C#: Make sure allFeeds contains at least explicitFeeds

csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs

@@ -158,6 +158,10 @@ IEnumerable<string> IBuildActions.EnumerateDirectories(string dir)
 
         bool IBuildActions.IsMacOs() => IsMacOs;
 
+        public bool IsLinux { get; set; }
+
+        bool IBuildActions.IsLinux() => IsLinux;
+
         public bool IsRunningOnAppleSilicon { get; set; }
 
         bool IBuildActions.IsRunningOnAppleSilicon() => IsRunningOnAppleSilicon;

csharp/autobuilder/Semmle.Autobuild.Cpp.Tests/BuildScripts.cs

@@ -146,6 +146,10 @@ IEnumerable<string> IBuildActions.EnumerateDirectories(string dir)
 
         bool IBuildActions.IsMacOs() => IsMacOs;
 
+        public bool IsLinux { get; set; }
+
+        bool IBuildActions.IsLinux() => IsLinux;
+
         public bool IsRunningOnAppleSilicon { get; set; }
 
         bool IBuildActions.IsRunningOnAppleSilicon() => IsRunningOnAppleSilicon;

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/NugetPackageRestorer.cs

@@ -814,6 +814,43 @@ private IEnumerable<string> GetFeeds(Func<IList<string>> getNugetFeeds)
         private (HashSet<string> explicitFeeds, HashSet<string> allFeeds) GetAllFeeds()
         {
             var nugetConfigs = fileProvider.NugetConfigs;
+
+            // On systems with case-sensitive file systems (for simplicity, we assume that is Linux), the
+            // filenames of NuGet configuration files must be named correctly. For compatibility with projects
+            // that are typically built on Windows or macOS where this doesn't matter, we accept all variants
+            // of `nuget.config` ourselves. However, `dotnet` does not. If we detect that incorrectly-named
+            // files are present, we emit a diagnostic to warn the user.
+            if (SystemBuildActions.Instance.IsLinux())
+            {
+                string[] acceptedNugetConfigNames = ["nuget.config", "NuGet.config", "NuGet.Config"];
+                var invalidNugetConfigs = nugetConfigs
+                    .Where(path => !acceptedNugetConfigNames.Contains(Path.GetFileName(path)));
+
+                if (invalidNugetConfigs.Count() > 0)
+                {
+                    this.logger.LogWarning(string.Format(
+                        "Found incorrectly named NuGet configuration files: {0}",
+                        string.Join(", ", invalidNugetConfigs)
+                    ));
+                    this.diagnosticsWriter.AddEntry(new DiagnosticMessage(
+                        Language.CSharp,
+                        "buildless/case-sensitive-nuget-config",
+                        "Found NuGet configuration files which are not correctly named",
+                        visibility: new DiagnosticMessage.TspVisibility(statusPage: true, cliSummaryTable: true, telemetry: true),
+                        markdownMessage: string.Format(
+                            "On platforms with case-sensitive file systems, NuGet only accepts files with one of the following names: {0}.\n\n" +
+                            "CodeQL found the following files while performing an analysis on a platform with a case-sensitive file system:\n\n" +
+                            "{1}\n\n" +
+                            "To avoid unexpected results, rename these files to match the casing of one of the accepted filenames.",
+                            string.Join(", ", acceptedNugetConfigNames),
+                            string.Join("\n", invalidNugetConfigs.Select(path => string.Format("- `{0}`", path)))
+                        ),
+                        severity: DiagnosticMessage.TspSeverity.Warning
+                    ));
+                }
+            }
+
+            // Find feeds that are explicitly configured in the NuGet configuration files that we found.
             var explicitFeeds = nugetConfigs
                 .SelectMany(config => GetFeeds(() => dotnet.GetNugetFeeds(config)))
                 .ToHashSet();
@@ -849,6 +886,17 @@ private IEnumerable<string> GetFeeds(Func<IList<string>> getNugetFeeds)
                     .Where(folder => folder != null)
                     .SelectMany(folder => GetFeeds(() => dotnet.GetNugetFeedsFromFolder(folder!)))
                     .ToHashSet();
+
+                // If we have discovered any explicit feeds, then we also expect these to be in the set of all feeds.
+                // Normally, it is a safe assumption to make that `GetNugetFeedsFromFolder` will include the feeds configured
+                // in a NuGet configuration file in the given directory. There is one exception: on a system with case-sensitive
+                // file systems, we may discover a configuration file such as `Nuget.Config` which is not recognised by `dotnet nuget`.
+                // In that case, our call to `GetNugetFeeds` will retrieve the feeds from that file (because it is accepted when
+                // provided explicitly as `--configfile` argument), but the call to `GetNugetFeedsFromFolder` will not.
+                if (explicitFeeds.Count > 0)
+                {
+                    allFeeds.UnionWith(explicitFeeds);
+                }
             }
             else
             {

