VS: Fix '-T version=14.28' under VS 16.9

CMake accepts the toolset version that is default in the current VS
version by matching the name later VS versions will use for the SxS
props files.  It predicts the future name based on the first two
components of the current VS version's default toolset.  However, this
heuristic breaks naming the VS 16.8 toolset version 14.28 under VS 16.9
because the latter's default toolset version is 14.28.29910, which did
not increment the second version component (unprecedented in VS).

Fix this by always using the requested version's SxS props file when it
exists, even if it matches the first two components of the current VS
version's default toolset.  Also add a special case for the name VS
16.10 will use for VS 16.9's default toolset, so that it can be used
with VS 16.9 too.

Fixes: #21922

6 files changed, 108 insertions, 91 deletions

diff --git a/Help/variable/CMAKE_VS_PLATFORM_TOOLSET_VERSION.rst b/Help/variable/CMAKE_VS_PLATFORM_TOOLSET_VERSION.rst
index 64f2e39cbd..b058278fbb 100644
--- a/Help/variable/CMAKE_VS_PLATFORM_TOOLSET_VERSION.rst
+++ b/Help/variable/CMAKE_VS_PLATFORM_TOOLSET_VERSION.rst
@@ -11,3 +11,11 @@ may be specified by a field in :variable:`CMAKE_GENERATOR_TOOLSET` of
 the form ``version=14.11``. If none is specified CMake will choose a default
 toolset. The value may be empty if no minor version was selected and the
 default is used.
+
+If the value is not empty, it is the version number that MSBuild uses in
+its ``Microsoft.VCToolsVersion.*.props`` file names.
+
+.. versionadded:: 3.19.7
+
+   VS 16.9's toolset may also be specified as ``14.28.16.9`` because
+   VS 16.10 uses the file name ``Microsoft.VCToolsVersion.14.28.16.9.props``.
diff --git a/Source/cmGlobalVisualStudio10Generator.cxx b/Source/cmGlobalVisualStudio10Generator.cxx
index 7011333b28..badce2eb52 100644
--- a/Source/cmGlobalVisualStudio10Generator.cxx
+++ b/Source/cmGlobalVisualStudio10Generator.cxx
@@ -3,6 +3,7 @@
 #include "cmGlobalVisualStudio10Generator.h"
 
 #include <algorithm>
+#include <utility>
 
 #include <cm/memory>
 
@@ -329,15 +330,20 @@ bool cmGlobalVisualStudio10Generator::SetGeneratorToolset(
       this->GeneratorToolsetVersion.clear();
     }
 
-    bool const isDefaultToolset =
-      this->IsDefaultToolset(this->GeneratorToolsetVersion);
-    if (isDefaultToolset) {
-      // If the given version is the default toolset, remove the setting
-      this->GeneratorToolsetVersion.clear();
-    } else {
-      std::string const toolsetPath = this->GetAuxiliaryToolset();
-      if (!toolsetPath.empty() && !cmSystemTools::FileExists(toolsetPath)) {
-
+    std::string auxProps;
+    switch (this->FindAuxToolset(this->GeneratorToolsetVersion, auxProps)) {
+      case AuxToolset::None:
+        this->GeneratorToolsetVersionProps = {};
+        break;
+      case AuxToolset::Default:
+        // The given version is the default toolset.  Remove the setting.
+        this->GeneratorToolsetVersion.clear();
+        this->GeneratorToolsetVersionProps = {};
+        break;
+      case AuxToolset::PropsExist:
+        this->GeneratorToolsetVersionProps = std::move(auxProps);
+        break;
+      case AuxToolset::PropsMissing: {
         std::ostringstream e;
         /* clang-format off */
         e <<
@@ -347,22 +353,24 @@ bool cmGlobalVisualStudio10Generator::SetGeneratorToolset(
           "  " << this->GetPlatformToolsetString() << ",version=" <<
           this->GeneratorToolsetVersion << "\n"
           "does not seem to be installed at\n" <<
-          "  " << toolsetPath;
+          "  " << auxProps;
         ;
         /* clang-format on */
         mf->IssueMessage(MessageType::FATAL_ERROR, e.str());
 
