chore: Fix repo allow forking (#3094)

Signed-off-by: Steve Hipwell <steve.hipwell@gmail.com>

Author: stevehipwell

github/resource_github_repository.go

@@ -634,9 +634,10 @@ func resourceGithubRepositoryObject(d *schema.ResourceData) *github.Repository {
 	}
 
 	// only configure allow forking if repository is not public
-	allowForking, ok := d.Get("allow_forking").(bool)
-	if ok && visibility != "public" {
-		repository.AllowForking = github.Ptr(allowForking)
+	if allowForking, ok := d.GetOk("allow_forking"); ok && visibility != "public" {
+		if val, ok := allowForking.(bool); ok {
+			repository.AllowForking = github.Ptr(val)
+		}
 	}
 
 	return repository

github/resource_github_repository_test.go

@@ -571,7 +571,7 @@ func TestAccGithubRepository(t *testing.T) {
 
 	t.Run("create_private_with_forking", func(t *testing.T) {
 		randomID := acctest.RandStringFromCharSet(5, acctest.CharSetAlphaNum)
-		repoName := fmt.Sprintf("%svisibility-%s", testResourcePrefix, randomID)
+		repoName := fmt.Sprintf("%s%s", testResourcePrefix, randomID)
 
 		config := fmt.Sprintf(`
 		resource "github_repository" "test" {
@@ -597,6 +597,33 @@ func TestAccGithubRepository(t *testing.T) {
 		})
 	})
 
+	t.Run("create_private_with_forking_unset", func(t *testing.T) {
+		randomID := acctest.RandStringFromCharSet(5, acctest.CharSetAlphaNum)
+		repoName := fmt.Sprintf("%s%s", testResourcePrefix, randomID)
+
+		config := fmt.Sprintf(`
+resource "github_repository" "test" {
+	name       = "%s"
+	description = "A private repository with forking disabled"
+	visibility = "private"
+}
+`, repoName)
+
+		resource.Test(t, resource.TestCase{
+			PreCheck:          func() { skipUnlessHasOrgs(t) },
+			ProviderFactories: providerFactories,
+			Steps: []resource.TestStep{
+				{
+					Config: config,
+					Check: resource.ComposeTestCheckFunc(
+						resource.TestCheckResourceAttr("github_repository.test", "visibility", "private"),
+						resource.TestCheckResourceAttr("github_repository.test", "allow_forking", "false"),
+					),
+				},
+			},
+		})
+	})
+
 	t.Run("configures vulnerability alerts for a private repository", func(t *testing.T) {
 		randomID := acctest.RandStringFromCharSet(5, acctest.CharSetAlphaNum)
 		repoName := fmt.Sprintf("%sprv-vuln-%s", testResourcePrefix, randomID)