wire: Build now returns an error if it has any unused arguments (google/go-cloud#268)

Fixes google/go-cloud#164

internal/wire/analyze.go

@@ -108,7 +108,6 @@ func solve(fset *token.FileSet, out types.Type, given []types.Type, set *Provide
 			index.Set(g, i)
 		}
 	}
-
 	if len(ec.errors) > 0 {
 		return nil, ec.errors
 	}
@@ -118,6 +117,7 @@ func solve(fset *token.FileSet, out types.Type, given []types.Type, set *Provide
 	// guaranteed to be acyclic. An index value of errAbort indicates that
 	// the type was visited, but failed due to an error added to ec.
 	errAbort := errors.New("failed to visit")
+	var used []*providerSetSrc
 	var calls []call
 	type frame struct {
 		t    types.Type
@@ -145,6 +145,8 @@ dfs:
 			continue
 		case pv.IsProvider():
 			p := pv.Provider()
+			src := set.srcMap.At(curr.t).(*providerSetSrc)
+			used = append(used, src)
 			if !types.Identical(p.Out, curr.t) {
 				// Interface binding.  Don't create a call ourselves.
 				i := index.At(p.Out)
@@ -212,6 +214,8 @@ dfs:
 				index.Set(curr.t, i)
 				continue
 			}
+			src := set.srcMap.At(curr.t).(*providerSetSrc)
+			used = append(used, src)
 			index.Set(curr.t, len(given)+len(calls))
 			calls = append(calls, call{
 				kind:          valueExpr,
@@ -226,14 +230,77 @@ dfs:
 	if len(ec.errors) > 0 {
 		return nil, ec.errors
 	}
+	if errs := verifyArgsUsed(set, used); len(errs) > 0 {
+		return nil, errs
+	}
 	return calls, nil
 }
 
-// buildProviderMap creates the providerMap field for a given provider set.
-// The given provider set's providerMap field is ignored.
-func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *ProviderSet) (*typeutil.Map, []error) {
+// verifyArgsUsed ensures that all of the arguments in set were used during solve.
+func verifyArgsUsed(set *ProviderSet, used []*providerSetSrc) []error {
+	var errs []error
+	for _, imp := range set.Imports {
+		found := false
+		for _, u := range used {
+			if u.Import == imp {
+				found = true
+				break
+			}
+		}
+		if !found {
+			if imp.Name == "" {
+				errs = append(errs, errors.New("unused provider set"))
+			} else {
+				errs = append(errs, fmt.Errorf("unused provider set %q", imp.Name))
+			}
+		}
+	}
+	for _, p := range set.Providers {
+		found := false
+		for _, u := range used {
+			if u.Provider == p {
+				found = true
+				break
+			}
+		}
+		if !found {
+			errs = append(errs, fmt.Errorf("unused provider %q", p.Name))
+		}
+	}
+	for _, v := range set.Values {
+		found := false
+		for _, u := range used {
+			if u.Value == v {
+				found = true
+				break
+			}
+		}
+		if !found {
+			errs = append(errs, fmt.Errorf("unused value of type %s", types.TypeString(v.Out, nil)))
+		}
+	}
+	for _, b := range set.Bindings {
+		found := false
+		for _, u := range used {
+			if u.Binding == b {
+				found = true
+				break
+			}
+		}
+		if !found {
+			errs = append(errs, fmt.Errorf("unused interface binding to type %s", types.TypeString(b.Iface, nil)))
+		}
+	}
+	return errs
+}
+
+// buildProviderMap creates the providerMap and srcMap fields for a given provider set.
+// The given provider set's providerMap and srcMap fields are ignored.
+func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *ProviderSet) (*typeutil.Map, *typeutil.Map, []error) {
 	providerMap := new(typeutil.Map)
 	providerMap.SetHasher(hasher)
+	srcMap := new(typeutil.Map)
+	srcMap.SetHasher(hasher)
 	setMap := new(typeutil.Map) // to *ProviderSet, for error messages
 	setMap.SetHasher(hasher)
 
@@ -246,11 +313,12 @@ func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *Provider
 				return
 			}
 			providerMap.Set(k, v)
+			srcMap.Set(k, &providerSetSrc{Import: imp})
 			setMap.Set(k, imp)
 		})
 	}
 	if len(ec.errors) > 0 {
-		return nil, ec.errors
+		return nil, nil, ec.errors
 	}
 
 	// Process non-binding providers in new set.
@@ -260,6 +328,7 @@ func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *Provider
 			continue
 		}
 		providerMap.Set(p.Out, p)
+		srcMap.Set(p.Out, &providerSetSrc{Provider: p})
 		setMap.Set(p.Out, set)
 	}
 	for _, v := range set.Values {
@@ -268,10 +337,11 @@ func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *Provider
 			continue
 		}
 		providerMap.Set(v.Out, v)
+		srcMap.Set(v.Out, &providerSetSrc{Value: v})
 		setMap.Set(v.Out, set)
 	}
 	if len(ec.errors) > 0 {
-		return nil, ec.errors
+		return nil, nil, ec.errors
 	}
 
