[vcpkg] Improve diagnostics around compiler tracking and toolset errors. 'Fixes' #15823. (#15825)

5 files changed, 67 insertions, 22 deletions

diff --git a/toolsrc/include/vcpkg/build.h b/toolsrc/include/vcpkg/build.h
index e873f0ea2..ed2724435 100644
--- a/toolsrc/include/vcpkg/build.h
+++ b/toolsrc/include/vcpkg/build.h
@@ -232,7 +232,9 @@ namespace vcpkg::Build
         const VcpkgPaths& m_paths;
     };
 
-    System::Command make_build_env_cmd(const PreBuildInfo& pre_build_info, const Toolset& toolset);
+    System::Command make_build_env_cmd(const PreBuildInfo& pre_build_info,
+                                       const Toolset& toolset,
+                                       View<Toolset> all_toolsets);
 
     struct ExtendedBuildResult
     {
diff --git a/toolsrc/include/vcpkg/vcpkgpaths.h b/toolsrc/include/vcpkg/vcpkgpaths.h
index 8a97b258e..643baf57e 100644
--- a/toolsrc/include/vcpkg/vcpkgpaths.h
+++ b/toolsrc/include/vcpkg/vcpkgpaths.h
@@ -148,6 +148,8 @@ namespace vcpkg
         /// </remarks>
         const Toolset& get_toolset(const Build::PreBuildInfo& prebuildinfo) const;
 
+        View<Toolset> get_all_toolsets() const;
+
         Files::Filesystem& get_filesystem() const;
 
         const System::Environment& get_action_env(const Build::AbiInfo& abi_info) const;
diff --git a/toolsrc/src/vcpkg/build.cpp b/toolsrc/src/vcpkg/build.cpp
index 8bbb5f2de..c22c20fea 100644
--- a/toolsrc/src/vcpkg/build.cpp
+++ b/toolsrc/src/vcpkg/build.cpp
@@ -299,11 +299,17 @@ namespace vcpkg::Build
         if (cmake_system_name == "Windows") return "";
         if (cmake_system_name == "WindowsStore") return "store";
 
-        Checks::exit_maybe_upgrade(VCPKG_LINE_INFO, "Unsupported vcvarsall target %s", cmake_system_name);
+        Checks::exit_maybe_upgrade(VCPKG_LINE_INFO,
+                                   "Error: Could not map VCPKG_CMAKE_SYSTEM_NAME '%s' to a vcvarsall platform. "
+                                   "Supported systems are '', 'Windows' and 'WindowsStore'.",
+                                   cmake_system_name);
     }
 
-    static CStringView to_vcvarsall_toolchain(const std::string& target_architecture, const Toolset& toolset)
+    static CStringView to_vcvarsall_toolchain(const std::string& target_architecture,
+                                              const Toolset& toolset,
+                                              View<Toolset> all_toolsets)
     {
+#if defined(_WIN32)
         auto maybe_target_arch = System::to_cpu_architecture(target_architecture);
         Checks::check_maybe_upgrade(
             VCPKG_LINE_INFO, maybe_target_arch.has_value(), "Invalid architecture string: %s", target_architecture);
@@ -318,19 +324,36 @@ namespace vcpkg::Build
             if (it != toolset.supported_architectures.end()) return it->name;
         }
 
-        Checks::exit_maybe_upgrade(VCPKG_LINE_INFO,
-                                   "Unsupported toolchain combination. Target was: %s but supported ones were:\n%s",
-                                   target_architecture,
-                                   Strings::join(",", toolset.supported_architectures, [](const ToolsetArchOption& t) {
-                                       return t.name.c_str();
-                                   }));
+        System::print2("Error: Unsupported toolchain combination.\n");
+        System::print2("Target was ",
+                       target_architecture,
+                       " but the chosen Visual Studio instance supports:\n    ",
+                       Strings::join(", ",
+                                     toolset.supported_architectures,
+                                     [](const ToolsetArchOption& t) { return t.name.c_str(); }),
+                       "\nVcpkg selected ",
+                       fs::u8string(toolset.visual_studio_root_path),
+                       " as the Visual Studio instance.\nDetected instances:\n",
+                       Strings::join("",
+                                     all_toolsets,
+                                     [](const Toolset& t) {
+                                         return Strings::concat("    ", fs::u8string(t.visual_studio_root_path), '\n');
+                                     }),
+                       "\nSee "
+                       "https://github.com/microsoft/vcpkg/blob/master/docs/users/triplets.md#VCPKG_VISUAL_STUDIO_PATH "
+                       "for more information.\n");
+        Checks::exit_maybe_upgrade(VCPKG_LINE_INFO);
+#else
+        Checks::exit_with_message(VCPKG_LINE_INFO,
+                                  "Error: vcvars-based toolchains are only usable on Windows platforms.");
+#endif
     }
 
 #if defined(_WIN32)
     const System::Environment& EnvCache::get_action_env(const VcpkgPaths& paths, const AbiInfo& abi_info)
     {
-        auto build_env_cmd =
-            make_build_env_cmd(*abi_info.pre_build_info, abi_info.toolset.value_or_exit(VCPKG_LINE_INFO));
+        auto build_env_cmd = make_build_env_cmd(
+            *abi_info.pre_build_info, abi_info.toolset.value_or_exit(VCPKG_LINE_INFO), paths.get_all_toolsets());
 
         const auto& base_env = envs.get_lazy(abi_info.pre_build_info->passthrough_env_vars, [&]() -> EnvMapEntry {
             std::unordered_map<std::string, std::string> env;
@@ -440,7 +463,9 @@ namespace vcpkg::Build
         });
     }
 
