[PATCH 4/9] lib: Make notmuch_database_get_directory return NULL if the directory is not found

[Austin Clements]

Using the new support from _notmuch_directory_create, this makes
notmuch_database_get_directory a read-only operation that simply
returns the directory object if it exists or NULL otherwise.  This
also means that notmuch_database_get_directory can work on read-only
databases.

This change breaks the directory mtime workaround in notmuch-new.c by
fixing the exact issue it was working around.  This permits mtime
update races to prevent scans of changed directories, which
non-deterministically breaks a few tests.  The next patch fixes this.
---
 lib/database.cc       |    7 ++-----
 lib/notmuch-private.h |    3 +++
 lib/notmuch.h         |   10 ++--------
 3 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/lib/database.cc b/lib/database.cc
index b4c76b4..e27a0e1 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -1328,12 +1328,9 @@ notmuch_database_get_directory (notmuch_database_t *notmuch,
 	return NOTMUCH_STATUS_NULL_POINTER;
     *directory = NULL;
 
-    /* XXX Handle read-only databases properly */
-    if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY)
-	return NOTMUCH_STATUS_READ_ONLY_DATABASE;
-
     try {
-	*directory = _notmuch_directory_create (notmuch, path, NOTMUCH_FIND_CREATE, &status);
+	*directory = _notmuch_directory_create (notmuch, path,
+						NOTMUCH_FIND_LOOKUP, &status);
     } catch (const Xapian::Error &error) {
 	fprintf (stderr, "A Xapian exception occurred getting directory: %s.\n",
 		 error.get_msg().c_str());
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 34f7ac7..bfb4111 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -148,6 +148,9 @@ typedef enum _notmuch_private_status {
 
 /* Flags shared by various lookup functions. */
 typedef enum _notmuch_find_flags {
+    /* Lookup without creating any documents.  This is the default
+     * behavior. */
+    NOTMUCH_FIND_LOOKUP = 0,
     /* If set, create the necessary document (or documents) if they
      * are missing.  Requires a read/write database. */
     NOTMUCH_FIND_CREATE = 1<<0,
diff --git a/lib/notmuch.h b/lib/notmuch.h
index bbb17e4..3633bed 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -300,10 +300,8 @@ notmuch_database_end_atomic (notmuch_database_t *notmuch);
  * (see notmuch_database_get_path), or else should be an absolute path
  * with initial components that match the path of 'database'.
  *
- * Note: Currently this will create the directory object if it doesn't
- * exist.  In the future, when a directory object does not exist this
- * will return NOTMUCH_STATUS_SUCCESS and set *directory to NULL.
- * Callers should be prepared for this.
+ * If this directory object does not exist in the database, this
+ * returns NOTMUCH_STATUS_SUCCESS and sets *directory to NULL.
  *
  * Return value:
  *
@@ -313,10 +311,6 @@ notmuch_database_end_atomic (notmuch_database_t *notmuch);
  *
  * NOTMUCH_STATUS_XAPIAN_EXCEPTION: A Xapian exception occurred;
  *	directory not retrieved.
- *
- * NOTMUCH_STATUS_READ_ONLY_DATABASE: Database was opened in read-only
- *	mode so the directory cannot be created (this case will be
- *	removed in the future).
  */
 notmuch_status_t
 notmuch_database_get_directory (notmuch_database_t *database,
-- 
1.7.10