {
   "bundle": {
-    "targets": ["deb"],
+    "targets": ["deb", "appimage"],
     "resources": {
       "../python-win/": null,
       "../python-linux/": "python/"