feat: support method expression providers

Author: cmilesio

internal/wire/analyze.go

@@ -52,6 +52,10 @@ type call struct {
 	pkg  *types.Package
 	name string
 
+	// methodExprRecv is the receiver type for a method expression provider.
+	// It is nil for package-level function providers.
+	methodExprRecv types.Type
+
 	// args is a list of arguments to call the provider with. Each element is:
 	// a) one of the givens (args[i] < len(given)),
 	// b) the result of a previous provider call (args[i] >= len(given))
@@ -196,16 +200,17 @@ dfs:
 				}
 			}
 			calls = append(calls, call{
-				kind:       kind,
-				pkg:        p.Pkg,
-				name:       p.Name,
-				args:       args,
-				varargs:    p.Varargs,
-				fieldNames: fieldNames,
-				ins:        ins,
-				out:        curr.t,
-				hasCleanup: p.HasCleanup,
-				hasErr:     p.HasErr,
+				kind:           kind,
+				pkg:            p.Pkg,
+				name:           p.Name,
+				methodExprRecv: p.MethodExprRecv,
+				args:           args,
+				varargs:        p.Varargs,
+				fieldNames:     fieldNames,
+				ins:            ins,
+				out:            curr.t,
+				hasCleanup:     p.HasCleanup,
+				hasErr:         p.HasErr,
 			})
 		case pv.IsValue():
 			v := pv.Value()

internal/wire/parse.go

@@ -156,6 +156,10 @@ type Provider struct {
 	// Name is the name of the Go object.
 	Name string
 
+	// MethodExprRecv is the receiver type for a method expression provider.
+	// It is nil for package-level function providers.
+	MethodExprRecv types.Type
+
 	// Pos is the source position of the func keyword or type spec
 	// defining this provider.
 	Pos token.Pos
@@ -718,6 +722,12 @@ func valueSpecForVar(fset *token.FileSet, files []*ast.File, obj *types.Var) *as
 func (oc *objectCache) processExpr(info *types.Info, pkgPath string, expr ast.Expr, varName string) (interface{}, []error) {
 	exprPos := oc.fset.Position(expr.Pos())
 	expr = astutil.Unparen(expr)
+	if sel, ok := expr.(*ast.SelectorExpr); ok {
+		if selInfo := info.Selections[sel]; selInfo != nil && selInfo.Kind() == types.MethodExpr {
+			p, errs := processMethodExprProvider(oc.fset, info, sel, selInfo)
+			return p, notePositionAll(exprPos, errs)
+		}
+	}
 	if obj := qualifiedIdentObject(info, expr); obj != nil {
 		item, errs := oc.get(obj)
 		return item, mapErrors(errs, func(err error) error {
@@ -877,28 +887,45 @@ func qualifiedIdentObject(info *types.Info, expr ast.Expr) types.Object {
 func processFuncProvider(fset *token.FileSet, fn *types.Func) (*Provider, []error) {
 	sig := fn.Type().(*types.Signature)
 	fpos := fn.Pos()
+	return processProviderSignature(fset, fn.Pkg(), fn.Name(), nil, fpos, sig)
+}
+
+func processMethodExprProvider(fset *token.FileSet, info *types.Info, expr *ast.SelectorExpr, sel *types.Selection) (*Provider, []error) {
+	obj, ok := sel.Obj().(*types.Func)
+	if !ok {
+		return nil, []error{fmt.Errorf("%s is not a function", expr.Sel.Name)}
+	}
+	sig, ok := info.TypeOf(expr).(*types.Signature)
+	if !ok {
+		return nil, []error{fmt.Errorf("method expression %s does not have a function signature", expr.Sel.Name)}
+	}
+	return processProviderSignature(fset, obj.Pkg(), obj.Name(), sel.Recv(), expr.Pos(), sig)
+}
+
+func processProviderSignature(fset *token.FileSet, pkg *types.Package, name string, recv types.Type, pos token.Pos, sig *types.Signature) (*Provider, []error) {
 	providerSig, err := funcOutput(sig)
 	if err != nil {
-		return nil, []error{notePosition(fset.Position(fpos), fmt.Errorf("wrong signature for provider %s: %v", fn.Name(), err))}
+		return nil, []error{notePosition(fset.Position(pos), fmt.Errorf("wrong signature for provider %s: %v", name, err))}
 	}
 	params := sig.Params()
 	provider := &Provider{
-		Pkg:        fn.Pkg(),
-		Name:       fn.Name(),
-		Pos:        fn.Pos(),
-		Args:       make([]ProviderInput, params.Len()),
-		Varargs:    sig.Variadic(),
-		Out:        []types.Type{providerSig.out},
-		HasCleanup: providerSig.cleanup,
-		HasErr:     providerSig.err,
+		Pkg:            pkg,
+		Name:           name,
+		MethodExprRecv: recv,
+		Pos:            pos,
+		Args:           make([]ProviderInput, params.Len()),
+		Varargs:        sig.Variadic(),
+		Out:            []types.Type{providerSig.out},
+		HasCleanup:     providerSig.cleanup,
+		HasErr:         providerSig.err,
 	}
 	for i := 0; i < params.Len(); i++ {
 		provider.Args[i] = ProviderInput{
 			Type: params.At(i).Type(),
 		}
 		for j := 0; j < i; j++ {
 			if types.Identical(provider.Args[i].Type, provider.Args[j].Type) {
-				return nil, []error{notePosition(fset.Position(fpos), fmt.Errorf("provider has multiple parameters of type %s", types.TypeString(provider.Args[j].Type, nil)))}
+				return nil, []error{notePosition(fset.Position(pos), fmt.Errorf("provider has multiple parameters of type %s", types.TypeString(provider.Args[j].Type, nil)))}
 			}
 		}
 	}