         // Clear the configured tool-set
         this->GeneratorToolsetVersion.clear();
-      }
+        this->GeneratorToolsetVersionProps = {};
+      } break;
     }
   }
 
   if (const char* toolset = this->GetPlatformToolset()) {
     mf->AddDefinition("CMAKE_VS_PLATFORM_TOOLSET", toolset);
   }
-  if (const char* version = this->GetPlatformToolsetVersion()) {
-    mf->AddDefinition("CMAKE_VS_PLATFORM_TOOLSET_VERSION", version);
+  if (!this->GeneratorToolsetVersion.empty()) {
+    mf->AddDefinition("CMAKE_VS_PLATFORM_TOOLSET_VERSION",
+                      this->GeneratorToolsetVersion);
   }
   if (const char* hostArch = this->GetPlatformToolsetHostArchitecture()) {
     mf->AddDefinition("CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE", hostArch);
@@ -719,23 +727,10 @@ std::string const& cmGlobalVisualStudio10Generator::GetPlatformToolsetString()
   return empty;
 }
 
-const char* cmGlobalVisualStudio10Generator::GetPlatformToolsetVersion() const
-{
-  std::string const& version = this->GetPlatformToolsetVersionString();
-  if (version.empty()) {
-    return nullptr;
-  }
-  return version.c_str();
-}
-
 std::string const&
-cmGlobalVisualStudio10Generator::GetPlatformToolsetVersionString() const
+cmGlobalVisualStudio10Generator::GetPlatformToolsetVersionProps() const
 {
-  if (!this->GeneratorToolsetVersion.empty()) {
-    return this->GeneratorToolsetVersion;
-  }
-  static std::string const empty;
-  return empty;
+  return this->GeneratorToolsetVersionProps;
 }
 
 const char*
@@ -792,15 +787,11 @@ cmGlobalVisualStudio10Generator::GetPlatformToolsetCudaCustomDirString() const
   return this->GeneratorToolsetCudaCustomDir;
 }
 
-bool cmGlobalVisualStudio10Generator::IsDefaultToolset(
-  const std::string&) const
-{
-  return true;
-}
-
-std::string cmGlobalVisualStudio10Generator::GetAuxiliaryToolset() const
+cmGlobalVisualStudio10Generator::AuxToolset
+cmGlobalVisualStudio10Generator::FindAuxToolset(std::string&,
+                                                std::string&) const
 {
-  return {};
+  return AuxToolset::None;
 }
 
 bool cmGlobalVisualStudio10Generator::FindMakeProgram(cmMakefile* mf)
diff --git a/Source/cmGlobalVisualStudio10Generator.h b/Source/cmGlobalVisualStudio10Generator.h
index 65ea33fc9d..8d30ef8e85 100644
--- a/Source/cmGlobalVisualStudio10Generator.h
+++ b/Source/cmGlobalVisualStudio10Generator.h
@@ -61,9 +61,8 @@ public:
   const char* GetPlatformToolset() const;
   std::string const& GetPlatformToolsetString() const;
 
-  /** The toolset version.  */
-  const char* GetPlatformToolsetVersion() const;
-  std::string const& GetPlatformToolsetVersionString() const;
+  /** The toolset version props file, if any.  */
+  std::string const& GetPlatformToolsetVersionProps() const;
 
   /** The toolset host architecture name (e.g. x64 for 64-bit host tools).  */
   const char* GetPlatformToolsetHostArchitecture() const;
@@ -120,9 +119,6 @@ public:
   std::string Encoding() override;
   const char* GetToolsVersion() const;
 
-  virtual bool IsDefaultToolset(const std::string& version) const;
-  virtual std::string GetAuxiliaryToolset() const;
-
   bool GetSupportsUnityBuilds() const { return this->SupportsUnityBuilds; }
 
   bool FindMakeProgram(cmMakefile* mf) override;
@@ -168,6 +164,16 @@ protected:
   virtual bool SelectWindowsPhoneToolset(std::string& toolset) const;
   virtual bool SelectWindowsStoreToolset(std::string& toolset) const;
 
