Nullable annotate System.Diagnostics.Process (dotnet#31671)

* nullable annotate System.Diagnostics.Process

* add annotations to unix source files

* annotate remainder of non-windows implementations

* enable nullable annotation for file

* add nullable directive to cgroups.cs

* add missing nullable directives in shared files

* enable nullable annotations for ReusableTextReader

* add missing #nullable enable directives in shared files

* address feedback

* address feedback

* ensure ComputerName property is non-nullable

* assert non-nullability for specific Process.Start() overloads

src/libraries/Common/src/Interop/FreeBSD/Interop.Process.cs

@@ -256,7 +256,7 @@ internal static unsafe int[] ListAllPids()
         /// Gets executable name for process given it's PID
         /// </summary>
         /// <param name="pid">The PID of the process</param>
-        public static unsafe string GetProcPath(int pid)
+        public static unsafe string? GetProcPath(int pid)
         {
             Span<int> sysctlName = stackalloc int[4];
             byte* pBuffer = null;
@@ -359,7 +359,7 @@ public static unsafe ProcessInfo GetProcessInfoById(int pid)
                 // Get the process information for the specified pid
                 info = new ProcessInfo();
 
-                info.ProcessName = Marshal.PtrToStringAnsi((IntPtr)kinfo->ki_comm);
+                info.ProcessName = Marshal.PtrToStringAnsi((IntPtr)kinfo->ki_comm)!;
                 info.BasePriority = kinfo->ki_nice;
                 info.VirtualBytes = (long)kinfo->ki_size;
                 info.WorkingSet = kinfo->ki_rssize;

src/libraries/Common/src/Interop/Linux/cgroups/Interop.cgroups.cs

@@ -2,9 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System;
 using System.Buffers.Text;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 
 internal static partial class Interop
@@ -24,14 +26,14 @@ internal enum CGroupVersion { None, CGroup1, CGroup2 };
         private const string ProcCGroupFilePath = "/proc/self/cgroup";
 
         /// <summary>Path to the found cgroup memory limit path, or null if it couldn't be found.</summary>
-        internal static readonly string s_cgroupMemoryLimitPath = FindCGroupMemoryLimitPath();
+        internal static readonly string? s_cgroupMemoryLimitPath = FindCGroupMemoryLimitPath();
 
         /// <summary>Tries to read the memory limit from the cgroup memory location.</summary>
         /// <param name="limit">The read limit, or 0 if it couldn't be read.</param>
         /// <returns>true if the limit was read successfully; otherwise, false.</returns>
         public static bool TryGetMemoryLimit(out ulong limit)
         {
-            string path = s_cgroupMemoryLimitPath;
+            string? path = s_cgroupMemoryLimitPath;
 
             if (path != null &&
                 TryReadMemoryValueFromFile(path, out limit))
@@ -102,9 +104,9 @@ internal static bool TryReadMemoryValueFromFile(string path, out ulong result)
 
         /// <summary>Find the cgroup memory limit path.</summary>
         /// <returns>The limit path if found; otherwise, null.</returns>
-        private static string FindCGroupMemoryLimitPath()
+        private static string? FindCGroupMemoryLimitPath()
         {
-            string cgroupMemoryPath = FindCGroupPath("memory", out CGroupVersion version);
+            string? cgroupMemoryPath = FindCGroupPath("memory", out CGroupVersion version);
             if (cgroupMemoryPath != null)
             {
                 if (version == CGroupVersion.CGroup1)
@@ -126,10 +128,10 @@ private static string FindCGroupMemoryLimitPath()
         /// <summary>Find the cgroup path for the specified subsystem.</summary>
         /// <param name="subsystem">The subsystem, e.g. "memory".</param>
         /// <returns>The cgroup path if found; otherwise, null.</returns>
-        private static string FindCGroupPath(string subsystem, out CGroupVersion version)
+        private static string? FindCGroupPath(string subsystem, out CGroupVersion version)
         {
-            if (TryFindHierarchyMount(subsystem, out version, out string hierarchyRoot, out string hierarchyMount) &&
-                TryFindCGroupPathForSubsystem(subsystem, out string cgroupPathRelativeToMount))
+            if (TryFindHierarchyMount(subsystem, out version, out string? hierarchyRoot, out string? hierarchyMount) &&
+                TryFindCGroupPathForSubsystem(subsystem, out string? cgroupPathRelativeToMount))
             {
                 // For a host cgroup, we need to append the relative path.
                 // In a docker container, the root and relative path are the same and we don't need to append.
@@ -146,20 +148,20 @@ private static string FindCGroupPath(string subsystem, out CGroupVersion version
         /// <param name="root">The path of the directory in the filesystem which forms the root of this mount; null if not found.</param>
         /// <param name="path">The path of the mount point relative to the process's root directory; null if not found.</param>
         /// <returns>true if the mount was found; otherwise, null.</returns>
-        private static bool TryFindHierarchyMount(string subsystem, out CGroupVersion version, out string root, out string path)
+        private static bool TryFindHierarchyMount(string subsystem, out CGroupVersion version, [NotNullWhen(true)] out string? root, [NotNullWhen(true)] out string? path)
         {
             return TryFindHierarchyMount(ProcMountInfoFilePath, subsystem, out version, out root, out path);
         }
 
