Provide Position to debug.

src/engine.rs

@@ -4,7 +4,8 @@ use crate::ast::{Expr, FnCallExpr, Ident, IdentX, ReturnType, Stmt};
 use crate::dynamic::{map_std_type_name, AccessMode, Union, Variant};
 use crate::fn_call::run_builtin_op_assignment;
 use crate::fn_native::{
-    CallableFunction, IteratorFn, OnPrintCallback, OnProgressCallback, OnVarCallback,
+    CallableFunction, IteratorFn, OnDebugCallback, OnPrintCallback, OnProgressCallback,
+    OnVarCallback,
 };
 use crate::module::NamespaceRef;
 use crate::optimize::OptimizationLevel;
@@ -626,7 +627,7 @@ pub struct Engine {
     /// Callback closure for implementing the `print` command.
     pub(crate) print: OnPrintCallback,
     /// Callback closure for implementing the `debug` command.
-    pub(crate) debug: OnPrintCallback,
+    pub(crate) debug: OnDebugCallback,
     /// Callback closure for progress reporting.
     pub(crate) progress: Option<OnProgressCallback>,
 
@@ -677,7 +678,7 @@ pub fn is_anonymous_fn(fn_name: &str) -> bool {
     fn_name.starts_with(FN_ANONYMOUS)
 }
 
-/// Print/debug to stdout
+/// Print to stdout
 #[inline(always)]
 fn default_print(_s: &str) {
     #[cfg(not(feature = "no_std"))]
@@ -685,6 +686,14 @@ fn default_print(_s: &str) {
     println!("{}", _s);
 }
 
+/// Debug to stdout
+#[inline(always)]
+fn default_debug(_s: &str, _pos: Position) {
+    #[cfg(not(feature = "no_std"))]
+    #[cfg(not(target_arch = "wasm32"))]
+    println!("{:?} | {}", _pos, _s);
+}
+
 /// Search for a module within an imports stack.
 /// [`Position`] in [`EvalAltResult`] is [`None`][Position::None] and must be set afterwards.
 pub fn search_imports(
@@ -741,7 +750,7 @@ impl Engine {
 
             // default print/debug implementations
             print: Box::new(default_print),
-            debug: Box::new(default_print),
+            debug: Box::new(default_debug),
 
             // progress callback
             progress: None,
@@ -797,7 +806,7 @@ impl Engine {
             resolve_var: None,
 
             print: Box::new(|_| {}),
-            debug: Box::new(|_| {}),
+            debug: Box::new(|_, _| {}),
             progress: None,
 
             optimization_level: if cfg!(feature = "no_optimize") {

src/engine_api.rs

@@ -1808,16 +1808,21 @@ impl Engine {
     ///
     /// // Override action of 'print' function
     /// let logger = result.clone();
-    /// engine.on_debug(move |s| logger.write().unwrap().push_str(s));
+    /// engine.on_debug(move |s, pos| logger.write().unwrap().push_str(
+    ///                                 &format!("{:?} > {}", pos, s)
+    ///                               ));
     ///
-    /// engine.consume(r#"debug("hello");"#)?;
+    /// engine.consume(r#"let x = "hello"; debug(x);"#)?;
     ///
-    /// assert_eq!(*result.read().unwrap(), r#""hello""#);
+    /// assert_eq!(*result.read().unwrap(), r#"1:18 > "hello""#);
     /// # Ok(())
     /// # }
     /// ```
     #[inline(always)]
-    pub fn on_debug(&mut self, callback: impl Fn(&str) + SendSync + 'static) -> &mut Self {
+    pub fn on_debug(
+        &mut self,
+        callback: impl Fn(&str, Position) + SendSync + 'static,
+    ) -> &mut Self {
         self.debug = Box::new(callback);
         self
     }

src/fn_call.rs

@@ -211,13 +211,16 @@ impl Engine {
                     false,
                 ),
                 KEYWORD_DEBUG => (
-                    (self.debug)(result.as_str().map_err(|typ| {
-                        EvalAltResult::ErrorMismatchOutputType(
-                            self.map_type_name(type_name::<ImmutableString>()).into(),
-                            typ.into(),
-                            pos,
-                        )
-                    })?)
+                    (self.debug)(
+                        result.as_str().map_err(|typ| {
+                            EvalAltResult::ErrorMismatchOutputType(
+                                self.map_type_name(type_name::<ImmutableString>()).into(),
+                                typ.into(),
+                                pos,
+                            )
+                        })?,
+                        pos,
+                    )
                     .into(),
                     false,
                 ),

src/fn_native.rs

@@ -356,7 +356,14 @@ pub type OnProgressCallback = Box<dyn Fn(u64) -> Option<Dynamic> + Send + Sync +
 pub type OnPrintCallback = Box<dyn Fn(&str) + 'static>;
 /// A standard callback function for printing.
 #[cfg(feature = "sync")]
-pub type OnPrintCallback<T, R> = Box<dyn Fn(&str) + Send + Sync + 'static>;
+pub type OnPrintCallback = Box<dyn Fn(&str) + Send + Sync + 'static>;
+
+/// A standard callback function for debugging.
+#[cfg(not(feature = "sync"))]
+pub type OnDebugCallback = Box<dyn Fn(&str, Position) + 'static>;
+/// A standard callback function for debugging.
+#[cfg(feature = "sync")]
+pub type OnDebugCallback = Box<dyn Fn(&str, Position) + Send + Sync + 'static>;
 
 /// A standard callback function for variable access.
 #[cfg(not(feature = "sync"))]