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

1 files changed, 50 insertions, 40 deletions

diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.cxx b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
index 84f870e..4e2464b 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)