csharp/extractor/Semmle.Util/BuildActions.cs

@@ -119,6 +119,12 @@ public interface IBuildActions
         /// <returns>True if we are running on macOS.</returns>
         bool IsMacOs();
 
+        /// <summary>
+        /// Gets a value indicating whether we are running on Linux.
+        /// </summary>
+        /// <returns>True if we are running on Linux.</returns>
+        bool IsLinux();
+
         /// <summary>
         /// Gets a value indicating whether we are running on Apple Silicon.
         /// </summary>
@@ -246,6 +252,8 @@ int IBuildActions.RunProcess(string cmd, string args, string? workingDirectory,
 
         bool IBuildActions.IsMacOs() => RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
 
+        bool IBuildActions.IsLinux() => RuntimeInformation.IsOSPlatform(OSPlatform.Linux);
+
         bool IBuildActions.IsRunningOnAppleSilicon()
         {
             var thisBuildActions = (IBuildActions)this;

csharp/ql/integration-tests/linux/diag_nuget_config_casing/Program.cs

@@ -0,0 +1,6 @@
+class Program
+{
+    static void Main(string[] args)
+    {
+    }
+}

csharp/ql/integration-tests/linux/diag_nuget_config_casing/diagnostics.expected

@@ -0,0 +1,42 @@
+{
+  "markdownMessage": "C# analysis with build-mode 'none' completed.",
+  "severity": "unknown",
+  "source": {
+    "extractorName": "csharp",
+    "id": "csharp/autobuilder/buildless/complete",
+    "name": "C# analysis with build-mode 'none' completed"
+  },
+  "visibility": {
+    "cliSummaryTable": true,
+    "statusPage": false,
+    "telemetry": true
+  }
+}
+{
+  "markdownMessage": "C# was extracted with build-mode set to 'none'. This means that all C# source in the working directory will be scanned, with build tools, such as NuGet and dotnet CLIs, only contributing information about external dependencies.",
+  "severity": "note",
+  "source": {
+    "extractorName": "csharp",
+    "id": "csharp/autobuilder/buildless/mode-active",
+    "name": "C# was extracted with build-mode set to 'none'"
+  },
+  "visibility": {
+    "cliSummaryTable": true,
+    "statusPage": true,
+    "telemetry": true
+  }
+}
+{
+  "markdownMessage": "On platforms with case-sensitive file systems, NuGet only accepts files with one of the following names: nuget.config, NuGet.config, NuGet.Config.\n\nCodeQL found the following files while performing an analysis on a platform with a case-sensitive file system:\n\n- `<test-root-directory>/sub-project/Nuget.Config`\n\nTo avoid unexpected results, rename these files to match the casing of one of the accepted filenames.",
+  "severity": "warning",
+  "source": {
+    "extractorName": "csharp",
+    "id": "csharp/autobuilder/buildless/case-sensitive-nuget-config",
+    "name": "Found NuGet configuration files which are not correctly named"
+  },
+  "visibility": {
+    "cliSummaryTable": true,
+    "statusPage": true,
+    "telemetry": true
+  }
+}

csharp/ql/integration-tests/linux/diag_nuget_config_casing/global.json

@@ -0,0 +1,5 @@
+{
+    "sdk": {
+        "version": "10.0.100"
+    }
+}

csharp/ql/integration-tests/linux/diag_nuget_config_casing/sub-project/Nuget.Config

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+  </packageSources>
+</configuration>

csharp/ql/integration-tests/linux/diag_nuget_config_casing/test.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

csharp/ql/integration-tests/linux/diag_nuget_config_casing/test.py

@@ -0,0 +1,5 @@
+import runs_on
+
+@runs_on.linux
+def test(codeql, csharp):
+    codeql.database.create(build_mode="none")