Use system CMake to unpack if available during 7z bootstrap (#793)

* Use installed CMake to unpack if available during 7z bootstrap

* Document fallbacks

include/vcpkg/tools.h

@@ -31,6 +31,8 @@ namespace vcpkg
         static constexpr StringLiteral ARIA2 = "aria2";
         static constexpr StringLiteral NODE = "node";
         static constexpr StringLiteral IFW_INSTALLER_BASE = "ifw_installerbase";
+        // This duplicate of CMake should only be used as a fallback to unpack
+        static constexpr StringLiteral CMAKE_SYSTEM = "cmake_system";
         // This duplicate of 7zip uses msiexec to unpack, which is a fallback for Windows 7.
         static constexpr StringLiteral SEVEN_ZIP_MSI = "7zip_msi";
         static constexpr StringLiteral PYTHON3 = "python3";
@@ -51,6 +53,7 @@ namespace vcpkg
                                                           const Path& exe_path);
 
     ExpectedL<Path> find_system_tar(const Filesystem& fs);
+    ExpectedL<Path> find_system_cmake(const Filesystem& fs);
 
     std::unique_ptr<ToolCache> get_tool_cache(Filesystem& fs,
                                               std::shared_ptr<const DownloadManager> downloader,

src/vcpkg/archives.cpp

@@ -217,6 +217,17 @@ namespace vcpkg
         fs.write_contents(to_path, contents, VCPKG_LINE_INFO);
     }
 
+    // We are trying to bootstrap vcpkg's copy of CMake which comes in a zipped file.
+    // If this is successful, we'll use the downloaded CMake for most extractions.
+    // We will also extract a portable 7z (using the bootstrapped CMake) to use when performance is required.
+    //
+    // We use the following methods to attempt this bootstrap, in order:
+    // 1) Search for a System32/tar.exe (available on Windows 10+)
+    //     tar.exe unpacks cmake.zip -> cmake.exe unpacks 7z.7z
+    // 2) Search for a user installed CMake on PATH and Program Files [(x86)]
+    //     (user) cmake.exe unpacks cmake.zip -> (vcpkg) cmake.exe unpacks 7z.7z
+    // 3) As a last resource, install 7zip using a MSI installer
+    //     msiexec installs 7zip.msi -> 7zip unpacks cmake.zip -> cmake.exe unpacks 7z.7z
     void win32_extract_bootstrap_zip(
         Filesystem& fs, const ToolCache& tools, MessageSink& status_sink, const Path& archive, const Path& to_path)
     {
@@ -229,19 +240,22 @@ namespace vcpkg
         if (fs.exists(tar_path, IgnoreErrors{}))
         {
             // On Windows 10, tar.exe is in the box.
-
-            // Example:
-            // tar unpacks cmake unpacks 7zip unpacks git
             extract_tar(tar_path, archive, to_path_partial);
         }
         else
         {
-            // On Windows <10, we attempt to use msiexec to unpack 7zip.
-
-            // Example:
-            // msiexec unpacks 7zip_msi unpacks cmake unpacks 7zip unpacks git
-            win32_extract_with_seven_zip(
-                tools.get_tool_path(Tools::SEVEN_ZIP_MSI, status_sink), archive, to_path_partial);
+            auto maybe_cmake_tool = find_system_cmake(fs);
+            if (maybe_cmake_tool)
+            {
+                // If the user has a CMake version installed we can use that to unpack.
+                extract_tar_cmake(maybe_cmake_tool.value_or_exit(VCPKG_LINE_INFO), archive, to_path_partial);
+            }
+            else
+            {
+                // On Windows <10, we attempt to use msiexec to unpack 7zip.
+                win32_extract_with_seven_zip(
+                    tools.get_tool_path(Tools::SEVEN_ZIP_MSI, status_sink), archive, to_path_partial);
+            }
         }
         fs.rename_with_retry(to_path_partial, to_path, VCPKG_LINE_INFO);
     }

src/vcpkg/tools.cpp

@@ -868,6 +868,10 @@ namespace vcpkg
                 {
                     return {find_system_tar(fs).value_or_exit(VCPKG_LINE_INFO), {}};
                 }
+                if (tool == Tools::CMAKE_SYSTEM)
+                {
+                    return {find_system_cmake(fs).value_or_exit(VCPKG_LINE_INFO), {}};
+                }
                 GenericToolProvider provider{tool};
                 return get_path(provider, status_sink);
             });
@@ -899,6 +903,39 @@ namespace vcpkg
         }
     }
 
+    ExpectedL<Path> find_system_cmake(const Filesystem& fs)
+    {
+        auto tools = fs.find_from_PATH(Tools::CMAKE);
+        if (!tools.empty())
+        {
+            return std::move(tools[0]);
+        }
+
+#if defined(_WIN32)
+        std::vector<Path> candidate_paths;
+        const auto& program_files = get_program_files_platform_bitness();
+        if (const auto pf = program_files.get())
+        {
+            auto path = *pf / "CMake" / "bin" / "cmake.exe";
+            if (fs.exists(path, IgnoreErrors{})) return path;
+        }
+
+        const auto& program_files_32_bit = get_program_files_32_bit();
+        if (const auto pf = program_files_32_bit.get())
+        {
+            auto path = *pf / "CMake" / "bin" / "cmake.exe";
+            if (fs.exists(path, IgnoreErrors{})) return path;
+        }
+#endif
+
+        return msg::format(msg::msgErrorMessage)
+            .append(msgToolFetchFailed, msg::tool_name = Tools::CMAKE)
+#if !defined(_WIN32)
+            .append(msgInstallWithSystemManager)
+#endif
+            ;
+    }
+
     std::unique_ptr<ToolCache> get_tool_cache(Filesystem& fs,
                                               std::shared_ptr<const DownloadManager> downloader,
                                               Path downloads,