Adding support for mocking debugged traits (#25)

* Adding support for mocking debugged traits

* Rather than panic on printing, we will let the user control the print message

Co-authored-by: david <[email protected]>

Author: David DeSimone

mock_derive/src/lib.rs

@@ -504,6 +504,9 @@ fn parse_trait(trait_block: syn::ItemTrait, raw_trait: &syn::Item) -> proc_macro
             }
         }
     }
+
+    fields.extend(quote! { print_string: ::std::sync::Mutex<Option<String>>, });
+    ctor.extend(quote! { print_string : ::std::sync::Mutex::new(None), });
 
     let mock_method_body = generate_mock_method_body(&pubtok, &mock_method_name);
     let static_struct_name = concat!("STATIC__", trait_name);
@@ -536,6 +539,21 @@ fn parse_trait(trait_block: syn::ItemTrait, raw_trait: &syn::Item) -> proc_macro
             #fields
         }
 
+        #[allow(dead_code)]
+        #[allow(non_camel_case_types)]
+        impl #generics ::std::fmt::Debug for #impl_name #generics #where_clause {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                // panic!("Printing mocks is not supported. Do not call println on mocks.");
+                let print_string = self.print_string.lock().unwrap();
+                let mut message = "This is the default message for a mock object. You can set the print behavior via a call to 'set_print_string'";
+                if print_string.as_ref().is_some() {
+                    message = print_string.as_ref().unwrap();
+                }
+
+                f.pad(&message)
+            }
+        }
+
         // Your mocks may not use all of these functions, so it's fine to allow
         // dead code in this impl block.
         #[allow(dead_code)]
@@ -546,6 +564,11 @@ fn parse_trait(trait_block: syn::ItemTrait, raw_trait: &syn::Item) -> proc_macro
             pub fn new() -> #impl_name #generics {
                 #impl_name { #ctor }
             }
+
+            pub fn set_print_string(&self, arg_string: String) {
+                let mut print_string = self.print_string.lock().unwrap();
+                *print_string = Some(arg_string);
+            }
         }
 
         #mock_method_body

tests/src/advanced_traits.rs

@@ -25,6 +25,8 @@ SOFTWARE.
 use mock_derive::mock;
 use export;
 
+use std::fmt::Debug;
+
 #[mock]
 trait Base {
     fn add(&self, x: i32, y: usize) -> usize;
@@ -89,6 +91,11 @@ trait UnsafeStaticMock {
     unsafe fn st_method() -> usize;
 }
 
+#[mock]
+trait DebuggedTrait : Debug {
+    fn foo(&self);
+}
+
 // @TODO support
 /*
 trait BaseG<T> {
@@ -99,6 +106,13 @@ trait DerivedG : BaseG<usize> {
 };
 */
 
+#[test]
+fn print_trait() {
+    let mock_debugged = MockDebuggedTrait::new();
+    mock_debugged.set_print_string(String::from("Hello Mocks"));
+    println!("{:?}", mock_debugged);
+}
+
 #[test]
 fn mock_derived() {
     let mut mock_derived = MockDerived::new();