Reject a whitespace-only repository name from a host

GitIntegration.Test/Hosting/AzureDevOpsProviderTests.cs

@@ -166,6 +166,25 @@
 		StringAssert.Contains(exception.Message, "..");
 	}
 
+	[TestMethod]
+	public async Task ThrowsWhenARepositoryNameIsWhitespaceOnlyAsync()
+	{
+		// Path.GetFileName("   ") returns "   " unchanged — there is no separator to strip, so the
+		// leaf is exactly the whitespace-only input. GitRepositoryName itself rejects a
+		// whitespace-only value ([HasNonWhitespaceContent]), so LocalPath is held to the same rule:
+		// a name the semantic type would refuse is not a name this mapping can turn into a directory
+		// either.
+		using FakeHttpMessageHandler handler = new FakeHttpMessageHandler()
+			.Respond(HttpStatusCode.OK, SingleRepositoryResponse("   "), ("Content-Type", "application/json"));
+		AzureDevOpsProvider provider = new() { Owner = "contoso".As<GitProviderOwner>(), Handler = handler };
+
+		GitHostingRequestException exception = await Assert.ThrowsExactlyAsync<GitHostingRequestException>(
+			async () => await provider.GetRepositoriesAsync(TestContext.CancellationTokenSource.Token).ConfigureAwait(false))
+			.ConfigureAwait(false);
+
+		StringAssert.Contains(exception.Message, "cannot be represented as a local directory");
+	}
+
 	[TestMethod]
 	public async Task ThrowsWhenARepositoryNameIsMissingAsync()
 	{

GitIntegration.Test/Hosting/GitHubProviderTests.cs

@@ -168,6 +168,25 @@
 		StringAssert.Contains(exception.Message, "..");
 	}
 
+	[TestMethod]
+	public async Task ThrowsWhenARepositoryNameIsWhitespaceOnlyAsync()
+	{
+		// Path.GetFileName("   ") returns "   " unchanged — there is no separator to strip, so the
+		// leaf is exactly the whitespace-only input. GitRepositoryName itself rejects a
+		// whitespace-only value ([HasNonWhitespaceContent]), so LocalPath is held to the same rule:
+		// a name the semantic type would refuse is not a name this mapping can turn into a directory
+		// either.
+		using FakeHttpMessageHandler handler = new FakeHttpMessageHandler()
+			.Respond(HttpStatusCode.OK, SingleRepositoryArray("   "), ("Content-Type", "application/json"));
+		GitHubProvider provider = new() { Owner = "contoso".As<GitProviderOwner>(), Handler = handler };
+
+		GitHostingRequestException exception = await Assert.ThrowsExactlyAsync<GitHostingRequestException>(
+			async () => await provider.GetRepositoriesAsync(TestContext.CancellationTokenSource.Token).ConfigureAwait(false))
+			.ConfigureAwait(false);
+
+		StringAssert.Contains(exception.Message, "cannot be represented as a local directory");
+	}
+
 	[TestMethod]
 	public async Task MapsAnOpenPullRequestToOpenAsync()
 	{

GitIntegration/GitProvider.cs

@@ -241,14 +241,14 @@ internal HostingCredential ResolveCredential() =>
 	/// derived leaf segment of <paramref name="repositoryName"/>.
 	/// </returns>
 	/// <exception cref="GitHostingRequestException">
-	/// <paramref name="repositoryName"/> is <see langword="null"/>, empty, or a name from which no
-	/// directory segment can be derived.
+	/// <paramref name="repositoryName"/> is <see langword="null"/>, empty, consists only of
+	/// whitespace, or is a name from which no directory segment can otherwise be derived.
 	/// </exception>
 	internal static AbsoluteDirectoryPath ToLocalRepositoryPath(string? repositoryName, GitProviderName providerName)
 	{
 		string leaf = Path.GetFileName(repositoryName ?? string.Empty);
 
-		if (string.IsNullOrEmpty(leaf) || leaf is "." or "..")
+		if (string.IsNullOrWhiteSpace(leaf) || leaf is "." or "..")
 		{
 			throw new GitHostingRequestException(
 				$"{providerName} reported a repository name '{repositoryName}' that cannot be represented as a local directory.");