Don't try to download a new distribution if the name is already in use (#13046)

Author: OneBlue

src/windows/common/WslInstall.cpp

@@ -271,6 +271,15 @@ std::pair<std::wstring, GUID> WslInstall::InstallModernDistribution(
     const std::optional<uint64_t>& vhdSize,
     const bool fixedVhd)
 {
+    wsl::windows::common::SvcComm service;
+
+    // Fail early if the distributions name is already in use.
+    auto result = wil::ResultFromException([&]() {
+        service.GetDistributionId(name.has_value() ? name->c_str() : distribution.Name.c_str(), LXSS_GET_DISTRO_ID_LIST_ALL);
+    });
+
+    THROW_HR_IF(HRESULT_FROM_WIN32(ERROR_ALREADY_EXISTS), SUCCEEDED(result));
+    LOG_HR_IF(result, result != WSL_E_DISTRO_NOT_FOUND);
 
     const auto downloadInfo = wsl::shared::Arm64 ? distribution.Arm64Url : distribution.Amd64Url;
     THROW_HR_IF(E_UNEXPECTED, !downloadInfo.has_value());
@@ -304,7 +313,6 @@ std::pair<std::wstring, GUID> WslInstall::InstallModernDistribution(
 
     wsl::windows::common::HandleConsoleProgressBar progressBar(file.get(), Localization::MessageImportProgress());
 
-    wsl::windows::common::SvcComm service;
     auto [id, installedName] = service.RegisterDistribution(
         name.has_value() ? name->c_str() : distribution.Name.c_str(),
         version.value_or(LXSS_WSL_VERSION_DEFAULT),

test/windows/UnitTests.cpp

@@ -5085,6 +5085,58 @@ Error code: Wsl/InstallDistro/WSL_E_DISTRO_NOT_FOUND\r\n",
                 L"");
         }
 
+        // Validate that a distribution isn't downloaded if its name is already in use.
+        {
+            auto manifest = std::format(
+                R"({{
+    "ModernDistributions": {{
+        "debian": [
+            {{
+                "Name": "{}",
+                "FriendlyName": "DebianFriendlyName",
+                "Amd64Url": {{
+                    "Url": "file://doesnotexist",
+                    "Sha256": ""
+                }}
+            }},
+            {{
+                "Name": "dummy",
+                "FriendlyName": "dummy",
+                "Amd64Url": {{
+                    "Url": "file://doesnotexist",
+                    "Sha256": ""
+                }}
+            }}
+        ]
+    }}
+}})",
+                LXSS_DISTRO_NAME_TEST);
+
+            auto restore = SetManifest(manifest);
+
+            {
+                auto [out, err] = LxsstuLaunchWslAndCaptureOutput(std::format(L"--install {}", LXSS_DISTRO_NAME_TEST_L), -1);
+
+                VERIFY_ARE_EQUAL(
+                    out,
+                    L"A distribution with the supplied name already exists. Use --name to chose a different name.\r\n"
+                    L"Error code: Wsl/InstallDistro/ERROR_ALREADY_EXISTS\r\n");
+
+                VERIFY_ARE_EQUAL(err, L"");
+            }
+
+            {
+                auto [out, err] = LxsstuLaunchWslAndCaptureOutput(std::format(L"--install dummy --name {}", LXSS_DISTRO_NAME_TEST_L), -1);
+
+                VERIFY_ARE_EQUAL(
+                    out,
+                    L"A distribution with the supplied name already exists. Use --name to chose a different name.\r\n"
+                    L"Error code: Wsl/InstallDistro/ERROR_ALREADY_EXISTS\r\n");
+
+                VERIFY_ARE_EQUAL(err, L"");
+            }
+        }
+
         // Validate handling of case where no default install distro is configured.
         {
             auto manifest =