+  enum class AuxToolset
+  {
+    None,
+    Default,
+    PropsExist,
+    PropsMissing
+  };
+  virtual AuxToolset FindAuxToolset(std::string& version,
+                                    std::string& props) const;
+
   std::string const& GetMSBuildCommand();
 
   cmIDEFlagTable const* LoadFlagTable(std::string const& optionsName,
@@ -176,7 +182,7 @@ protected:
                                       std::string const& table) const;
 
   std::string GeneratorToolset;
-  std::string GeneratorToolsetVersion;
+  std::string GeneratorToolsetVersionProps;
   std::string GeneratorToolsetHostArchitecture;
   std::string GeneratorToolsetCustomVCTargetsDir;
   std::string GeneratorToolsetCuda;
@@ -230,6 +236,8 @@ private:
   std::string FindDevEnvCommand() override;
   std::string GetVSMakeProgram() override { return this->GetMSBuildCommand(); }
 
+  std::string GeneratorToolsetVersion;
+
   bool PlatformToolsetNeedsDebugEnum;
 
   bool ParseGeneratorToolset(std::string const& ts, cmMakefile* mf);
diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.cxx b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
index 84f870ea6d..4e2464b2c8 100644
--- a/Source/cmGlobalVisualStudioVersionedGenerator.cxx
+++ b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
@@ -2,6 +2,8 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmGlobalVisualStudioVersionedGenerator.h"
 
+#include <cmext/string_view>
+
 #include "cmAlgorithms.h"
 #include "cmDocumentationEntry.h"
 #include "cmLocalVisualStudio10Generator.h"
@@ -391,27 +393,6 @@ bool cmGlobalVisualStudioVersionedGenerator::GetVSInstanceVersion(
   return vsSetupAPIHelper.GetVSInstanceVersion(vsInstanceVersion);
 }
 
-bool cmGlobalVisualStudioVersionedGenerator::IsDefaultToolset(
-  const std::string& version) const
-{
-  if (version.empty()) {
-    return true;
-  }
-
-  std::string vcToolsetVersion;
-  if (this->vsSetupAPIHelper.GetVCToolsetVersion(vcToolsetVersion)) {
-
-    cmsys::RegularExpression regex("[0-9][0-9]\\.[0-9]+");
-    if (regex.find(version) && regex.find(vcToolsetVersion)) {
-      const auto majorMinorEnd = vcToolsetVersion.find('.', 3);
-      const auto majorMinor = vcToolsetVersion.substr(0, majorMinorEnd);
-      return version == majorMinor;
-    }
-  }
-
-  return false;
-}
-
 bool cmGlobalVisualStudioVersionedGenerator::IsStdOutEncodingSupported() const
 {
   // Supported from Visual Studio 16.7 Preview 3.
@@ -446,29 +427,58 @@ cmGlobalVisualStudioVersionedGenerator::GetAndroidApplicationTypeRevision()
   return "";
 }
 
