ref-filter: libify get_ref_atom_value()

Finish removing die() calls from ref-filter formatting logic,
so that it could be used by other commands.

Change the signature of get_ref_atom_value() and underlying functions
by adding return value and strbuf parameter for error message.
Return value equals 0 upon success and -1 upon failure.
Upon failure, error message is appended to the strbuf.

Signed-off-by: Olga Telezhnaia <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: telezhnaya

ref-filter.c

@@ -1427,28 +1427,30 @@ static const char *get_refname(struct used_atom *atom, struct ref_array_item *re
 	return show_ref(&atom->u.refname, ref->refname);
 }
 
-static void get_object(struct ref_array_item *ref, const struct object_id *oid,
-		       int deref, struct object **obj)
+static int get_object(struct ref_array_item *ref, const struct object_id *oid,
+		       int deref, struct object **obj, struct strbuf *err)
 {
 	int eaten;
+	int ret = 0;
 	unsigned long size;
 	void *buf = get_obj(oid, obj, &size, &eaten);
 	if (!buf)
-		die(_("missing object %s for %s"),
-		    oid_to_hex(oid), ref->refname);
-	if (!*obj)
-		die(_("parse_object_buffer failed on %s for %s"),
-		    oid_to_hex(oid), ref->refname);
-
-	grab_values(ref->value, deref, *obj, buf, size);
+		ret = strbuf_addf_ret(err, -1, _("missing object %s for %s"),
+				      oid_to_hex(oid), ref->refname);
+	else if (!*obj)
+		ret = strbuf_addf_ret(err, -1, _("parse_object_buffer failed on %s for %s"),
+				      oid_to_hex(oid), ref->refname);
+	else
+		grab_values(ref->value, deref, *obj, buf, size);
 	if (!eaten)
 		free(buf);
+	return ret;
 }
 
 /*
  * Parse the object referred by ref, and grab needed value.
  */
-static void populate_value(struct ref_array_item *ref)
+static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 {
 	struct object *obj;
 	int i;
@@ -1570,16 +1572,17 @@ static void populate_value(struct ref_array_item *ref)
 			break;
 	}
 	if (used_atom_cnt <= i)
-		return;
+		return 0;
 
-	get_object(ref, &ref->objectname, 0, &obj);
+	if (get_object(ref, &ref->objectname, 0, &obj, err))
+		return -1;
 
 	/*
 	 * If there is no atom that wants to know about tagged
 	 * object, we are done.
 	 */
 	if (!need_tagged || (obj->type != OBJ_TAG))
-		return;
+		return 0;
 
 	/*
 	 * If it is a tag object, see if we use a value that derefs
@@ -1593,20 +1596,23 @@ static void populate_value(struct ref_array_item *ref)
 	 * is not consistent with what deref_tag() does
 	 * which peels the onion to the core.
 	 */
-	get_object(ref, tagged, 1, &obj);
+	return get_object(ref, tagged, 1, &obj, err);
 }
 
 /*
  * Given a ref, return the value for the atom.  This lazily gets value
  * out of the object by calling populate value.
  */
-static void get_ref_atom_value(struct ref_array_item *ref, int atom, struct atom_value **v)
+static int get_ref_atom_value(struct ref_array_item *ref, int atom,
+			      struct atom_value **v, struct strbuf *err)
 {
 	if (!ref->value) {
-		populate_value(ref);
+		if (populate_value(ref, err))
+			return -1;
 		fill_missing_values(ref->value);
 	}
 	*v = &ref->value[atom];
+	return 0;
 }
 
 /*
@@ -2130,9 +2136,13 @@ static int cmp_ref_sorting(struct ref_sorting *s, struct ref_array_item *a, stru
 	int cmp;
 	cmp_type cmp_type = used_atom[s->atom].type;
 	int (*cmp_fn)(const char *, const char *);
+	struct strbuf err = STRBUF_INIT;
 
-	get_ref_atom_value(a, s->atom, &va);
-	get_ref_atom_value(b, s->atom, &vb);
+	if (get_ref_atom_value(a, s->atom, &va, &err))
+		die("%s", err.buf);
+	if (get_ref_atom_value(b, s->atom, &vb, &err))
+		die("%s", err.buf);
+	strbuf_release(&err);
 	cmp_fn = s->ignore_case ? strcasecmp : strcmp;
 	if (s->version)
 		cmp = versioncmp(va->s, vb->s);
@@ -2210,12 +2220,8 @@ int format_ref_array_item(struct ref_array_item *info,
 		if (cp < sp)
 			append_literal(cp, sp, &state);
 		pos = parse_ref_filter_atom(format, sp + 2, ep, error_buf);
-		if (pos < 0) {
-			pop_stack_element(&state.stack);
-			return -1;
-		}
-		get_ref_atom_value(info, pos, &atomv);
-		if (atomv->handler(atomv, &state, error_buf)) {
+		if (pos < 0 || get_ref_atom_value(info, pos, &atomv, error_buf) ||
+		    atomv->handler(atomv, &state, error_buf)) {
 			pop_stack_element(&state.stack);
 			return -1;
 		}