Merge pull request #1 from rudderlabs/nisshar/VariadicFunctions

Support for variadic functions

Author: nishantsharma

_examples/variadic/test.py

@@ -0,0 +1,26 @@
+# Copyright 2018 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.
+import variadic, go
+
+############### Non Variadic ##############
+nonvarResult = variadic.NonVariFunc(1, go.Slice_int([2,3,4]),5)
+print("NonVariadic 1+[2+3+4]+5 = %d" % nonvarResult)
+
+############### Variadic Over Int ##############
+varResult = variadic.VariFunc(1,2,3,4,5)
+print("Variadic 1+2+3+4+5 = %d" % varResult)
+
+############### Variadic Over Struct ##############
+varStructResult = variadic.VariStructFunc(variadic.NewIntStrUct(1), variadic.NewIntStrUct(2), variadic.NewIntStrUct(3))
+print("Variadic Struct s(1)+s(2)+s(3) = %d" % varStructResult)
+
+############### Variadic Over InterFace ##############
+varInterFaceResult = variadic.VariInterFaceFunc(variadic.NewIntStrUct(1), variadic.NewIntStrUct(2), variadic.NewIntStrUct(3))
+print("Variadic InterFace i(1)+i(2)+i(3) = %d" % varInterFaceResult)
+
+############### Final ##############
+if isinstance(varResult, int):
+	print("Type OK")
+else:
+	print("Type Not OK")

_examples/variadic/variadic.go

@@ -0,0 +1,57 @@
+package variadic
+
+/////////////// Non Variadic //////////////
+func NonVariFunc(arg1 int, arg2 []int, arg3 int) int{
+	total := arg1
+	for _, num := range arg2 {
+		total += num
+	}
+	total += arg3
+
+	return total
+}
+
+/////////////// Variadic Over Int //////////////
+func VariFunc(vargs ...int) int{
+	total := 0
+	for _, num := range vargs {
+		total += num
+	}
+	return total
+}
+
+/////////////// Variadic Over Struct //////////////
+type IntStrUct struct {
+	p int
+}
+
+func NewIntStrUct(n int) IntStrUct {
+	return IntStrUct {
+		p:n,
+	}
+} 
+
+func VariStructFunc(vargs ...IntStrUct) int{
+	total := 0
+	for _, inst := range vargs {
+		total += inst.p 
+	}
+	return total
+}
+
+/////////////// Variadic Over Interface //////////////
+type IntInterFace interface {
+	Number() int
+}
+
+func (is *IntStrUct) Number() int {
+	return is.p
+}
+
+func VariInterFaceFunc(vargs ...IntInterFace) int{
+	total := 0
+	for _, inst := range vargs {
+		total += inst.Number()
+	}
+	return total
+}

bind/gen_func.go

@@ -87,6 +87,7 @@ func (g *pyGen) genFuncSig(sym *symbol, fsym *Func) bool {
 			return false
 		}
 		anm := pySafeArg(arg.Name(), i)
+
 		if ifchandle && arg.sym.goname == "interface{}" {
 			goArgs = append(goArgs, fmt.Sprintf("%s %s", anm, CGoHandle))
 			pyArgs = append(pyArgs, fmt.Sprintf("param('%s', '%s')", PyHandle, anm))
@@ -98,7 +99,10 @@ func (g *pyGen) genFuncSig(sym *symbol, fsym *Func) bool {
 				pyArgs = append(pyArgs, fmt.Sprintf("param('%s', '%s')", sarg.cpyname, anm))
 			}
 		}
-		wpArgs = append(wpArgs, anm)
+
+		if i!=nargs-1 || !fsym.isVariadic {
+			wpArgs = append(wpArgs, anm)
+		}
 	}
 
 	// support for optional arg to run in a separate go routine -- only if no return val
@@ -108,6 +112,11 @@ func (g *pyGen) genFuncSig(sym *symbol, fsym *Func) bool {
 		wpArgs = append(wpArgs, "goRun=False")
 	}
 
+	// To support variadic args, we add *args at the end.
+	if fsym.isVariadic {
+		wpArgs = append(wpArgs, "*args")
+	}
+
 	// When building the pybindgen builder code, we start with
 	// a function that adds function calls with exception checking.
 	// But given specific return types, we may want to add more
@@ -276,25 +285,6 @@ if __err != nil {
 		g.gofile.Printf("var __err error\n")
 	}
 
