[vcpkg] Adding support for finding VS2019 by environment variable (#10760)

* Fixing build with VS2019

* Added support for finding VS2019 by VS160COMNTOOLS env var

* [vcpkg] Explicitly handle trailing backslash in VS140 path.

* [vcpkg] Defer instance validation for VS160COMNTOOLS

Co-authored-by: Robert Schumacher <roschuma@microsoft.com>

1 files changed, 24 insertions, 6 deletions

diff --git a/toolsrc/src/vcpkg/visualstudio.cpp b/toolsrc/src/vcpkg/visualstudio.cpp
index df3c70de2..44ce4be7d 100644
--- a/toolsrc/src/vcpkg/visualstudio.cpp
+++ b/toolsrc/src/vcpkg/visualstudio.cpp
@@ -119,7 +119,23 @@ namespace vcpkg::VisualStudio
             }
         }
 
-        const auto append_if_has_cl = [&](fs::path&& path_root) {
+        // VS2019 instance from environment variable
+        auto maybe_vs160_comntools = System::get_environment_variable("vs160comntools");
+        if (const auto path_as_string = maybe_vs160_comntools.get())
+        {
+            // We want lexically_normal(), but it is not available
+            // Correct root path might be 2 or 3 levels up, depending on if the path has trailing backslash.
+            auto common7_tools = fs::u8path(*path_as_string);
+            if (common7_tools.filename().empty())
+                instances.emplace_back(common7_tools.parent_path().parent_path().parent_path(),
+                                       "16.0",
+                                       VisualStudioInstance::ReleaseType::LEGACY);
+            else
+                instances.emplace_back(
+                    common7_tools.parent_path().parent_path(), "16.0", VisualStudioInstance::ReleaseType::LEGACY);
+        }
+
+        const auto append_if_has_cl_vs140 = [&](fs::path&& path_root) {
             const auto cl_exe = path_root / "VC" / "bin" / "cl.exe";
             const auto vcvarsall_bat = path_root / "VC" / "vcvarsall.bat";
 
@@ -132,14 +148,16 @@ namespace vcpkg::VisualStudio
         if (const auto path_as_string = maybe_vs140_comntools.get())
         {
             // We want lexically_normal(), but it is not available
-            // Correct root path might be 2 or 3 levels up, depending on if the path has trailing backslash. Try both.
-            auto common7_tools = fs::path{*path_as_string};
-            append_if_has_cl(fs::path{*path_as_string}.parent_path().parent_path());
-            append_if_has_cl(fs::path{*path_as_string}.parent_path().parent_path().parent_path());
+            // Correct root path might be 2 or 3 levels up, depending on if the path has trailing backslash.
+            auto common7_tools = fs::u8path(*path_as_string);
+            if (common7_tools.filename().empty())
+                append_if_has_cl_vs140(common7_tools.parent_path().parent_path().parent_path());
+            else
+                append_if_has_cl_vs140(common7_tools.parent_path().parent_path());
         }
 
         // VS2015 instance from Program Files
-        append_if_has_cl(program_files_32_bit / "Microsoft Visual Studio 14.0");
+        append_if_has_cl_vs140(program_files_32_bit / "Microsoft Visual Studio 14.0");
 
         return instances;
     }