internal/fetchdatasource: GetUnitMeta returns NotFound on missing package

If a module exists but the package path is not in it, return NotFound.

For golang/go#47780

Change-Id: If3a6602df4b99c8470020e8538e01c685880d86d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/345251
Trust: Jonathan Amsterdam <[email protected]>
Run-TryBot: Jonathan Amsterdam <[email protected]>
TryBot-Result: kokoro <[email protected]>
Reviewed-by: Jamal Carvalho <[email protected]>
Reviewed-by: Julie Qiu <[email protected]>

Author: jba

internal/fetchdatasource/fetchdatasource.go

@@ -181,10 +181,12 @@ func (ds *FetchDataSource) GetUnitMeta(ctx context.Context, path, requestedModul
 		Path:       path,
 		ModuleInfo: module.ModuleInfo,
 	}
-	if u := findUnit(module, path); u != nil {
-		um.Name = u.Name
-		um.IsRedistributable = u.IsRedistributable
+	u := findUnit(module, path)
+	if u == nil {
+		return nil, derrors.NotFound
 	}
+	um.Name = u.Name
+	um.IsRedistributable = u.IsRedistributable
 	return um, nil
 }
 

internal/fetchdatasource/fetchdatasource_test.go

@@ -309,10 +309,9 @@ func TestGetLatestInfo(t *testing.T) {
 			wantErr:    derrors.NotFound,
 		},
 		{
-			fullPath:        "foo.com/bar/baz",
-			modulePath:      "foo.com/bar",
-			wantModulePath:  "foo.com/bar/v3",
-			wantPackagePath: "foo.com/bar/v3",
+			fullPath:   "foo.com/bar/baz",
+			modulePath: "foo.com/bar",
+			wantErr:    derrors.NotFound,
 		},
 		{
 			fullPath:        "incompatible.com/bar",
@@ -424,6 +423,12 @@ func TestLocalGetUnitMeta(t *testing.T) {
 			modulePath: stdlib.ModulePath,
 			wantErr:    derrors.InvalidArgument,
 		},
+		{
+			// Module is known but path isn't in it.
+			path:       "github.com/my/module/unk",
+			modulePath: "github.com/my/module",
+			wantErr:    derrors.NotFound,
+		},
 	} {
 		t.Run(test.path, func(t *testing.T) {
 			got, err := ds.GetUnitMeta(ctx, test.path, test.modulePath, fetch.LocalVersion)