Split command-line-generating code into its own function

packaging_scripts/repos.py

@@ -7,7 +7,6 @@ import subprocess
 # ========== Constants ==========
 REPO_ADD_CMD = '/usr/bin/repo-add'
 REPO_REMOVE_CMD = '/usr/bin/repo-remove'
-DB_EXT = 'db.tar.xz'
 
 # ========== Logging setup ==========
 syslog = logging.getLogger(__name__)
@@ -19,6 +18,41 @@ class RepoAddError(BaseException):
 
 
 # ========== Functions ==========
+def gen_cmdline(operation, db, opts, *pkgs):
+    """Generate a command suitable for invoking either repo-add or
+    repo-remove.
+
+    :param operation: run either repo-add or repo-remove
+    :type operation: str
+    :param db: the database file to operate on
+    :type db: str, bytes, or path-like object
+    :param opts: extra options to pass to repo-add
+    :type opts: list
+    :param pkgs: these arguments depend on whether the operation is
+        an add or remove.
+        If operation is 'add', then pkgs is all of the paths of the
+        package files to add to the database. If operation is 'remove',
+        then pkgs is the name of the packages to remove from the database.
+    :type pkgs: any iterable
+    :returns: list of command-line arguments suitable for passing to
+        subprocess.run()
+    :rtype: list
+    :raises: ValueError if operation was invalid
+    """
+    if not operation == 'add' or operation == 'remove':
+        raise ValueError('Invalid operation was raised')
+
+    cmd = [f"/usr/bin/repo-{operation}"]
+
+    if opts is not None:
+        cmd.extend(opts)
+
+    cmd.append(db)
+    cmd.extend(pkgs)
+
+    return cmd
+
+
 def repo_add(operation, db, *pkgs, opts=None):
     """Run repo-add.
 
@@ -43,29 +77,21 @@ def repo_add(operation, db, *pkgs, opts=None):
     """
     if operation == 'add':
         syslog.info('Adding packages to database')
-        cmd = [REPO_ADD_CMD]
     else:
         syslog.info('Removing packages from database')
-        cmd = [REPO_REMOVE_CMD]
 
     syslog.debug(f"Database: {db}")
     syslog.debug(f"Options: {opts}")
     syslog.debug(f"Packages: {pkgs}")
 
-    if opts is not None:
-        cmd.extend(opts)
-
-    cmd.append(db)
-    cmd.extend(pkgs)
-    syslog.debug(f"Final repo-add command: {cmd}")
-
     try:
+        cmd = gen_cmdline(operation, db, opts, *pkgs)
         process = subprocess.run(cmd,
                                  check=True,
                                  capture_output=True,
                                  text=True)
-    except RepoAddError:
+    except subprocess.CalledProcessError:
         raise RepoAddError(process.stderr)
     else:
         syslog.debug(process.stdout)
-        syslog.info('Finished adding packages to database')
+        syslog.info('Database operation complete')