add command registration chaining

Adds the ability to chain registration structures.  Modules can define a
command with the 'chain' and 'num_chain' fields defined in their
registration table, and the register_commands() function will initialize
these commands.  If the registration record creates a new command, then
the chained commands are created under it; otherwise, they are created
in the same context as the other commands (i.e. the parent argument).

2 files changed, 37 insertions, 8 deletions

diff --git a/src/helper/command.c b/src/helper/command.c
index 9cc996c2..b81d2d19 100644
--- a/src/helper/command.c
+++ b/src/helper/command.c
@@ -331,18 +331,36 @@ struct command* register_command(struct command_context *context,
 int register_commands(struct command_context *cmd_ctx, struct command *parent,
 		const struct command_registration *cmds)
 {
+	int retval = ERROR_OK;
 	unsigned i;
-	for (i = 0; cmds[i].name; i++)
+	for (i = 0; cmds[i].name || cmds[i].chain; i++)
 	{
-		struct command *c = register_command(cmd_ctx, parent, cmds + i);
-		if (NULL != c)
-			continue;
+		const struct command_registration *cr = cmds + i;
 
+		struct command *c = NULL;
+		if (NULL != cr->name)
+		{
+			c = register_command(cmd_ctx, parent, cr);
+			if (NULL == c)
+			{
+				retval = ERROR_FAIL;
+				break;
+			}
+		}
+		if (NULL != cr->chain)
+		{
+			struct command *p = c ? : parent;
+			retval = register_commands(cmd_ctx, p, cr->chain);
+			if (ERROR_OK != retval)
+				break;
+		}
+	}
+	if (ERROR_OK != retval)
+	{
 		for (unsigned j = 0; j < i; j++)
 			unregister_command(cmd_ctx, parent, cmds[j].name);
-		return ERROR_FAIL;
 	}
-	return ERROR_OK;
+	return retval;
 }
 
 int unregister_all_commands(struct command_context *context,
diff --git a/src/helper/command.h b/src/helper/command.h
index 7baa92d5..6e3e93af 100644
--- a/src/helper/command.h
+++ b/src/helper/command.h
@@ -202,10 +202,18 @@ struct command_registration {
 	const char *help;
 	/// a string listing the options and arguments, required or optional
 	const char *usage;
+
+	/**
+	 * If non-NULL, the commands in @c chain will be registered in
+	 * the same context and scope of this registration record.
+	 * This allows modules to inherit lists commands from other
+	 * modules.
+	 */
+	const struct command_registration *chain;
 };
 
 /// Use this as the last entry in an array of command_registration records.
-#define COMMAND_REGISTRATION_DONE { .name = NULL }
+#define COMMAND_REGISTRATION_DONE { .name = NULL, .chain = NULL }
 
 /**
  * Register a command @c handler that can be called from scripts during
@@ -238,7 +246,10 @@ struct command* register_command(struct command_context *cmd_ctx,
 
 /**
  * Register one or more commands in the specified context, as children
- * of @c parent (or top-level commends, if NULL).
+ * of @c parent (or top-level commends, if NULL).  In a registration's
+ * record contains a non-NULL @c chain member and name is NULL, the
+ * commands on the chain will be registered in the same context.
+ * Otherwise, the chained commands are added as children of the command.
  *
  * @param cmd_ctx The command_context in which to register the command.
  * @param parent Register this command as a child of this, or NULL to