-	// pywrap output
-	mnm := fsym.ID()
-	if isMethod {
-		mnm = sym.id + "_" + fsym.GoName()
-	}
-	rvHasHandle := false
-	if nres > 0 {
-		ret := res[0]
-		if !rvIsErr && ret.sym.hasHandle() {
-			rvHasHandle = true
-			cvnm := ret.sym.pyPkgId(g.pkg.pkg)
-			g.pywrap.Printf("return %s(handle=_%s.%s(", cvnm, pkgname, mnm)
-		} else {
-			g.pywrap.Printf("return _%s.%s(", pkgname, mnm)
-		}
-	} else {
-		g.pywrap.Printf("_%s.%s(", pkgname, mnm)
-	}
-
 	callArgs := []string{}
 	wrapArgs := []string{}
 	if isMethod {
@@ -313,6 +303,9 @@ if __err != nil {
 		default:
 			na = anm
 		}
+		if i == len(args) - 1 && fsym.isVariadic {
+			na = na + "..."
+		}
 		callArgs = append(callArgs, na)
 		switch {
 		case arg.sym.goname == "interface{}":
@@ -326,6 +319,34 @@ if __err != nil {
 		default:
 			wrapArgs = append(wrapArgs, anm)
 		}
+
+		// To support variadic args, we add *args at the end.
+		if fsym.isVariadic && i == len(args)-1 {
+			packagePrefix := ""
+			if arg.sym.gopkg.Name() != fsym.pkg.Name() {
+				packagePrefix = arg.sym.gopkg.Name() + "."
+			}
+			g.pywrap.Printf("%s = %s%s(args)\n", anm, packagePrefix, arg.sym.id)
+		}
+	}
+
+	// pywrap output
+	mnm := fsym.ID()
+	if isMethod {
+		mnm = sym.id + "_" + fsym.GoName()
+	}
+	rvHasHandle := false
+	if nres > 0 {
+		ret := res[0]
+		if !rvIsErr && ret.sym.hasHandle() {
+			rvHasHandle = true
+			cvnm := ret.sym.pyPkgId(g.pkg.pkg)
+			g.pywrap.Printf("return %s(handle=_%s.%s(", cvnm, pkgname, mnm)
+		} else {
+			g.pywrap.Printf("return _%s.%s(", pkgname, mnm)
+		}
+	} else {
+		g.pywrap.Printf("_%s.%s(", pkgname, mnm)
 	}
 
 	hasRetCvt := false

bind/symbols.go

@@ -153,11 +153,6 @@ func isPyCompatField(f *types.Var) (*symbol, error) {
 func isPyCompatFunc(sig *types.Signature) (ret types.Type, haserr, hasfun bool, err error) {
 	res := sig.Results()
 
-	if sig.Variadic() {
-		err = fmt.Errorf("gopy: not yet supporting variadic functions: %s", sig.String())
-		return
-	}
-
 	switch res.Len() {
 	case 2:
 		if !isErrorType(res.At(1).Type()) {

bind/types.go

@@ -367,12 +367,13 @@ type Func struct {
 	obj  types.Object
 	name string
 
-	id     string
-	doc    string
-	ret    types.Type // return type, if any
-	err    bool       // true if original go func has comma-error
-	ctor   bool       // true if this is a newXXX function
-	hasfun bool       // true if this function has a function argument
+	id         string
+	doc        string
+	ret        types.Type // return type, if any
+	err        bool       // true if original go func has comma-error
+	ctor       bool       // true if this is a newXXX function
+	hasfun     bool       // true if this function has a function argument
+	isVariadic bool       // True, if this is a variadic function.
 }
 
 func newFuncFrom(p *Package, parent string, obj types.Object, sig *types.Signature) (*Func, error) {
@@ -392,16 +393,17 @@ func newFuncFrom(p *Package, parent string, obj types.Object, sig *types.Signatu
 	}
 
 	return &Func{
-		obj:    obj,
-		pkg:    p,
-		sig:    sv,
-		typ:    obj.Type(),
-		name:   obj.Name(),
-		id:     id,
-		doc:    p.getDoc(parent, obj),
-		ret:    ret,
-		err:    haserr,
-		hasfun: hasfun,
+		obj:        obj,
+		pkg:        p,
+		sig:        sv,
+		typ:        obj.Type(),
+		name:       obj.Name(),
+		id:         id,
+		doc:        p.getDoc(parent, obj),
+		ret:        ret,
+		err:        haserr,
+		hasfun:     hasfun,
+		isVariadic: sig.Variadic(),
 	}, nil
 
 	// TODO: could optimize by generating code once for each type of callback

main_test.go

@@ -48,6 +48,7 @@ var (
 		"_examples/gopygc":      []string{"py2", "py3"},
 		"_examples/cstrings":    []string{"py2", "py3"},
 		"_examples/pkgconflict": []string{"py2", "py3"},
+		"_examples/variadic":    []string{"py3"},
 	}
 
 	testEnvironment = os.Environ()
@@ -811,6 +812,23 @@ func TestPkgConflict(t *testing.T) {
 // 	})
 // }
 
+func TestBindVariadic(t *testing.T) {
+	// t.Parallel()
+	path := "_examples/variadic"
+	testPkg(t, pkg{
+		path:   path,
+		lang:   features[path],
+		cmd:    "build",
+		extras: nil,
+		want: []byte(`NonVariadic 1+[2+3+4]+5 = 15
+Variadic 1+2+3+4+5 = 15
+Variadic Struct s(1)+s(2)+s(3) = 6
+Variadic InterFace i(1)+i(2)+i(3) = 6
+Type OK
+`),
+	})
+}
+
 // Generate / verify SUPPORT_MATRIX.md from features map.
 func TestCheckSupportMatrix(t *testing.T) {
 	var buf bytes.Buffer