wire: only apply wireinject build tag to generated package (google/go-cloud#176)

internal/wire/testdata/BuildTagsMainOnly/bar/bar.go

@@ -0,0 +1,23 @@
+// 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 bar includes both wireinject and non-wireinject variants.
+package bar
+
+import "github.com/google/go-cloud/wire"
+
+// Set provides a friendly user greeting.
+var Set = wire.NewSet(wire.Value("Hello, World!"))

internal/wire/testdata/BuildTagsMainOnly/bar/bar_inject.go

@@ -0,0 +1,22 @@
+// 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 bar
+
+import "github.com/google/go-cloud/wire"
+
+// Set provides an unfriendly user greeting.
+var Set = wire.NewSet(wire.Value("Bah humbug! This is the wrong variant!"))

internal/wire/testdata/BuildTagsMainOnly/foo/foo.go

@@ -0,0 +1,21 @@
+// 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"
+
+func main() {
+	fmt.Println(injectedMessage())
+}

internal/wire/testdata/BuildTagsMainOnly/foo/wire.go

@@ -0,0 +1,28 @@
+// 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 (
+	"bar"
+
+	"github.com/google/go-cloud/wire"
+)
+
+func injectedMessage() string {
+	wire.Build(bar.Set)
+	return ""
+}

internal/wire/testdata/BuildTagsMainOnly/out.txt

@@ -0,0 +1 @@
+Hello, World!

internal/wire/testdata/BuildTagsMainOnly/pkg

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

internal/wire/wire.go

@@ -45,16 +45,26 @@ func Generate(bctx *build.Context, wd string, pkg string) ([]byte, []error) {
 	}
 	// TODO(light): Stop errors from printing to stderr.
 	conf := &loader.Config{
-		Build: new(build.Context),
+		Build: bctx,
 		Cwd:   wd,
 		TypeCheckFuncBodies: func(path string) bool {
 			return path == mainPkg.ImportPath
 		},
+		FindPackage: func(bctx *build.Context, importPath, fromDir string, mode build.ImportMode) (*build.Package, error) {
+			if importPath == mainPkg.ImportPath {
+				// Load in the generated package with the wireinject build tag
+				// to pick up the injector template. The imported packages
+				// should be imported as normal. Since the *build.Context is
+				// shared between calls to FindPackage, this uses a copy.
+				bctx2 := new(build.Context)
+				*bctx2 = *bctx
+				n := len(bctx2.BuildTags)
+				bctx2.BuildTags = append(bctx2.BuildTags[:n:n], "wireinject")
+				bctx = bctx2
+			}
+			return bctx.Import(importPath, fromDir, mode)
+		},
 	}
-	*conf.Build = *bctx
-	n := len(conf.Build.BuildTags)
-	// TODO(light): Only apply wireinject build tag on main package.
-	conf.Build.BuildTags = append(conf.Build.BuildTags[:n:n], "wireinject")
 	conf.Import(pkg)
 
 	prog, err := conf.Load()