lib/config: add notmuch_config_key_{get,set}

By using an enum we can have better error detection than copy pasting
key strings around.

The question of what layer this belongs in is a bit
tricky. Historically most of the keys are defined by the CLI. On the
other hand features like excludes are supported in the
library/bindings, and it makes sense to configure them from the
library as well.

The somewhat long prefix for notmuch_config_t is to avoid collisions
with the existing usage in notmuch-client.h.

lib/config.cc

@@ -279,3 +279,37 @@ _notmuch_config_load_from_file (notmuch_database_t *notmuch,
  DONE:
     return status;
 }
+
+const char *
+_notmuch_config_key_to_string (notmuch_config_key_t key) {
+    switch (key) {
+    case NOTMUCH_CONFIG_DATABASE_PATH:
+	return "database.path";
+    case NOTMUCH_CONFIG_EXCLUDE_TAGS:
+	return "search.exclude_tags";
+    case NOTMUCH_CONFIG_NEW_TAGS:
+	return "new.tags";
+    case NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS:
+	return "maildir.synchronize_flags";
+    case NOTMUCH_CONFIG_PRIMARY_EMAIL:
+	return "user.primary_email";
+    case NOTMUCH_CONFIG_OTHER_EMAIL:
+	return "user.other_email";
+    case NOTMUCH_CONFIG_USER_NAME:
+	return "user.name";
+    default:
+	return NULL;
+    }
+}
+
+const char *
+notmuch_config_get (notmuch_database_t *notmuch, notmuch_config_key_t key) {
+
+    return _notmuch_string_map_get (notmuch->config, _notmuch_config_key_to_string (key));
+}
+
+notmuch_status_t
+notmuch_config_set (notmuch_database_t *notmuch, notmuch_config_key_t key, const char *val) {
+
+    return notmuch_database_set_config (notmuch, _notmuch_config_key_to_string (key), val);
+}

lib/notmuch.h

@@ -2325,6 +2325,11 @@ notmuch_filenames_destroy (notmuch_filenames_t *filenames);
  * set config 'key' to 'value'
  *
  * @since libnotmuch 4.4 (notmuch 0.23)
+ * @retval #NOTMUCH_STATUS_READ_ONLY_DATABASE: Database was opened in
+ *	read-only mode so message cannot be modified.
+ * @retval #NOTMUCH_STATUS_XAPIAN_EXCEPTION: an exception was thrown
+ *      accessing the database.
+ * @retval #NOTMUCH_STATUS_SUCCESS
  */
 notmuch_status_t
 notmuch_database_set_config (notmuch_database_t *db, const char *key, const char *value);
@@ -2339,6 +2344,7 @@ notmuch_database_set_config (notmuch_database_t *db, const char *key, const char
  * caller.
  *
  * @since libnotmuch 4.4 (notmuch 0.23)
+ *
  */
 notmuch_status_t
 notmuch_database_get_config (notmuch_database_t *db, const char *key, char **value);
@@ -2400,6 +2406,56 @@ void
 notmuch_config_list_destroy (notmuch_config_list_t *config_list);
 
 
+/**
+ * Configuration keys known to libnotmuch
+ */
+typedef enum _notmuch_config_key {
+    NOTMUCH_CONFIG_FIRST,
+    NOTMUCH_CONFIG_DATABASE_PATH = NOTMUCH_CONFIG_FIRST,
+    NOTMUCH_CONFIG_EXCLUDE_TAGS,
+    NOTMUCH_CONFIG_NEW_TAGS,
+    NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS,
+    NOTMUCH_CONFIG_PRIMARY_EMAIL,
+    NOTMUCH_CONFIG_OTHER_EMAIL,
+    NOTMUCH_CONFIG_USER_NAME,
+    NOTMUCH_CONFIG_LAST
+} notmuch_config_key_t;
+
+/**
+ * get a configuration value from an open database.
+ *
+ * This value reflects all configuration information given at the time
+ * the database was opened.
+ *
+ * @param[in] notmuch database
+ * @param[in] key configuration key
+ *
+ * @since libnotmuch 5.4 (notmuch 0.32)
+ *
+ * @retval NULL if 'key' unknown or if no value is known for
+ *         'key'.  Otherwise returns a string owned by notmuch which should
+ *         not be modified nor freed by the caller.
+ */
+const char *
+notmuch_config_get (notmuch_database_t *notmuch, notmuch_config_key_t key);
+
+/**
+ * set a configuration value from in an open database.
+ *
+ * This value reflects all configuration information given at the time
+ * the database was opened.
+ *
+ * @param[in,out] notmuch database open read/write
+ * @param[in] key configuration key
+ * @param[in] val configuration value
+ *
+ * @since libnotmuch 5.4 (notmuch 0.32)
+ *
+ * @retval returns any return value for notmuch_database_set_config.
+ */
+notmuch_status_t
+notmuch_config_set (notmuch_database_t *notmuch, notmuch_config_key_t key, const char *val);
+
 /**
  * get the current default indexing options for a given database.
  *

test/T590-libconfig.sh

@@ -201,6 +201,44 @@ EOF
 test_expect_equal_file EXPECTED OUTPUT
 restore_database
 
+backup_database
+test_begin_subtest "get config by key"
+notmuch config set test.key1 overridden
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} ${NOTMUCH_CONFIG}
+{
+   printf("before = %s\n", notmuch_config_get (db, NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS));
+   EXPECT0(notmuch_database_set_config (db, "maildir.synchronize_flags", "false"));
+   printf("after = %s\n", notmuch_config_get (db, NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS));
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+before = true
+after = false
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+restore_database
+
+backup_database
+test_begin_subtest "set config by key"
+notmuch config set test.key1 overridden
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR} ${NOTMUCH_CONFIG}
+{
+   printf("before = %s\n", notmuch_config_get (db, NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS));
+   EXPECT0(notmuch_config_set (db, NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS, "false"));
+   printf("after = %s\n", notmuch_config_get (db, NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS));
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+before = true
+after = false
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+restore_database
+
 backup_database
 test_begin_subtest "override config from \${NOTMUCH_CONFIG}"
 notmuch config set test.key1 overridden