lib: support reopening databases for write access.

In the future Xapian will apparently support this more conveniently
for the cases other than READ_ONLY => READ_ONLY

Conceptually this function seems to fit better in lib/open.cc;
database.cc is still large enough that moving the function makes
sense.

lib/database.cc

@@ -517,29 +517,6 @@ notmuch_database_close (notmuch_database_t *notmuch)
     return status;
 }
 
-notmuch_status_t
-notmuch_database_reopen (notmuch_database_t *notmuch,
-			 unused(notmuch_database_mode_t mode))
-{
-    if (_notmuch_database_mode (notmuch) != NOTMUCH_DATABASE_MODE_READ_ONLY)
-	return NOTMUCH_STATUS_UNSUPPORTED_OPERATION;
-
-    try {
-	notmuch->xapian_db->reopen ();
-    } catch (const Xapian::Error &error) {
-	if (! notmuch->exception_reported) {
-	    _notmuch_database_log (notmuch, "Error: A Xapian exception reopening database: %s\n",
-				   error.get_msg ().c_str ());
-	    notmuch->exception_reported = true;
-	}
-	return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
-    }
-
-    notmuch->view++;
-
-    return NOTMUCH_STATUS_SUCCESS;
-}
-
 static int
 unlink_cb (const char *path,
 	   unused (const struct stat *sb),

lib/notmuch.h

@@ -882,6 +882,12 @@ notmuch_database_get_all_tags (notmuch_database_t *db);
 /**
  * Reopen an open notmuch database.
  *
+ * @param [in] db	open notmuch database
+ * @param [in] mode	mode (read only or read-write) for reopened database.
+ *
+ * @retval #NOTMUCH_STATUS_SUCCESS
+ * @retval #NOTMUCH_STATUS_ILLEGAL_ARGUMENT	The passed database was not open.
+ * @retval #NOTMUCH_STATUS_XAPIAN_EXCEPTION	A Xapian exception occured
  */
 notmuch_status_t
 notmuch_database_reopen (notmuch_database_t *db, notmuch_database_mode_t mode);

lib/open.cc

@@ -511,3 +511,49 @@ notmuch_database_create_with_config (const char *database_path,
 	talloc_free (notmuch);
     return status;
 }
+
+notmuch_status_t
+notmuch_database_reopen (notmuch_database_t *notmuch,
+			 notmuch_database_mode_t new_mode)
+{
+    notmuch_database_mode_t cur_mode = _notmuch_database_mode (notmuch);
+
+    if (notmuch->xapian_db == NULL) {
+	_notmuch_database_log (notmuch, "Cannot reopen closed or nonexistent database\n");
+	return NOTMUCH_STATUS_ILLEGAL_ARGUMENT;
+    }
+
+    try {
+	if (cur_mode == new_mode &&
+	    new_mode == NOTMUCH_DATABASE_MODE_READ_ONLY) {
+	    notmuch->xapian_db->reopen ();
+	} else {
+	    notmuch->xapian_db->close ();
+
+	    delete notmuch->xapian_db;
+	    notmuch->xapian_db = NULL;
+	    /* no need to free the same object twice */
+	    notmuch->writable_xapian_db = NULL;
+
+	    if (new_mode == NOTMUCH_DATABASE_MODE_READ_WRITE) {
+		notmuch->writable_xapian_db = new Xapian::WritableDatabase (notmuch->xapian_path,
+									    DB_ACTION);
+		notmuch->xapian_db = notmuch->writable_xapian_db;
+	    } else {
+		notmuch->xapian_db = new Xapian::Database (notmuch->xapian_path,
+							   DB_ACTION);
+	    }
+	}
+    } catch (const Xapian::Error &error) {
+	if (! notmuch->exception_reported) {
+	    _notmuch_database_log (notmuch, "Error: A Xapian exception reopening database: %s\n",
+				   error.get_msg ().c_str ());
+	    notmuch->exception_reported = true;
+	}
+	return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+    }
+
+    notmuch->view++;
+    notmuch->open = true;
+    return NOTMUCH_STATUS_SUCCESS;
+}

