allow task setters to return error values

integration-tests/src/bindings_tests/task.c

@@ -41,7 +41,7 @@ static void test_task_free_mutable_task(void) {
     TCUuid uuid = tc_task_get_uuid(task);
 
     tc_task_to_mut(task, rep);
-    TEST_ASSERT_TRUE(tc_task_set_status(task, TC_STATUS_DELETED));
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_set_status(task, TC_STATUS_DELETED));
     TEST_ASSERT_EQUAL(TC_STATUS_DELETED, tc_task_get_status(task));
 
     tc_task_free(task); // implicitly converts to immut
@@ -68,7 +68,7 @@ static void test_task_get_set_status(void) {
     TEST_ASSERT_EQUAL(TC_STATUS_PENDING, tc_task_get_status(task));
 
     tc_task_to_mut(task, rep);
-    TEST_ASSERT_TRUE(tc_task_set_status(task, TC_STATUS_DELETED));
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_set_status(task, TC_STATUS_DELETED));
     TEST_ASSERT_EQUAL(TC_STATUS_DELETED, tc_task_get_status(task)); // while mut
     tc_task_to_immut(task);
     TEST_ASSERT_EQUAL(TC_STATUS_DELETED, tc_task_get_status(task)); // while immut
@@ -92,7 +92,7 @@ static void test_task_get_set_description(void) {
     TCString *desc;
 
     tc_task_to_mut(task, rep);
-    tc_task_set_description(task, tc_string_borrow("updated"));
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_set_description(task, tc_string_borrow("updated")));
 
     TEST_ASSERT_TRUE(desc = tc_task_get_description(task));
     TEST_ASSERT_NOT_NULL(desc);
@@ -127,9 +127,9 @@ static void test_task_start_stop_is_active(void) {
     tc_task_to_mut(task, rep);
 
     TEST_ASSERT_FALSE(tc_task_is_active(task));
-    tc_task_start(task);
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_start(task));
     TEST_ASSERT_TRUE(tc_task_is_active(task));
-    tc_task_stop(task);
+    TEST_ASSERT_EQUAL(TC_RESULT_TRUE, tc_task_stop(task));
     TEST_ASSERT_FALSE(tc_task_is_active(task));
 
     tc_task_free(task);

lib/src/result.rs

@@ -1,10 +1,11 @@
+// TODO: make true = 1, false = 0, error = -1
 /// A result combines a boolean success value with
 /// an error response.  It is equivalent to `Result<bool, ()>`.
 /// cbindgen:prefix-with-name
 /// cbindgen:rename-all=ScreamingSnakeCase
 #[repr(C)]
 pub enum TCResult {
-    True,
+    Error = -1,
-    False,
+    False = 0,
-    Error,
+    True = 1,
 }

lib/src/task.rs

@@ -1,4 +1,6 @@
-use crate::{replica::TCReplica, status::TCStatus, string::TCString, uuid::TCUuid};
+use crate::{
+    replica::TCReplica, result::TCResult, status::TCStatus, string::TCString, uuid::TCUuid,
+};
 use std::ops::Deref;
 use taskchampion::{Task, TaskMut};
 
@@ -113,7 +115,8 @@ impl From<Task> for TCTask {
     }
 }
 
-/// Utility function to get a shared reference to the underlying Task.
+/// Utility function to get a shared reference to the underlying Task.  All Task getters
+/// are error-free, so this does not handle errors.
 fn wrap<'a, T, F>(task: *const TCTask, f: F) -> T
 where
     F: FnOnce(&Task) -> T,
@@ -131,8 +134,9 @@ where
 }
 
 /// Utility function to get a mutable reference to the underlying Task.  The
-/// TCTask must be mutable.
+/// TCTask must be mutable.  The inner function may use `?` syntax to return an
-fn wrap_mut<'a, T, F>(task: *mut TCTask, f: F) -> T
+/// error, which will be represented with the `err_value` returned to C.
+fn wrap_mut<'a, T, F>(task: *mut TCTask, f: F, err_value: T) -> T
 where
     F: FnOnce(&mut TaskMut) -> anyhow::Result<T>,
 {
@@ -145,8 +149,13 @@ where
         TCTask::Mutable(ref mut t, _) => t,
         TCTask::Invalid => unreachable!(),
     };
+    match f(task) {
+        Ok(rv) => rv,
+        Err(e) => {
             // TODO: add TCTask error handling, like replica
-    f(task).unwrap()
+            err_value
+        }
+    }
 }
 
