Add argument to list packages needed by apps

doc/plinth.xml

@@ -48,6 +48,10 @@
         <option>--setup-no-repeat</option>
         <arg choice="opt" rep="repeat">application</arg>
       </arg>
+      <arg>
+        <option>--list-dependencies</option>
+        <arg choice="opt" rep="repeat">application</arg>
+      </arg>
     </cmdsynopsis>
   </refsynopsisdiv>
 
@@ -151,6 +155,24 @@
           </para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term><option>--list-dependencies</option></term>
+        <listitem>
+          <para>
+            For the list of provided applications, print the list of
+            packages needed by the applications.  If no application is
+            provided as additional argument, then print list of
+            packages needed by all essential applications.  If '*' is
+            provided in the list of the applications, then list of
+            packages needed by all applications will be printed.
+            Although, packages are installed when the application is
+            first accessed, this list will be useful for adding list
+            of dependencies to a Debian package and to get a list of
+            all interesting packages.  Other output may be printed on
+            stderr and should be ignored.
+          </para>
+        </listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 

plinth/__main__.py

@@ -60,6 +60,9 @@ def parse_arguments():
     parser.add_argument(
         '--diagnose', action='store_true', default=False,
         help='run diagnostic tests and exit')
+    parser.add_argument(
+        '--list-dependencies', default=False, nargs='*',
+        help='list package dependencies for essential modules')
 
     global arguments
     arguments = parser.parse_args()
@@ -267,6 +270,21 @@ def run_setup_and_exit(module_list, allow_install=True):
     sys.exit(error_code)
 
 
+def list_dependencies(module_list):
+    """List dependencies for all essential modules and exit."""
+    error_code = 0
+    try:
+        if module_list:
+            setup.list_dependencies(module_list=module_list)
+        else:
+            setup.list_dependencies(essential=True)
+    except Exception as exception:
+        logger.error('Error listing dependencies - %s', exception)
+        error_code = 1
+
+    sys.exit(error_code)
+
+
 def run_diagnostics_and_exit():
     """Run diagostics on all modules and exit."""
     module = importlib.import_module('plinth.modules.diagnostics.diagnostics')
@@ -309,6 +327,9 @@ def main():
     if arguments.setup_no_install is not False:
         run_setup_and_exit(arguments.setup_no_install, allow_install=False)
 
+    if arguments.list_dependencies is not False:
+        list_dependencies(arguments.list_dependencies)
+
     if arguments.diagnose:
         run_diagnostics_and_exit()
 

plinth/setup.py

@@ -175,3 +175,17 @@ def setup_modules(module_list=None, essential=False, allow_install=True):
             continue
 
         module.setup_helper.run(allow_install=allow_install)
+
+
+def list_dependencies(module_list=None, essential=False):
+    """Print list of packages required by selected or essential modules."""
+    for module_name, module in plinth.module_loader.loaded_modules.items():
+        if essential and not getattr(module, 'is_essential', False):
+            continue
+
+        if module_list and module_name not in module_list and \
+           '*' not in module_list:
+            continue
+
+        for package_name in getattr(module, 'managed_packages', []):
+            print(package_name)