Fix IndexError when editing legacy webapps missing browser metadata

Commit 247f167 added browser restoration during edit but assumed
X-WebApp-Browser always exists. Legacy desktop files miss that key, so
on_edit_button hits IndexError at line 366, the GTK main loop stalls,
and CPU usage spikes.

Match by Exec when the name lookup fails, and fall back if nothing fits.
Editing now completes and rewrites the desktop file with fresh metadata.

Fix #345

Author: PeterDaveHello

usr/lib/webapp-manager/webapp-manager.py

@@ -4,6 +4,7 @@
 import gettext
 import locale
 import os
+import shlex
 import shutil
 import subprocess
 import warnings
@@ -23,6 +24,107 @@
 #   3. Local application/library specific imports.
 from common import _async, idle, WebAppManager, download_favicon, ICONS_DIR, BROWSER_TYPE_FIREFOX, BROWSER_TYPE_FIREFOX_FLATPAK, BROWSER_TYPE_ZEN_FLATPAK, BROWSER_TYPE_FIREFOX_SNAP
 
+
+def _strip_leading_env(tokens):
+    """Remove leading env invocations and KEY=VALUE assignments."""
+
+    def _consume_env_opts(index):
+        while index < len(tokens) and tokens[index].startswith("-"):
+            option = tokens[index]
+            index += 1
+            if option == "--":
+                return index
+            if option.startswith("-u") and option not in ("-u", "--unset"):
+                continue
+            if option.startswith("-C") and option not in ("-C", "--chdir"):
+                continue
+            if option.startswith("-S") and option not in ("-S", "--split-string"):
+                try:
+                    extra = shlex.split(option[2:])
+                except ValueError:
+                    extra = []
+                if extra:
+                    tokens[index:index] = extra
+                continue
+            if option in ("-u", "--unset", "-C", "--chdir", "-S", "--split-string") and index < len(tokens):
+                if option in ("-S", "--split-string"):
+                    try:
+                        extra = shlex.split(tokens[index])
+                    except ValueError:
+                        extra = []
+                    index += 1
+                    if extra:
+                        tokens[index:index] = extra
+                else:
+                    index += 1
+            elif option.startswith("--unset="):
+                continue
+            elif option.startswith("--chdir="):
+                continue
+            elif option.startswith("--split-string="):
+                try:
+                    extra = shlex.split(option.split("=", 1)[1])
+                except ValueError:
+                    extra = []
+                if extra:
+                    tokens[index:index] = extra
+                continue
+        while index < len(tokens) and "=" in tokens[index] and not tokens[index].startswith("-"):
+            index += 1
+        return index
+
+    idx = 0
+    while idx < len(tokens):
+        token = tokens[idx]
+        if token == "env" or os.path.basename(token) == "env":
+            idx = _consume_env_opts(idx + 1)
+            continue
+        if token == "--":
+            idx += 1
+            continue
+        if "=" in token and not token.startswith("--") and not token.startswith("-"):
+            idx += 1
+            continue
+        break
+    return tokens[idx:]
+
+
+def _extract_exec_binary(exec_line):
+    """Return the executable invoked by a desktop Exec line."""
+    if not exec_line:
+        return None
+    try:
+        tokens = shlex.split(exec_line)
+    except ValueError:
+        return None
+    if not tokens:
+        return None
+    tokens = _strip_leading_env(tokens)
+    if not tokens:
+        return None
+    if len(tokens) >= 3 and tokens[1] == "-c" and os.path.basename(tokens[0]) == "sh":
+        try:
+            inner_tokens = shlex.split(tokens[2])
+        except ValueError:
+            return None
+        inner_tokens = _strip_leading_env(inner_tokens)
+        if not inner_tokens:
+            return None
+        return inner_tokens[0]
+    return tokens[0]
+
+
+def _exec_matches(browser_exec_path, exec_binary):
+    if not exec_binary:
+        return False
+    if browser_exec_path == exec_binary:
+        return True
+    if os.path.isabs(browser_exec_path) and os.path.basename(browser_exec_path) == exec_binary:
+        return True
+    if os.path.isabs(exec_binary) and os.path.basename(exec_binary) == browser_exec_path:
+        return True
+    return False
+
 setproctitle.setproctitle("webapp-manager")
 
 # i18n
@@ -362,9 +464,18 @@ def on_edit_button(self, widget):
             self.isolated_switch.set_active(self.selected_webapp.isolate_profile)
             self.privatewindow_switch.set_active(self.selected_webapp.privatewindow)
 
-            web_browsers = map(lambda i: i[0], self.browser_combo.get_model())
-            selected_browser_index = [idx for idx, x in enumerate(web_browsers) if x.name == self.selected_webapp.web_browser][0]
-            self.browser_combo.set_active(selected_browser_index)
+            web_browsers = list(map(lambda i: i[0], self.browser_combo.get_model()))
+            matching_indexes = [idx for idx, x in enumerate(web_browsers)
+                                if x.name == self.selected_webapp.web_browser]
+            if not matching_indexes and self.selected_webapp.exec:
+                exec_binary = _extract_exec_binary(self.selected_webapp.exec)
+                if exec_binary:
+                    matching_indexes = [idx for idx, x in enumerate(web_browsers)
+                                        if _exec_matches(x.exec_path, exec_binary)]
+            if matching_indexes:
+                self.browser_combo.set_active(matching_indexes[0])
+            elif web_browsers:
+                self.browser_combo.set_active(0)
             self.on_browser_changed(self.selected_webapp)
 
             model = self.category_combo.get_model()