 /// Convert an immutable task into a mutable task.
@@ -238,31 +247,39 @@ pub extern "C" fn tc_task_is_active<'a>(task: *const TCTask) -> bool {
 
 /// Set a mutable task's status.
 ///
-/// Returns false on error.
+/// Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
 #[no_mangle]
-pub extern "C" fn tc_task_set_status<'a>(task: *mut TCTask, status: TCStatus) -> bool {
+pub extern "C" fn tc_task_set_status<'a>(task: *mut TCTask, status: TCStatus) -> TCResult {
-    wrap_mut(task, |task| {
+    wrap_mut(
+        task,
+        |task| {
             task.set_status(status.into())?;
-        Ok(true)
+            Ok(TCResult::True)
-    })
+        },
+        TCResult::Error,
+    )
 }
 
 /// Set a mutable task's description.
 ///
-/// Returns false on error.
+/// Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
 #[no_mangle]
 pub extern "C" fn tc_task_set_description<'a>(
     task: *mut TCTask,
     description: *mut TCString,
-) -> bool {
+) -> TCResult {
     // SAFETY:
     //  - tcstring is not NULL (promised by caller)
     //  - caller is exclusive owner of tcstring (implicitly promised by caller)
     let description = unsafe { TCString::from_arg(description) };
-    wrap_mut(task, |task| {
+    wrap_mut(
+        task,
+        |task| {
             task.set_description(description.as_str()?.to_string())?;
-        Ok(true)
+            Ok(TCResult::True)
-    })
+        },
+        TCResult::Error,
+    )
 }
 
 // TODO: tc_task_set_description
@@ -272,24 +289,32 @@ pub extern "C" fn tc_task_set_description<'a>(
 
 /// Start a task.
 ///
-/// TODO: error
+/// Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
 #[no_mangle]
-pub extern "C" fn tc_task_start<'a>(task: *mut TCTask) {
+pub extern "C" fn tc_task_start<'a>(task: *mut TCTask) -> TCResult {
-    wrap_mut(task, |task| {
+    wrap_mut(
+        task,
+        |task| {
             task.start()?;
-        Ok(())
+            Ok(TCResult::True)
-    })
+        },
+        TCResult::Error,
+    )
 }
 
 /// Stop a task.
 ///
-/// TODO: error
+/// Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
 #[no_mangle]
-pub extern "C" fn tc_task_stop<'a>(task: *mut TCTask) {
+pub extern "C" fn tc_task_stop<'a>(task: *mut TCTask) -> TCResult {
-    wrap_mut(task, |task| {
+    wrap_mut(
+        task,
+        |task| {
             task.stop()?;
-        Ok(())
+            Ok(TCResult::True)
-    })
+        },
+        TCResult::Error,
+    )
 }
 
 // TODO: tc_task_done

lib/taskchampion.h

@@ -11,9 +11,9 @@
  * an error response.  It is equivalent to `Result<bool, ()>`.
  */
 typedef enum TCResult {
-  TC_RESULT_TRUE,
+  TC_RESULT_ERROR = -1,
-  TC_RESULT_FALSE,
+  TC_RESULT_FALSE = 0,
-  TC_RESULT_ERROR,
+  TC_RESULT_TRUE = 1,
 } TCResult;
 
 /**
@@ -258,30 +258,30 @@ bool tc_task_is_active(const struct TCTask *task);
 /**
  * Set a mutable task's status.
  *
- * Returns false on error.
+ * Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
  */
-bool tc_task_set_status(struct TCTask *task, enum TCStatus status);
+enum TCResult tc_task_set_status(struct TCTask *task, enum TCStatus status);
 
 /**
  * Set a mutable task's description.
  *
- * Returns false on error.
+ * Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
  */
-bool tc_task_set_description(struct TCTask *task, struct TCString *description);
+enum TCResult tc_task_set_description(struct TCTask *task, struct TCString *description);
 
 /**
  * Start a task.
  *
- * TODO: error
+ * Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
  */
-void tc_task_start(struct TCTask *task);
+enum TCResult tc_task_start(struct TCTask *task);
 
 /**
  * Stop a task.
  *
- * TODO: error
+ * Returns TC_RESULT_TRUE on success and TC_RESULT_ERROR on failure.
  */
-void tc_task_stop(struct TCTask *task);
+enum TCResult tc_task_stop(struct TCTask *task);
 
 /**
  * Free a task.  The given task must not be NULL.  The task must not be used after this function