-        internal static bool TryFindHierarchyMount(string mountInfoFilePath, string subsystem, out CGroupVersion version, out string root, out string path)
+        internal static bool TryFindHierarchyMount(string mountInfoFilePath, string subsystem, out CGroupVersion version, [NotNullWhen(true)] out string? root, [NotNullWhen(true)] out string? path)
         {
             if (File.Exists(mountInfoFilePath))
             {
                 try
                 {
                     using (var reader = new StreamReader(mountInfoFilePath))
                     {
-                        string line;
+                        string? line;
                         while ((line = reader.ReadLine()) != null)
                         {
                             // Look for an entry that has cgroup as the "filesystem type"
@@ -235,20 +237,20 @@ internal static bool TryFindHierarchyMount(string mountInfoFilePath, string subs
         /// <param name="subsystem">The subsystem, e.g. "memory".</param>
         /// <param name="path">The found path, or null if it couldn't be found.</param>
         /// <returns></returns>
-        private static bool TryFindCGroupPathForSubsystem(string subsystem, out string path)
+        private static bool TryFindCGroupPathForSubsystem(string subsystem, [NotNullWhen(true)] out string? path)
         {
             return TryFindCGroupPathForSubsystem(ProcCGroupFilePath, subsystem, out path);
         }
 
-        internal static bool TryFindCGroupPathForSubsystem(string procCGroupFilePath, string subsystem, out string path)
+        internal static bool TryFindCGroupPathForSubsystem(string procCGroupFilePath, string subsystem, [NotNullWhen(true)] out string? path)
         {
             if (File.Exists(procCGroupFilePath))
             {
                 try
                 {
                     using (var reader = new StreamReader(procCGroupFilePath))
                     {
-                        string line;
+                        string? line;
                         while ((line = reader.ReadLine()) != null)
                         {
                             string[] lineParts = line.Split(':');

src/libraries/Common/src/Interop/Linux/procfs/Interop.ProcFsStat.cs

@@ -2,9 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Text;
@@ -243,7 +245,7 @@ internal static bool TryReadStatusFile(int pid, out ParsedStatus result, Reusabl
 
         internal static bool TryParseStatFile(string statFilePath, out ParsedStat result, ReusableTextReader reusableReader)
         {
-            if (!TryReadFile(statFilePath, reusableReader, out string statFileContents))
+            if (!TryReadFile(statFilePath, reusableReader, out string? statFileContents))
             {
                 // Between the time that we get an ID and the time that we try to read the associated stat
                 // file(s), the process could be gone.
@@ -312,7 +314,7 @@ internal static bool TryParseStatFile(string statFilePath, out ParsedStat result
 
         internal static bool TryParseStatusFile(string statusFilePath, out ParsedStatus result, ReusableTextReader reusableReader)
         {
-            if (!TryReadFile(statusFilePath, reusableReader, out string fileContents))
+            if (!TryReadFile(statusFilePath, reusableReader, out string? fileContents))
             {
                 // Between the time that we get an ID and the time that we try to read the associated stat
                 // file(s), the process could be gone.
@@ -415,7 +417,7 @@ internal static bool TryParseStatusFile(string statusFilePath, out ParsedStatus
             return true;
         }
 
-        private static bool TryReadFile(string filePath, ReusableTextReader reusableReader, out string fileContents)
+        private static bool TryReadFile(string filePath, ReusableTextReader reusableReader, [NotNullWhen(true)] out string? fileContents)
         {
             try
             {

src/libraries/Common/src/Interop/OSX/Interop.libproc.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
@@ -362,7 +364,7 @@ private static extern unsafe int proc_pidinfo(
 
             int result = 0;
             int size = 20; // start assuming 20 threads is enough
-            ulong[] threadIds = null;
+            ulong[]? threadIds = null;
             var threads = new List<KeyValuePair<ulong, proc_threadinfo?>>();
 
             // We have no way of knowing how many threads the process has (and therefore how big our buffer should be)

src/libraries/Common/src/Interop/Unix/System.Native/Interop.ForkAndExecProcess.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.ComponentModel;
 using System.Diagnostics;
@@ -13,9 +15,9 @@ internal static partial class Interop
     internal static partial class Sys
     {
         internal static unsafe int ForkAndExecProcess(
-            string filename, string[] argv, string[] envp, string cwd,
+            string filename, string[] argv, string[] envp, string? cwd,
             bool redirectStdin, bool redirectStdout, bool redirectStderr,
-            bool setUser, uint userId, uint groupId, uint[] groups,
+            bool setUser, uint userId, uint groupId, uint[]? groups,
             out int lpChildPid, out int stdinFd, out int stdoutFd, out int stderrFd, bool shouldThrow = true)
         {
             byte** argvPtr = null, envpPtr = null;
@@ -43,7 +45,7 @@ internal static unsafe int ForkAndExecProcess(
 
