cli: use designated initializers for opt desc

Several changes at once, just to not have to change the same lines
several times over:

- Use designated initializers to initialize opt desc arrays.

- Only initialize the needed fields.

- Remove arg_id (short options) as unused.

- Replace opt_type and output_var with several type safe output
  variables, where the output variable being non-NULL determines the
  type. Introduce checks to ensure only one is set. The downside is
  some waste of const space per argument; this could be saved by
  retaining opt_type and using a union, but that's still pretty
  verbose.

- Fix some variables due to the type safety. Mostly a good thing, but
  leads to some enums being changed to ints. This is pedantically
  correct, but somewhat annoying. We could also cast, but that defeats
  the purpose a bit.

- Terminate the opt desc arrays using {}.

The output variable type safety and the ability to add new fields for
just some output types or arguments are the big wins. For example, if
we wanted to add a variable to set when the argument is present, we
could do so for just the arguments that need it.

Beauty is in the eye of the beholder, but I think this looks nice when
defining the arguments, and reduces some of the verbosity we have
there.

1 files changed, 13 insertions, 25 deletions

diff --git a/command-line-arguments.h b/command-line-arguments.h
index 4c4d240e..ff51abce 100644
--- a/command-line-arguments.h
+++ b/command-line-arguments.h
@@ -3,17 +3,6 @@
 
 #include "notmuch.h"
 
-enum notmuch_opt_type {
-    NOTMUCH_OPT_END = 0,
-    NOTMUCH_OPT_INHERIT,	/* another options table */
-    NOTMUCH_OPT_BOOLEAN,	/* --verbose              */
-    NOTMUCH_OPT_INT,		/* --frob=8               */
-    NOTMUCH_OPT_KEYWORD,	/* --format=raw|json|text */
-    NOTMUCH_OPT_KEYWORD_FLAGS,	/* the above with values OR'd together */
-    NOTMUCH_OPT_STRING,		/* --file=/tmp/gnarf.txt  */
-    NOTMUCH_OPT_POSITION	/* notmuch dump pos_arg   */
-};
-
 /*
  * Describe one of the possibilities for a keyword option
  * 'value' will be copied to the output variable
@@ -24,22 +13,21 @@ typedef struct notmuch_keyword {
     int value;
 } notmuch_keyword_t;
 
-/*
- * Describe one option.
- *
- * First two parameters are mandatory.
- *
- * name is mandatory _except_ for positional arguments.
- *
- * arg_id is currently unused, but could define short arguments.
- *
- * keywords is a (possibly NULL) pointer to an array of keywords
- */
+/* Describe one option. */
 typedef struct notmuch_opt_desc {
-    enum notmuch_opt_type opt_type;
-    void *output_var;
+    /* One and only one of opt_* must be set. */
+    const struct notmuch_opt_desc *opt_inherit;
+    notmuch_bool_t *opt_bool;
+    int *opt_int;
+    int *opt_keyword;
+    int *opt_flags;
+    const char **opt_string;
+    const char **opt_position;
+
+    /* Must be set except for opt_inherit and opt_position. */
     const char *name;
-    int  arg_id;
+
+    /* Must be set for opt_keyword and opt_flags. */
     const struct notmuch_keyword *keywords;
 } notmuch_opt_desc_t;