oraios/serena · error · SolidLSPException

Failed to download package {package_name} version {package_v

Error message

Failed to download package {package_name} version {package_version} from NuGet.org: {e}

What it means

Raised by _download_nuget_package when the actual download/extraction of the Roslyn NuGet package from NuGet.org throws; the original exception is wrapped in a SolidLSPException with the package name/version. It signals network or extraction failure against the direct NuGet.org endpoint.

Source

Thrown at src/solidlsp/language_servers/csharp_language_server.py:487

                log.warning("Using a short temporary directory for Roslyn package extraction because the configured cache path is too deep")
                package_extract_dir = Path(tempfile.mkdtemp(prefix="serena-roslyn-")) / package_extract_dir.name
            package_extract_dir.parent.mkdir(parents=True, exist_ok=True)

            try:
                log.debug(f"Downloading package from: {url}")
                FileUtils.download_and_extract_archive_verified(
                    url,
                    str(package_extract_dir),
                    "zip",
                    expected_sha256=dependency.sha256,
                    allowed_hosts=dependency.allowed_hosts,
                )

                log.info(f"Successfully downloaded and extracted {package_name} version {package_version} from NuGet.org")
                return package_extract_dir

            except Exception as e:
                raise SolidLSPException(f"Failed to download package {package_name} version {package_version} from NuGet.org: {e}") from e

    def _create_base_initialize_params(self) -> dict:
        """
        Returns the initialize params for the Microsoft.CodeAnalysis.LanguageServer.
        """
        return {
            "capabilities": {
                "window": {
                    "workDoneProgress": True,
                    "showMessage": {"messageActionItem": {"additionalPropertiesSupport": True}},
                    "showDocument": {"support": True},
                },
                "workspace": {
                    "applyEdit": True,
                    "workspaceEdit": {"documentChanges": True},
                    "didChangeConfiguration": {"dynamicRegistration": True},
                    "didChangeWatchedFiles": {"dynamicRegistration": True},
                    "symbol": {

View on GitHub (pinned to 7fcbca7e62)

Solutions

Check network access to https://www.nuget.org (curl the package URL manually) and configure proxy env vars (HTTPS_PROXY) if needed
Verify the package name/version exists on NuGet.org and retry — transient 5xx/rate-limit failures may pass on retry
Free disk space / ensure the temp download dir is writable
If NuGet.org is blocked, supply a reachable mirror URL in the dependency entry

Example fix

// before
$ curl -I https://www.nuget.org/api/v2/package/microsoft.codeanalysis.languageserver/4.x  # 403 (proxy)
// after
export HTTPS_PROXY=http://proxy.corp:8080
# then rerun setup

Defensive patterns

Strategy: retry

Validate before calling

import urllib.request
url = f"https://www.nuget.org/api/v2/package/{dep.package_name}/{dep.package_version}"
try:
    urllib.request.urlopen(url, timeout=15)
    print("NuGet.org reachable")
except Exception as e:
    print(f"NuGet.org unreachable, fix network/proxy first: {e}")

Type guard

def nuget_reachable(timeout: float = 15) -> bool:
    import urllib.request
    try:
        urllib.request.urlopen("https://www.nuget.org/", timeout=timeout)
        return True
    except OSError:
        return False

Try / catch

import time
for attempt in range(3):
    try:
        ls._ensure_server_installed()
        break
    except SolidLSPException as e:
        if "Failed to download package" in str(e) and attempt < 2:
            time.sleep(2 ** attempt)
            continue
        raise

Prevention

Configure HTTPS_PROXY/HTTP_PROXY in environments behind corporate proxies
Retry transient NuGet failures with exponential backoff
Free adequate disk space before large package downloads
Pin package versions that exist on NuGet.org to avoid 404s

When it happens

Trigger: _ensure_language_server -> _download_nuget_package when the HTTP request to NuGet.org fails (connection error, timeout, 404/403) or archive extraction raises, for any of the calling contexts including the listed tests.

Common situations: Corporate proxies/firewalls blocking nuget.org, DNS failures, NuGet.org rate limiting or temporary outages, insufficient disk space during extraction, or the package/version URL returning 404.

Related errors

AI-assisted analysis of oraios/serena@7fcbca7e62 (2026-08-29). Data as JSON: /api/errors/83b6fe44f1e62c8e. Report an issue: GitHub.