wire: change call sites to allow multiple errors (google/go-cloud#118)

Updated the call sites to allow multiple errors to be returned from
the package. Load is now permitted to return partial success.

Updates google/go-cloud#5

internal/wire/parse.go

@@ -144,8 +144,9 @@ type Value struct {
 }
 
 // Load finds all the provider sets in the given packages, as well as
-// the provider sets' transitive dependencies.
-func Load(bctx *build.Context, wd string, pkgs []string) (*Info, error) {
+// the provider sets' transitive dependencies. It may return both an error
+// and Info.
+func Load(bctx *build.Context, wd string, pkgs []string) (*Info, []error) {
 	// TODO(light): Stop errors from printing to stderr.
 	conf := &loader.Config{
 		Build:               bctx,
@@ -157,7 +158,7 @@ func Load(bctx *build.Context, wd string, pkgs []string) (*Info, error) {
 	}
 	prog, err := conf.Load()
 	if err != nil {
-		return nil, fmt.Errorf("load: %v", err)
+		return nil, []error{fmt.Errorf("load: %v", err)}
 	}
 	info := &Info{
 		Fset: prog.Fset,

internal/wire/wire.go

@@ -38,10 +38,10 @@ import (
 
 // Generate performs dependency injection for a single package,
 // returning the gofmt'd Go source code.
-func Generate(bctx *build.Context, wd string, pkg string) ([]byte, error) {
+func Generate(bctx *build.Context, wd string, pkg string) ([]byte, []error) {
 	mainPkg, err := bctx.Import(pkg, wd, build.FindOnly)
 	if err != nil {
-		return nil, fmt.Errorf("load: %v", err)
+		return nil, []error{fmt.Errorf("load: %v", err)}
 	}
 	// TODO(light): Stop errors from printing to stderr.
 	conf := &loader.Config{
@@ -59,17 +59,17 @@ func Generate(bctx *build.Context, wd string, pkg string) ([]byte, error) {
 
 	prog, err := conf.Load()
 	if err != nil {
-		return nil, fmt.Errorf("load: %v", err)
+		return nil, []error{fmt.Errorf("load: %v", err)}
 	}
 	if len(prog.InitialPackages()) != 1 {
 		// This is more of a violated precondition than anything else.
-		return nil, fmt.Errorf("load: got %d packages", len(prog.InitialPackages()))
+		return nil, []error{fmt.Errorf("load: got %d packages", len(prog.InitialPackages()))}
 	}
 	pkgInfo := prog.InitialPackages()[0]
 	g := newGen(prog, pkgInfo.Pkg.Path())
 	injectorFiles, err := generateInjectors(g, pkgInfo)
 	if err != nil {
-		return nil, err
+		return nil, []error{err}
 	}
 	copyNonInjectorDecls(g, injectorFiles, &pkgInfo.Info)
 	goSrc := g.frame()
@@ -77,7 +77,7 @@ func Generate(bctx *build.Context, wd string, pkg string) ([]byte, error) {
 	if err != nil {
 		// This is likely a bug from a poorly generated source file.
 		// Return an error and the unformatted source.
-		return goSrc, err
+		return goSrc, []error{err}
 	}
 	return fmtSrc, nil
 }

internal/wire/wire_test.go

@@ -69,17 +69,17 @@ func TestWire(t *testing.T) {
 		for _, test := range tests {
 			t.Run(test.name, func(t *testing.T) {
 				bctx := test.buildContext()
-				gen, err := Generate(bctx, wd, test.pkg)
+				gen, errs := Generate(bctx, wd, test.pkg)
 				if len(gen) > 0 {
 					defer t.Logf("wire_gen.go:\n%s", gen)
 				}
-				if err != nil {
+				if len(errs) > 0 {
 					if !test.wantError {
-						t.Fatalf("wirego: %v", err)
+						t.Fatalf("wirego: %v", errs)
 					}
 					return
 				}
-				if err == nil && test.wantError {
+				if len(errs) == 0 && test.wantError {
 					t.Fatal("wirego succeeded; want error")
 				}
 
@@ -133,15 +133,15 @@ func TestWire(t *testing.T) {
 			}
 			t.Run(test.name, func(t *testing.T) {
 				bctx := test.buildContext()
-				gold, err := Generate(bctx, wd, test.pkg)
-				if err != nil {
-					t.Fatal("wirego:", err)
+				gold, errs := Generate(bctx, wd, test.pkg)
+				if len(errs) > 0 {
+					t.Fatal("wirego:", errs)
 				}
 				goldstr := string(gold)
 				for i := 0; i < runs-1; i++ {
-					out, err := Generate(bctx, wd, test.pkg)
-					if err != nil {
-						t.Fatal("wirego (on subsequent run):", err)
+					out, errs := Generate(bctx, wd, test.pkg)
+					if len(errs) > 0 {
+						t.Fatal("wirego (on subsequent run):", errs)
 					}
 					if !bytes.Equal(gold, out) {
 						t.Fatalf("wirego output differs when run repeatedly on same input:\n%s", diff(goldstr, string(out)))