add tc_task_add_tag and check errors

integration-tests/src/bindings_tests/task.c

@@ -136,6 +136,35 @@ static void test_task_start_stop_is_active(void) {
     tc_replica_free(rep);
 }
 
+// adding tags to a task works, and invalid tags are rejected
+static void task_task_add_tag(void) {
+    TCReplica *rep = tc_replica_new_in_memory();
+    TEST_ASSERT_NULL(tc_replica_error(rep));
+
+    TCTask *task = tc_replica_new_task(
+            rep,
+            TC_STATUS_PENDING,
+            tc_string_borrow("my task"));
+    TEST_ASSERT_NOT_NULL(task);
+
+    tc_task_to_mut(task, rep);
+
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_add_tag(task, tc_string_borrow("next")));
+
+    // invalid - synthetic tag
+    TEST_ASSERT_EQUAL(TC_RESULT_ERROR, tc_task_add_tag(task, tc_string_borrow("PENDING")));
+    // invald - not a valid tag string
+    TEST_ASSERT_EQUAL(TC_RESULT_ERROR, tc_task_add_tag(task, tc_string_borrow("my tag")));
+    // invald - not utf-8
+    TEST_ASSERT_EQUAL(TC_RESULT_ERROR, tc_task_add_tag(task, tc_string_borrow("\xf0\x28\x8c\x28")));
+
+    // TODO: check error messages
+    // TODO: test getting the tag
+
+    tc_task_free(task);
+    tc_replica_free(rep);
+}
+
 int task_tests(void) {
     UNITY_BEGIN();
     // each test case above should be named here, in order.
@@ -144,5 +173,6 @@ int task_tests(void) {
     RUN_TEST(test_task_get_set_status);
     RUN_TEST(test_task_get_set_description);
     RUN_TEST(test_task_start_stop_is_active);
+    RUN_TEST(task_task_add_tag);
     return UNITY_END();
 }

lib/src/task.rs

@@ -2,7 +2,8 @@ use crate::{
     replica::TCReplica, result::TCResult, status::TCStatus, string::TCString, uuid::TCUuid,
 };
 use std::ops::Deref;
-use taskchampion::{Task, TaskMut};
+use std::str::FromStr;
+use taskchampion::{Tag, Task, TaskMut};
 
 /// A task, as publicly exposed by this library.
 ///
@@ -282,7 +283,6 @@ pub extern "C" fn tc_task_set_description<'a>(
     )
 }
 
-// TODO: tc_task_set_description
 // TODO: tc_task_set_entry
 // TODO: tc_task_set_wait
 // TODO: tc_task_set_modified
@@ -319,7 +319,28 @@ pub extern "C" fn tc_task_stop<'a>(task: *mut TCTask) -> TCResult {
 
 // TODO: tc_task_done
 // TODO: tc_task_delete
-// TODO: tc_task_add_tag
+
+/// Add a tag to a mutable task.
+///
+/// Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
+#[no_mangle]
+pub extern "C" fn tc_task_add_tag<'a>(task: *mut TCTask, tag: *mut TCString) -> TCResult {
+    // SAFETY:
+    //  - tcstring is not NULL (promised by caller)
+    //  - caller is exclusive owner of tcstring (implicitly promised by caller)
+    let tcstring = unsafe { TCString::from_arg(tag) };
+    wrap_mut(
+        task,
+        |task| {
+            let tagstr = tcstring.as_str()?;
+            let tag = Tag::from_str(tagstr)?;
+            task.add_tag(&tag)?;
+            Ok(TCResult::True)
+        },
+        TCResult::Error,
+    )
+}
+
 // TODO: tc_task_remove_tag
 // TODO: tc_task_add_annotation
 // TODO: tc_task_remove_annotation

lib/taskchampion.h

@@ -283,6 +283,13 @@ enum TCResult tc_task_start(struct TCTask *task);
  */
 enum TCResult tc_task_stop(struct TCTask *task);
 
+/**
+ * Add a tag to a mutable task.
+ *
+ * Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
+ */
+enum TCResult tc_task_add_tag(struct TCTask *task, struct TCString *tag);
+
 /**
  * Free a task.  The given task must not be NULL.  The task must not be used after this function
  * returns, and must not be freed more than once.