Improve "No constructor matches given arguments" message with more details (pythonnet#1143)

lostmsu · web-flow · commit 6d2f0bda8cfb · 2020-05-14T21:31:50.000+02:00
Similar to pythonnet#900, but for constructors (reuses the same code) Related issues: pythonnet#811, pythonnet#265, pythonnet#1116
diff --git a/src/runtime/constructorbinder.cs b/src/runtime/constructorbinder.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Reflection;
+using System.Text;
 
 namespace Python.Runtime
 {
@@ -93,7 +94,15 @@ internal object InvokeRaw(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info)
 
                 if (binding == null)
                 {
-                    Exceptions.SetError(Exceptions.TypeError, "no constructor matches given arguments");
+                    var errorMessage = new StringBuilder("No constructor matches given arguments");
+                    if (info != null && info.IsConstructor && info.DeclaringType != null)
+                    {
+                        errorMessage.Append(" for ").Append(info.DeclaringType.Name);
+                    }
+
+                    errorMessage.Append(": ");
+                    AppendArgumentTypes(to: errorMessage, args);
+                    Exceptions.SetError(Exceptions.TypeError, errorMessage.ToString());
                     return null;
                 }
             }
diff --git a/src/runtime/methodbinder.cs b/src/runtime/methodbinder.cs
@@ -599,6 +599,40 @@ internal virtual IntPtr Invoke(IntPtr inst, IntPtr args, IntPtr kw, MethodBase i
             return Invoke(inst, args, kw, info, null);
         }
 
+        protected static void AppendArgumentTypes(StringBuilder to, IntPtr args)
+        {
+            long argCount = Runtime.PyTuple_Size(args);
+            to.Append("(");
+            for (long argIndex = 0; argIndex < argCount; argIndex++)
+            {
+                var arg = Runtime.PyTuple_GetItem(args, argIndex);
+                if (arg != IntPtr.Zero)
+                {
+                    var type = Runtime.PyObject_Type(arg);
+                    if (type != IntPtr.Zero)
+                    {
+                        try
+                        {
+                            var description = Runtime.PyObject_Unicode(type);
+                            if (description != IntPtr.Zero)
+                            {
+                                to.Append(Runtime.GetManagedString(description));
+                                Runtime.XDecref(description);
+                            }
+                        }
+                        finally
+                        {
+                            Runtime.XDecref(type);
+                        }
+                    }
+                }
+
+                if (argIndex + 1 < argCount)
+                    to.Append(", ");
+            }
+            to.Append(')');
+        }
+
         internal virtual IntPtr Invoke(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, MethodInfo[] methodinfo)
         {
             Binding binding = Bind(inst, args, kw, info, methodinfo);
@@ -613,29 +647,8 @@ internal virtual IntPtr Invoke(IntPtr inst, IntPtr args, IntPtr kw, MethodBase i
                     value.Append($" for {methodinfo[0].Name}");
                 }
 
-                long argCount = Runtime.PyTuple_Size(args);
-                value.Append(": (");
-                for(long argIndex = 0; argIndex < argCount; argIndex++) {
-                    var arg = Runtime.PyTuple_GetItem(args, argIndex);
-                    if (arg != IntPtr.Zero) {
-                        var type = Runtime.PyObject_Type(arg);
-                        if (type != IntPtr.Zero) {
-                            try {
-                                var description = Runtime.PyObject_Unicode(type);
-                                if (description != IntPtr.Zero) {
-                                    value.Append(Runtime.GetManagedString(description));
-                                    Runtime.XDecref(description);
-                                }
-                            } finally {
-                                Runtime.XDecref(type);
-                            }
-                        }
-                    }
-
-                    if (argIndex + 1 < argCount)
-                        value.Append(", ");
-                }
-                value.Append(')');
+                value.Append(": ");
+                AppendArgumentTypes(to: value, args);
                 Exceptions.SetError(Exceptions.TypeError, value.ToString());
                 return IntPtr.Zero;
             }

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,6 @@`
`1`	`1`	`using System;`
`2`	`2`	`using System.Reflection;`
	`3`	`+using System.Text;`
`3`	`4`
`4`	`5`	`namespace Python.Runtime`
`5`	`6`	`{`
`@@ -93,7 +94,15 @@ internal object InvokeRaw(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info)`
`93`	`94`
`94`	`95`	`if (binding == null)`
`95`	`96`	`{`
`96`		`- Exceptions.SetError(Exceptions.TypeError, "no constructor matches given arguments");`
	`97`	`+ var errorMessage = new StringBuilder("No constructor matches given arguments");`
	`98`	`+ if (info != null && info.IsConstructor && info.DeclaringType != null)`
	`99`	`+ {`
	`100`	`+ errorMessage.Append(" for ").Append(info.DeclaringType.Name);`
	`101`	`+ }`
	`102`	`+`
	`103`	`+ errorMessage.Append(": ");`
	`104`	`+ AppendArgumentTypes(to: errorMessage, args);`
	`105`	`+ Exceptions.SetError(Exceptions.TypeError, errorMessage.ToString());`
`97`	`106`	`return null;`
`98`	`107`	`}`
`99`	`108`	`}`