-std::string cmGlobalVisualStudioVersionedGenerator::GetAuxiliaryToolset() const
+cmGlobalVisualStudioVersionedGenerator::AuxToolset
+cmGlobalVisualStudioVersionedGenerator::FindAuxToolset(
+  std::string& version, std::string& props) const
 {
-  const char* version = this->GetPlatformToolsetVersion();
-  if (version) {
-    std::string instancePath;
-    GetVSInstance(instancePath);
-    std::string toolsetDir = instancePath + "/VC/Auxiliary/Build";
-    char sep = '/';
-    if (cmSystemTools::VersionCompareGreaterEq(version, "14.20")) {
-      std::string toolsetDot =
-        cmStrCat(toolsetDir, '.', version, "/Microsoft.VCToolsVersion.",
-                 version, ".props");
-      if (cmSystemTools::PathExists(toolsetDot)) {
-        sep = '.';
+  if (version.empty()) {
+    return AuxToolset::None;
+  }
+
+  std::string instancePath;
+  this->GetVSInstance(instancePath);
+  cmSystemTools::ConvertToUnixSlashes(instancePath);
+
+  if (cmSystemTools::VersionCompareGreaterEq(version, "14.20")) {
+    props = cmStrCat(instancePath, "/VC/Auxiliary/Build."_s, version,
+                     "/Microsoft.VCToolsVersion."_s, version, ".props"_s);
+    if (cmSystemTools::PathExists(props)) {
+      return AuxToolset::PropsExist;
+    }
+  }
+  props = cmStrCat(instancePath, "/VC/Auxiliary/Build/"_s, version,
+                   "/Microsoft.VCToolsVersion."_s, version, ".props"_s);
+  if (cmSystemTools::PathExists(props)) {
+    return AuxToolset::PropsExist;
+  }
+
+  // Accept the toolset version that is default in the current VS version
+  // by matching the name later VS versions will use for the SxS props files.
+  std::string vcToolsetVersion;
+  if (this->vsSetupAPIHelper.GetVCToolsetVersion(vcToolsetVersion)) {
+    // Accept an exact-match (three-component version).
+    if (version == vcToolsetVersion) {
+      return AuxToolset::Default;
+    }
+
+    // Accept known SxS props file names using four version components
+    // in VS versions later than the current.
+    if (version == "14.28.16.9" && vcToolsetVersion == "14.28.29910") {
+      return AuxToolset::Default;
+    }
+
+    // The first two components of the default toolset version typically
+    // match the name used by later VS versions for the SxS props files.
+    cmsys::RegularExpression twoComponent("^([0-9]+\\.[0-9]+)");
+    if (twoComponent.find(version)) {
+      std::string const versionPrefix = cmStrCat(twoComponent.match(1), '.');
+      if (cmHasPrefix(vcToolsetVersion, versionPrefix)) {
+        return AuxToolset::Default;
       }
     }
-    std::string toolsetPath =
-      cmStrCat(toolsetDir, sep, version, "/Microsoft.VCToolsVersion.", version,
-               ".props");
-    cmSystemTools::ConvertToUnixSlashes(toolsetPath);
-    return toolsetPath;
   }
-  return {};
+
+  return AuxToolset::PropsMissing;
 }
 
 bool cmGlobalVisualStudioVersionedGenerator::InitializeWindows(cmMakefile* mf)
diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.h b/Source/cmGlobalVisualStudioVersionedGenerator.h
index 46a5f40e53..cee129e52b 100644
--- a/Source/cmGlobalVisualStudioVersionedGenerator.h
+++ b/Source/cmGlobalVisualStudioVersionedGenerator.h
@@ -30,8 +30,8 @@ public:
 
   bool GetVSInstanceVersion(unsigned long long& vsInstanceVersion) const;
 
-  bool IsDefaultToolset(const std::string& version) const override;
-  std::string GetAuxiliaryToolset() const override;
+  AuxToolset FindAuxToolset(std::string& version,
+                            std::string& props) const override;
 
   bool IsStdOutEncodingSupported() const override;
 
diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index 4eb3b7f8fc..489e42d8e4 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -623,14 +623,14 @@ void cmVisualStudio10TargetGenerator::Generate()
     }
 
     switch (this->ProjectType) {
-      case vcxproj:
-        if (this->GlobalGenerator->GetPlatformToolsetVersion()) {
-          Elem(e0, "Import")
-            .Attribute("Project",
-                       this->GlobalGenerator->GetAuxiliaryToolset());
+      case vcxproj: {
+        std::string const& props =
+          this->GlobalGenerator->GetPlatformToolsetVersionProps();
+        if (!props.empty()) {
+          Elem(e0, "Import").Attribute("Project", props);
         }
         Elem(e0, "Import").Attribute("Project", VS10_CXX_DEFAULT_PROPS);
-        break;
+      } break;
       case csproj:
         Elem(e0, "Import")
           .Attribute("Project", VS10_CSharp_DEFAULT_PROPS)