gopy,bind: improve error reporting for python-incompatible methods and funcs

Author: cosnicolaou

_examples/gopyerrors/gopyerrors.go

@@ -0,0 +1,29 @@
+// Copyright 2020 The go-python Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// package gopyerrors contains functions that generate error
+// messages from gopy itself.
+package gopyerrors
+
+func NotErrorMany() (int, int) {
+	return 0, 0
+}
+
+func TooMany() (int, int, string) {
+	return 0, 1, "Hi"
+}
+
+func OK() (int, error) {
+	return 0, nil
+}
+
+type Struct struct{}
+
+func (s *Struct) NotErrorMany() (int, string) {
+	return 0, "Hi"
+}
+
+func (s *Struct) TooMany() (int, int, string) {
+	return 0, 1, "Hi"
+}

_examples/gopyerrors/test.py

@@ -0,0 +1,13 @@
+# Copyright 2020 go-python Authors.  All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# py2/py3 compat
+from __future__ import print_function
+
+import gopyerrors
+
+# This is empty, its only purpose is to have a test that catches
+# errors generated by the gopy itself.
+
+print("OK")

bind/symbols.go

@@ -559,6 +559,8 @@ func (sym *symtab) addSymbol(obj types.Object) error {
 			}
 			return sym.processTuple(sig.Results())
 		}
+		fmt.Printf("ignoring python incompatible function: %v.%v: %v: %v\n", pkg.Name(), obj.String(), sig.String(), err)
+
 	case *types.TypeName:
 		return sym.addType(obj, obj.Type())
 
@@ -1116,7 +1118,7 @@ func (sym *symtab) addMethod(pkg *types.Package, obj types.Object, t types.Type,
 	sig := t.Underlying().(*types.Signature)
 	_, _, _, err := isPyCompatFunc(sig)
 	if err != nil {
-		fmt.Printf("ignoring python incompatible method: %v.%v: %v: %v\n", pkg.Name(), obj.Name(), t.String(), err)
+		fmt.Printf("ignoring python incompatible method: %v.%v: %v: %v\n", pkg.Name(), obj.String(), t.String(), err)
 	}
 	if err == nil {
 		fn := types.ObjectString(obj, nil)

main_test.go

@@ -91,6 +91,34 @@ func TestGofmt(t *testing.T) {
 	}
 }
 
+func TestGoPyErrors(t *testing.T) {
+	pyvm := testBackends["py3"]
+	workdir, err := ioutil.TempDir("", "gopy-")
+	if err != nil {
+		t.Fatalf("could not create workdir: %v\n", err)
+	}
+	t.Logf("pyvm: %s making work dir: %s\n", pyvm, workdir)
+	defer os.RemoveAll(workdir)
+
+	curPkgPath := reflect.TypeOf(pkg{}).PkgPath()
+	fpath := filepath.Join(curPkgPath, "_examples/gopyerrors")
+	cmd := exec.Command("go", "run", ".", "gen", "-vm="+pyvm, "-output="+workdir, fpath)
+	t.Logf("running: %v\n", cmd.Args)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("could not run %v: %+v\n", strings.Join(cmd.Args, " "), err)
+	}
+	contains := `--- Processing package: github.com/go-python/gopy/_examples/gopyerrors ---
+ignoring python incompatible function: gopyerrors.func github.com/go-python/gopy/_examples/gopyerrors.NotErrorMany() (int, int): func() (int, int): gopy: second result value must be of type error: func() (int, int)
+ignoring python incompatible method: gopyerrors.func (*github.com/go-python/gopy/_examples/gopyerrors.Struct).NotErrorMany() (int, string): func() (int, string): gopy: second result value must be of type error: func() (int, string)
+ignoring python incompatible method: gopyerrors.func (*github.com/go-python/gopy/_examples/gopyerrors.Struct).TooMany() (int, int, string): func() (int, int, string): gopy: too many results to return: func() (int, int, string)
+ignoring python incompatible function: gopyerrors.func github.com/go-python/gopy/_examples/gopyerrors.TooMany() (int, int, string): func() (int, int, string): gopy: too many results to return: func() (int, int, string)
+`
+	if got, want := string(out), contains; !strings.Contains(got, want) {
+		t.Fatalf("%v does not contain %v\n", got, want)
+	}
+}
+
 func TestHi(t *testing.T) {
 	// t.Parallel()
 	path := "_examples/hi"