lib: Consolidate checks for read-only database.

Previously, many checks were deep in the library just before a cast
operation. These have now been replaced with internal errors and new
checks have instead been added at the beginning of all top-levelentry
points requiring a read-write database.

The new checks now also use a single function for checking and
printing the error message. This will give us a convenient location to
extend the check, (such as based on database version as well).

1 files changed, 48 insertions, 19 deletions

diff --git a/lib/message.cc b/lib/message.cc
index 0fc54668..ea9c8bd9 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -174,11 +174,6 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
     unsigned int doc_id;
     char *term;
 
-    if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY) {
-	*status_ret = NOTMUCH_PRIVATE_STATUS_READONLY_DATABASE;
-	return NULL;
-    }
-
     *status_ret = NOTMUCH_PRIVATE_STATUS_SUCCESS;
 
     message = notmuch_database_find_message (notmuch, message_id);
@@ -192,6 +187,9 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
 	return NULL;
     }
 
+    if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY)
+	INTERNAL_ERROR ("Failure to ensure database is writable.");
+
     db = static_cast<Xapian::WritableDatabase *> (notmuch->xapian_db);
     try {
 	doc.add_term (term);
@@ -706,7 +704,12 @@ _notmuch_message_remove_term (notmuch_message_t *message,
 notmuch_status_t
 notmuch_message_add_tag (notmuch_message_t *message, const char *tag)
 {
-    notmuch_private_status_t status;
+    notmuch_private_status_t private_status;
+    notmuch_status_t status;
+
+    status = _notmuch_database_ensure_writable (message->notmuch);
+    if (status)
+	return status;
 
     if (tag == NULL)
 	return NOTMUCH_STATUS_NULL_POINTER;
@@ -714,10 +717,10 @@ notmuch_message_add_tag (notmuch_message_t *message, const char *tag)
     if (strlen (tag) > NOTMUCH_TAG_MAX)
 	return NOTMUCH_STATUS_TAG_TOO_LONG;
 
-    status = _notmuch_message_add_term (message, "tag", tag);
-    if (status) {
+    private_status = _notmuch_message_add_term (message, "tag", tag);
+    if (private_status) {
 	INTERNAL_ERROR ("_notmuch_message_add_term return unexpected value: %d\n",
-			status);
+			private_status);
     }
 
     if (! message->frozen)
@@ -729,7 +732,12 @@ notmuch_message_add_tag (notmuch_message_t *message, const char *tag)
 notmuch_status_t
 notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
 {
-    notmuch_private_status_t status;
+    notmuch_private_status_t private_status;
+    notmuch_status_t status;
+
+    status = _notmuch_database_ensure_writable (message->notmuch);
+    if (status)
+	return status;
 
     if (tag == NULL)
 	return NOTMUCH_STATUS_NULL_POINTER;
@@ -737,10 +745,10 @@ notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
     if (strlen (tag) > NOTMUCH_TAG_MAX)
 	return NOTMUCH_STATUS_TAG_TOO_LONG;
 
-    status = _notmuch_message_remove_term (message, "tag", tag);
-    if (status) {
+    private_status = _notmuch_message_remove_term (message, "tag", tag);
+    if (private_status) {
 	INTERNAL_ERROR ("_notmuch_message_remove_term return unexpected value: %d\n",
-			status);
+			private_status);
     }
 
     if (! message->frozen)
@@ -749,39 +757,60 @@ notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
     return NOTMUCH_STATUS_SUCCESS;
 }
 
-void
+notmuch_status_t
 notmuch_message_remove_all_tags (notmuch_message_t *message)
 {
-    notmuch_private_status_t status;
+    notmuch_private_status_t private_status;
+    notmuch_status_t status;
     notmuch_tags_t *tags;
     const char *tag;
 
+    status = _notmuch_database_ensure_writable (message->notmuch);
+    if (status)
+	return status;
+
     for (tags = notmuch_message_get_tags (message);
 	 notmuch_tags_has_more (tags);
 	 notmuch_tags_advance (tags))
     {
 	tag = notmuch_tags_get (tags);
 
-	status = _notmuch_message_remove_term (message, "tag", tag);
-	if (status) {
+	private_status = _notmuch_message_remove_term (message, "tag", tag);
+	if (private_status) {
 	    INTERNAL_ERROR ("_notmuch_message_remove_term return unexpected value: %d\n",
-			    status);
+			    private_status);
 	}
     }
 
     if (! message->frozen)
 	_notmuch_message_sync (message);
+
+    return NOTMUCH_STATUS_SUCCESS;
 }
 
-void
+notmuch_status_t
 notmuch_message_freeze (notmuch_message_t *message)
 {
+    notmuch_status_t status;
+
+    status = _notmuch_database_ensure_writable (message->notmuch);
+    if (status)
+	return status;
+
     message->frozen++;
+
+    return NOTMUCH_STATUS_SUCCESS;
 }
 
 notmuch_status_t
 notmuch_message_thaw (notmuch_message_t *message)
 {
+    notmuch_status_t status;
+
+    status = _notmuch_database_ensure_writable (message->notmuch);
+    if (status)
+	return status;
+
     if (message->frozen > 0) {
 	message->frozen--;
 	if (message->frozen == 0)