 	// Process bindings in set. Must happen after the other providers to
@@ -289,12 +359,13 @@ func buildProviderMap(fset *token.FileSet, hasher typeutil.Hasher, set *Provider
 			continue
 		}
 		providerMap.Set(b.Iface, concrete)
+		srcMap.Set(b.Iface, &providerSetSrc{Binding: b})
 		setMap.Set(b.Iface, set)
 	}
 	if len(ec.errors) > 0 {
-		return nil, ec.errors
+		return nil, nil, ec.errors
 	}
-	return providerMap, nil
+	return providerMap, srcMap, nil
 }
 
 func verifyAcyclic(providerMap *typeutil.Map, hasher typeutil.Hasher) []error {

internal/wire/parse.go

@@ -29,6 +29,15 @@ import (
 	"golang.org/x/tools/go/types/typeutil"
 )
 
+// A providerSetSrc captures the source for a type provided by a ProviderSet.
+// Exactly one of the fields will be set.
+type providerSetSrc struct {
+	Provider *Provider
+	Binding  *IfaceBinding
+	Value    *Value
+	Import   *ProviderSet
+}
+
 // A ProviderSet describes a set of providers.  The zero value is an empty
 // ProviderSet.
 type ProviderSet struct {
@@ -49,6 +58,10 @@ type ProviderSet struct {
 	// providerMap maps from provided type to a *Provider or *Value.
 	// It includes all of the imported types.
 	providerMap *typeutil.Map
+
+	// srcMap maps from provided type to a *providerSetSrc capturing the
+	// Provider, Binding, Value, or Import that provided the type.
+	srcMap *typeutil.Map
 }
 
 // Outputs returns a new slice containing the set of possible types the
@@ -496,7 +509,7 @@ func (oc *objectCache) processNewSet(pkg *loader.PackageInfo, call *ast.CallExpr
 		return nil, ec.errors
 	}
 	var errs []error
-	pset.providerMap, errs = buildProviderMap(oc.prog.Fset, oc.hasher, pset)
+	pset.providerMap, pset.srcMap, errs = buildProviderMap(oc.prog.Fset, oc.hasher, pset)
 	if len(errs) > 0 {
 		return nil, errs
 	}

internal/wire/testdata/UnusedProviders/foo/foo.go

@@ -0,0 +1,71 @@
+// Copyright 2018 Google LLC
+//
+// 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"
+
+	"github.com/google/go-cloud/wire"
+)
+
+func main() {
+	fmt.Println(injectBar())
+}
+
+type Foo int
+type Bar int
+type Unused int
+type UnusedInSet int
+type OneOfTwo int
+type TwoOfTwo int
+
+var (
+	unusedSet        = wire.NewSet(provideUnusedInSet)
+	partiallyUsedSet = wire.NewSet(provideOneOfTwo, provideTwoOfTwo)
+)
+
+type Fooer interface {
+	Foo() string
+}
+
+func (f *Foo) Foo() string {
+	return fmt.Sprintf("Hello World %d", f)
+}
+
+func provideFoo() *Foo {
+	f := new(Foo)
+	*f = 1
+	return f
+}
+
+func provideBar(foo *Foo, one OneOfTwo) Bar {
+	return Bar(int(*foo) + int(one))
+}
+
+func provideUnused() Unused {
+	return 1
+}
+
+func provideUnusedInSet() UnusedInSet {
+	return 1
+}
+
+func provideOneOfTwo() OneOfTwo {
+	return 1
+}
+
+func provideTwoOfTwo() TwoOfTwo {
+	return 1
+}

internal/wire/testdata/UnusedProviders/foo/wire.go

@@ -0,0 +1,34 @@
+// Copyright 2018 Google LLC
+//
+// 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.
+
+//+build wireinject
+
+package main
+
+import (
+	"github.com/google/go-cloud/wire"
+)
+
+func injectBar() Bar {
+	wire.Build(
+		provideFoo,                            // needed as input for provideBar
+		provideBar,                            // needed for Bar
+		partiallyUsedSet,                      // 1/2 providers in the set are needed
+		provideUnused,                         // not needed -> error
+		wire.Value("unused"),                  // not needed -> error
+		unusedSet,                             // nothing in set is needed -> error
+		wire.Bind((*Fooer)(nil), (*Foo)(nil)), // binding to Fooer is not needed -> error
+	)
+	return 0
+}

internal/wire/testdata/UnusedProviders/out.txt

@@ -0,0 +1,5 @@
+ERROR
+unused provider set
+unused provider "provideUnused"
+unused value of type string
+unused interface binding to type foo.Fooer

internal/wire/testdata/UnusedProviders/pkg

@@ -0,0 +1 @@
+foo