         [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ForkAndExecProcess", SetLastError = true)]
         private static extern unsafe int ForkAndExecProcess(
-            string filename, byte** argv, byte** envp, string cwd,
+            string filename, byte** argv, byte** envp, string? cwd,
             int redirectStdin, int redirectStdout, int redirectStderr,
             int setUser, uint userId, uint groupId, uint* groups, int groupsLength,
             out int lpChildPid, out int stdinFd, out int stdoutFd, out int stderrFd);

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetGroupList.cs

@@ -2,14 +2,16 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
 {
     internal static partial class Sys
     {
-        internal static unsafe uint[] GetGroupList(string userName, uint primaryGroupId)
+        internal static unsafe uint[]? GetGroupList(string userName, uint primaryGroupId)
         {
             const int InitialGroupsLength =
 #if DEBUG

src/libraries/Common/src/Interop/Windows/Advapi32/Interop.CreateProcessWithLogon.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Runtime.InteropServices;
 using System.Text;
@@ -16,7 +18,7 @@ internal static extern bool CreateProcessWithLogonW(
             string domain,
             IntPtr password,
             LogonFlags logonFlags,
-            string appName,
+            string? appName,
             [In] StringBuilder cmdLine,
             int creationFlags,
             IntPtr environmentBlock,

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.CreateProcess.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using Microsoft.Win32.SafeHandles;
 using System;
 using System.Runtime.InteropServices;
@@ -13,7 +15,7 @@ internal partial class Kernel32
     {
         [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, BestFitMapping = false, EntryPoint = "CreateProcessW")]
         internal static extern bool CreateProcess(
-            string lpApplicationName,
+            string? lpApplicationName,
             [In] StringBuilder lpCommandLine,
             ref SECURITY_ATTRIBUTES procSecAttrs,
             ref SECURITY_ATTRIBUTES threadSecAttrs,

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.ProcessWaitHandle.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using Microsoft.Win32.SafeHandles;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -14,7 +15,7 @@ internal sealed class ProcessWaitHandle : WaitHandle
         {
             internal ProcessWaitHandle(SafeProcessHandle processHandle)
             {
-                SafeWaitHandle waitHandle = null;
+                SafeWaitHandle? waitHandle;
                 SafeProcessHandle currentProcHandle = Interop.Kernel32.GetCurrentProcess();
                 bool succeeded = Interop.Kernel32.DuplicateHandle(
                     currentProcHandle,

src/libraries/Common/src/System/Runtime/Serialization/SerializationGuard.cs

@@ -12,16 +12,16 @@ namespace System.Runtime.Serialization
     internal static partial class SerializationGuard
     {
         private delegate void ThrowIfDeserializationInProgressWithSwitchDel(string switchName, ref int cachedValue);
-        private static readonly ThrowIfDeserializationInProgressWithSwitchDel s_throwIfDeserializationInProgressWithSwitch = CreateThrowIfDeserializationInProgressWithSwitchDelegate();
+        private static readonly ThrowIfDeserializationInProgressWithSwitchDel? s_throwIfDeserializationInProgressWithSwitch = CreateThrowIfDeserializationInProgressWithSwitchDelegate();
 
         /// <summary>
         /// Builds a wrapper delegate for SerializationInfo.ThrowIfDeserializationInProgress(string, ref int),
         /// since it is not exposed via contracts.
         /// </summary>
-        private static ThrowIfDeserializationInProgressWithSwitchDel CreateThrowIfDeserializationInProgressWithSwitchDelegate()
+        private static ThrowIfDeserializationInProgressWithSwitchDel? CreateThrowIfDeserializationInProgressWithSwitchDelegate()
         {
-            ThrowIfDeserializationInProgressWithSwitchDel throwIfDeserializationInProgressDelegate = null;
-            MethodInfo throwMethod = typeof(SerializationInfo).GetMethod("ThrowIfDeserializationInProgress",
+            ThrowIfDeserializationInProgressWithSwitchDel? throwIfDeserializationInProgressDelegate = null;
+            MethodInfo? throwMethod = typeof(SerializationInfo).GetMethod("ThrowIfDeserializationInProgress",
                 BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public, null, new Type[] { typeof(string), typeof(int).MakeByRefType() }, Array.Empty<ParameterModifier>());
 
             if (throwMethod != null)

src/libraries/Common/src/System/Text/ReusableTextReader.cs

@@ -4,6 +4,8 @@
 
 using System.IO;
 
+#nullable enable
+
 namespace System.Text
 {
     /// <summary>Provides a reusable reader for reading all of the text from streams.</summary>
@@ -21,7 +23,7 @@ internal sealed class ReusableTextReader
         /// <summary>Initializes a new reusable reader.</summary>
         /// <param name="encoding">The Encoding to use.  Defaults to UTF8.</param>
         /// <param name="bufferSize">The size of the buffer to use when reading from the stream.</param>
-        public ReusableTextReader(Encoding encoding = null, int bufferSize = 1024)
+        public ReusableTextReader(Encoding? encoding = null, int bufferSize = 1024)
         {
             if (encoding == null)
             {