test/T595-reopen.sh

@@ -0,0 +1,125 @@
+#!/usr/bin/env bash
+test_description="library reopen API"
+
+. $(dirname "$0")/test-lib.sh || exit 1
+
+add_email_corpus
+
+cat <<EOF > c_head
+#include <string.h>
+#include <stdlib.h>
+#include <notmuch-test.h>
+
+int main (int argc, char** argv)
+{
+   notmuch_database_t *db;
+   char *val;
+   notmuch_status_t stat;
+   notmuch_database_mode_t mode = NOTMUCH_DATABASE_MODE_READ_ONLY;
+
+   char *msg = NULL;
+
+   for (int i = 1; i < argc; i++)
+      if (strcmp (argv[i], "%NULL%") == 0) argv[i] = NULL;
+
+   if (argv[2] && (argv[2][0] == 'w' || argv[2][0] == 'W'))
+     mode = NOTMUCH_DATABASE_MODE_READ_WRITE;
+
+   stat = notmuch_database_open_with_config (argv[1],
+					     mode,
+					     argv[3],
+					     argv[4],
+					     &db,
+					     &msg);
+   if (stat != NOTMUCH_STATUS_SUCCESS) {
+     fprintf (stderr, "error opening database: %d %s\n", stat, msg ? msg : "");
+     exit (1);
+   }
+EOF
+
+cat <<EOF > c_tail
+   EXPECT0(notmuch_database_destroy(db));
+}
+EOF
+
+# The sequence of tests is important here
+
+test_begin_subtest "notmuch_database_reopen (read=>write)"
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} read ${NOTMUCH_CONFIG}
+{
+   EXPECT0(notmuch_database_reopen (db, NOTMUCH_DATABASE_MODE_READ_WRITE));
+   EXPECT0(notmuch_database_set_config (db, "test.key1", "testvalue1"));
+   EXPECT0(notmuch_database_set_config (db, "test.key2", "testvalue2"));
+   EXPECT0(notmuch_database_get_config (db, "test.key1", &val));
+   printf("test.key1 = %s\n", val);
+   EXPECT0(notmuch_database_get_config (db, "test.key2", &val));
+   printf("test.key2 = %s\n", val);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+test.key1 = testvalue1
+test.key2 = testvalue2
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "notmuch_database_reopen (read=>read)"
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} read ${NOTMUCH_CONFIG}
+{
+   EXPECT0(notmuch_database_reopen (db, NOTMUCH_DATABASE_MODE_READ_ONLY));
+   EXPECT0(notmuch_database_get_config (db, "test.key1", &val));
+   printf("test.key1 = %s\n", val);
+   EXPECT0(notmuch_database_get_config (db, "test.key2", &val));
+   printf("test.key2 = %s\n", val);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+test.key1 = testvalue1
+test.key2 = testvalue2
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "notmuch_database_reopen (write=>read)"
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} write ${NOTMUCH_CONFIG}
+{
+   EXPECT0(notmuch_database_reopen (db, NOTMUCH_DATABASE_MODE_READ_ONLY));
+   EXPECT0(notmuch_database_get_config (db, "test.key1", &val));
+   printf("test.key1 = %s\n", val);
+   EXPECT0(notmuch_database_get_config (db, "test.key2", &val));
+   printf("test.key2 = %s\n", val);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+test.key1 = testvalue1
+test.key2 = testvalue2
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "notmuch_database_reopen (write=>write)"
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} write ${NOTMUCH_CONFIG}
+{
+   EXPECT0(notmuch_database_reopen (db, NOTMUCH_DATABASE_MODE_READ_WRITE));
+   EXPECT0(notmuch_database_set_config (db, "test.key3", "testvalue3"));
+   EXPECT0(notmuch_database_get_config (db, "test.key1", &val));
+   printf("test.key1 = %s\n", val);
+   EXPECT0(notmuch_database_get_config (db, "test.key2", &val));
+   printf("test.key2 = %s\n", val);
+   EXPECT0(notmuch_database_get_config (db, "test.key3", &val));
+   printf("test.key3 = %s\n", val);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+test.key1 = testvalue1
+test.key2 = testvalue2
+test.key3 = testvalue3
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_done