Add debugging interface.

src/api/call_fn.rs

@@ -155,6 +155,10 @@ impl Engine {
     ) -> RhaiResult {
         let state = &mut EvalState::new();
         let global = &mut GlobalRuntimeState::new();
+
+        #[cfg(feature = "debugging")]
+        global.debugger.activate(self.debugger.is_some());
+
         let statements = ast.statements();
 
         let orig_scope_len = scope.len();

src/api/eval.rs

@@ -186,6 +186,9 @@ impl Engine {
     ) -> RhaiResultOf<T> {
         let global = &mut GlobalRuntimeState::new();
 
+        #[cfg(feature = "debugging")]
+        global.debugger.activate(self.debugger.is_some());
+
         let result = self.eval_ast_with_scope_raw(scope, global, ast, 0)?;
 
         let typ = self.map_type_name(result.type_name());

src/api/events.rs

@@ -64,7 +64,7 @@ impl Engine {
         self.resolve_var = Some(Box::new(callback));
         self
     }
-    /// _(internals)_ Provide a callback that will be invoked during parsing to remap certain tokens.
+    /// _(internals)_ Register a callback that will be invoked during parsing to remap certain tokens.
     /// Exported under the `internals` feature only.
     ///
     /// # Callback Function Signature
@@ -261,4 +261,22 @@ impl Engine {
         self.debug = Some(Box::new(callback));
         self
     }
+    /// _(debugging)_ Register a callback for debugging.
+    /// Exported under the `debugging` feature only.
+    #[cfg(feature = "debugging")]
+    #[inline(always)]
+    pub fn on_debugger(
+        &mut self,
+        callback: impl Fn(
+                &mut EvalContext,
+                crate::ast::ASTNode,
+                Option<&str>,
+                Position,
+            ) -> crate::eval::DebuggerCommand
+            + SendSync
+            + 'static,
+    ) -> &mut Self {
+        self.debugger = Some(Box::new(callback));
+        self
+    }
 }

src/api/run.rs

@@ -44,8 +44,10 @@ impl Engine {
     /// Evaluate an [`AST`] with own scope, returning any error (if any).
     #[inline]
     pub fn run_ast_with_scope(&self, scope: &mut Scope, ast: &AST) -> RhaiResultOf<()> {
+        let state = &mut EvalState::new();
         let global = &mut GlobalRuntimeState::new();
-        let mut state = EvalState::new();
+        #[cfg(feature = "debugging")]
+        global.debugger.activate(self.debugger.is_some());
         global.source = ast.source_raw().clone();
 
         #[cfg(not(feature = "no_module"))]
@@ -64,7 +66,7 @@ impl Engine {
             } else {
                 &lib
             };
-            self.eval_global_statements(scope, global, &mut state, statements, lib, 0)?;
+            self.eval_global_statements(scope, global, state, statements, lib, 0)?;
         }
         Ok(())
     }