Support multiple exit codes

..with more specific error enums.

taskchampion/src/errors.rs

@@ -1,6 +1,9 @@
 use thiserror::Error;
+
 #[derive(Debug, Error, Eq, PartialEq, Clone)]
+#[non_exhaustive]
+/// Errors returned from taskchampion operations
 pub enum Error {
-    #[error("Task Database Error: {}", _0)]
-    DbError(String),
+    #[error("Task Database Error: {0}")]
+    Database(String),
 }

taskchampion/src/lib.rs

@@ -40,6 +40,7 @@ mod taskdb;
 mod utils;
 mod workingset;
 
+pub use errors::Error;
 pub use replica::Replica;
 pub use server::{Server, ServerConfig};
 pub use storage::StorageConfig;

taskchampion/src/replica.rs

@@ -113,7 +113,7 @@ impl Replica {
         // check that it already exists; this is a convenience check, as the task may already exist
         // when this Create operation is finally sync'd with operations from other replicas
         if self.taskdb.get_task(uuid)?.is_none() {
-            return Err(Error::DbError(format!("Task {} does not exist", uuid)).into());
+            return Err(Error::Database(format!("Task {} does not exist", uuid)).into());
         }
         self.taskdb.apply(Operation::Delete { uuid })?;
         trace!("task {} deleted", uuid);

taskchampion/src/taskdb.rs

@@ -49,12 +49,12 @@ impl TaskDb {
             Operation::Create { uuid } => {
                 // insert if the task does not already exist
                 if !txn.create_task(*uuid)? {
-                    return Err(Error::DbError(format!("Task {} already exists", uuid)).into());
+                    return Err(Error::Database(format!("Task {} already exists", uuid)).into());
                 }
             }
             Operation::Delete { ref uuid } => {
                 if !txn.delete_task(*uuid)? {
-                    return Err(Error::DbError(format!("Task {} does not exist", uuid)).into());
+                    return Err(Error::Database(format!("Task {} does not exist", uuid)).into());
                 }
             }
             Operation::Update {
@@ -71,7 +71,7 @@ impl TaskDb {
                     };
                     txn.set_task(*uuid, task)?;
                 } else {
-                    return Err(Error::DbError(format!("Task {} does not exist", uuid)).into());
+                    return Err(Error::Database(format!("Task {} does not exist", uuid)).into());
                 }
             }
         }