refactor(engine): move lib.rs items to {command_sets,doc_state,error,history,interaction,prefs,sanity,session,session/documents,session/edit,session/execute,session/undo}.rs

crates/engine/src/error.rs

@@ -0,0 +1,40 @@
+use super::*;
+
+#[derive(Debug, thiserror::Error)]
+pub enum EngineError {
+    #[error("unknown command `{0}`")]
+    UnknownCommand(String),
+    /// An unknown command id, with the command id it most likely misspells.
+    #[error("unknown command `{0}`; did you mean `{1}`?")]
+    UnknownCommandNear(String, String),
+    #[error("command `{0}` is not available right now: {1}")]
+    Disabled(String, String),
+    #[error("invalid parameters for `{cmd}`: {msg}")]
+    BadParams { cmd: String, msg: String },
+    #[error("no active document")]
+    NoDocument,
+    #[error("no such object {0}")]
+    NoNode(NodeId),
+    #[error("{0}")]
+    Other(String),
+    /// The caller asked for the command to stop ([`cancel`]). It changed nothing.
+    #[error("cancelled; nothing was changed")]
+    Cancelled,
+    /// A bug: the command panicked. The document was rolled back to its state before the command.
+    #[error("internal error in `{cmd}`: {msg} (the document was left as it was before; please report this bug)")]
+    Internal { cmd: String, msg: String },
+}
+
+impl From<cancel::Cancelled> for EngineError {
+    fn from(_: cancel::Cancelled) -> Self {
+        EngineError::Cancelled
+    }
+}
+
+impl From<vectorcraft_doc::DocError> for EngineError {
+    fn from(e: vectorcraft_doc::DocError) -> Self {
+        EngineError::Other(e.to_string())
+    }
+}
+
+pub type Result<T> = std::result::Result<T, EngineError>;