internal/wire/testdata/MethodExprProvider/foo/foo.go

@@ -0,0 +1,41 @@
+// Copyright 2018 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import "fmt"
+
+func main() {
+	db, err := initDB()
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(db.DSN)
+}
+
+type Options struct {
+	DSN string
+}
+
+type DB struct {
+	DSN string
+}
+
+func provideOptions() *Options {
+	return &Options{DSN: "postgres://wire"}
+}
+
+func (o *Options) ToDB() (*DB, error) {
+	return &DB{DSN: o.DSN}, nil
+}

internal/wire/testdata/MethodExprProvider/foo/wire.go

@@ -0,0 +1,28 @@
+// Copyright 2018 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build wireinject
+// +build wireinject
+
+package main
+
+import "github.com/goforj/wire"
+
+func initDB() (*DB, error) {
+	wire.Build(
+		provideOptions,
+		(*Options).ToDB,
+	)
+	return nil, nil
+}

internal/wire/testdata/MethodExprProvider/pkg

@@ -0,0 +1 @@
+example.com/foo

internal/wire/testdata/MethodExprProvider/want/program_out.txt

@@ -0,0 +1 @@
+postgres://wire

internal/wire/testdata/MethodExprProvider/want/wire_gen.go

@@ -720,7 +720,7 @@ func (ig *injectorGen) funcProviderCall(lname string, c *call, injectSig outputS
 		ig.p(", %s", ig.errVar)
 	}
 	ig.p(" := ")
-	ig.p("%s(", ig.g.qualifiedID(c.pkg.Name(), c.pkg.Path(), c.name))
+	ig.p("%s(", ig.funcProviderExpr(c))
 	for i, a := range c.args {
 		if i > 0 {
 			ig.p(", ")
@@ -750,6 +750,17 @@ func (ig *injectorGen) funcProviderCall(lname string, c *call, injectSig outputS
 	}
 }
 
+func (ig *injectorGen) funcProviderExpr(c *call) string {
+	if c.methodExprRecv == nil {
+		return ig.g.qualifiedID(c.pkg.Name(), c.pkg.Path(), c.name)
+	}
+	recv := types.TypeString(c.methodExprRecv, ig.g.qualifyPkg)
+	if _, ok := c.methodExprRecv.(*types.Pointer); ok {
+		recv = "(" + recv + ")"
+	}
+	return recv + "." + c.name
+}
+
 func (ig *injectorGen) structProviderCall(lname string, c *call) {
 	ig.p("\t%s", lname)
 	ig.p(" := ")