-    System::Command make_build_env_cmd(const PreBuildInfo& pre_build_info, const Toolset& toolset)
+    System::Command make_build_env_cmd(const PreBuildInfo& pre_build_info,
+                                       const Toolset& toolset,
+                                       View<Toolset> all_toolsets)
     {
         if (!pre_build_info.using_vcvars()) return {};
 
@@ -450,7 +475,7 @@ namespace vcpkg::Build
             tonull = "";
         }
 
-        const auto arch = to_vcvarsall_toolchain(pre_build_info.target_architecture, toolset);
+        const auto arch = to_vcvarsall_toolchain(pre_build_info.target_architecture, toolset, all_toolsets);
         const auto target = to_vcvarsall_target(pre_build_info.cmake_system_name);
 
         return System::Command{"cmd"}.string_arg("/c").raw_arg(
@@ -566,7 +591,8 @@ namespace vcpkg::Build
         std::ofstream out_file(stdoutlog.native().c_str(), std::ios::out | std::ios::binary | std::ios::trunc);
         Checks::check_exit(VCPKG_LINE_INFO, out_file, "Failed to open '%s' for writing", fs::u8string(stdoutlog));
         CompilerInfo compiler_info;
-        System::cmd_execute_and_stream_lines(
+        std::string buf;
+        int rc = System::cmd_execute_and_stream_lines(
             command,
             [&](StringView s) {
                 static const StringLiteral s_hash_marker = "#COMPILER_HASH#";
@@ -585,6 +611,7 @@ namespace vcpkg::Build
                     compiler_info.id = s.data() + s_id_marker.size();
                 }
                 Debug::print(s, '\n');
+                Strings::append(buf, s, '\n');
                 out_file.write(s.data(), s.size()).put('\n');
                 Checks::check_exit(
                     VCPKG_LINE_INFO, out_file, "Error occurred while writing '%s'", fs::u8string(stdoutlog));
@@ -592,19 +619,24 @@ namespace vcpkg::Build
             env);
         out_file.close();
 
-        if (compiler_info.hash.empty())
+        if (compiler_info.hash.empty() || rc != 0)
         {
             Debug::print("Compiler information tracking can be disabled by passing --",
                          VcpkgCmdArguments::FEATURE_FLAGS_ARG,
                          "=-",
                          VcpkgCmdArguments::COMPILER_TRACKING_FEATURE,
                          "\n");
+
+            System::print2("Error: while detecting compiler information:\nThe log content at ",
+                           fs::u8string(stdoutlog),
+                           " is:\n",
+                           buf);
+            Checks::exit_with_message(VCPKG_LINE_INFO,
+                                      "Error: vcpkg was unable to detect the active compiler's information. See above "
+                                      "for the CMake failure output.");
         }
-        Checks::check_exit(VCPKG_LINE_INFO,
-                           !compiler_info.hash.empty(),
-                           "Error occurred while detecting compiler information. Pass `--debug` for more information.");
 
-        Debug::print("Detecting compiler hash for triplet ", triplet, ": ", compiler_info.hash, "\n");
+        Debug::print("Detected compiler hash for triplet ", triplet, ": ", compiler_info.hash, "\n");
         return compiler_info;
     }
 
diff --git a/toolsrc/src/vcpkg/commands.env.cpp b/toolsrc/src/vcpkg/commands.env.cpp
index c0bec17dc..f129f0262 100644
--- a/toolsrc/src/vcpkg/commands.env.cpp
+++ b/toolsrc/src/vcpkg/commands.env.cpp
@@ -48,7 +48,7 @@ namespace vcpkg::Commands::Env
         const Build::PreBuildInfo pre_build_info(
             paths, triplet, var_provider.get_generic_triplet_vars(triplet).value_or_exit(VCPKG_LINE_INFO));
         const Toolset& toolset = paths.get_toolset(pre_build_info);
-        auto build_env_cmd = Build::make_build_env_cmd(pre_build_info, toolset);
+        auto build_env_cmd = Build::make_build_env_cmd(pre_build_info, toolset, paths.get_all_toolsets());
 
         std::unordered_map<std::string, std::string> extra_env = {};
         const bool add_bin = Util::Sets::contains(options.switches, OPTION_BIN);
diff --git a/toolsrc/src/vcpkg/vcpkgpaths.cpp b/toolsrc/src/vcpkg/vcpkgpaths.cpp
index e6fa3a0a5..b9f1f3f9c 100644
--- a/toolsrc/src/vcpkg/vcpkgpaths.cpp
+++ b/toolsrc/src/vcpkg/vcpkgpaths.cpp
@@ -980,8 +980,7 @@ If you wish to silence this error and use classic mode, you can:
 #if !defined(_WIN32)
         Checks::exit_maybe_upgrade(VCPKG_LINE_INFO, "Cannot build windows triplets from non-windows.");
 #else
-        const std::vector<Toolset>& vs_toolsets = m_pimpl->toolsets.get_lazy(
-            [this]() { return VisualStudio::find_toolset_instances_preferred_first(*this); });
+        View<Toolset> vs_toolsets = get_all_toolsets();
 
         std::vector<const Toolset*> candidates = Util::fmap(vs_toolsets, [](auto&& x) { return &x; });
         const auto tsv = prebuildinfo.platform_toolset.get();
@@ -1029,6 +1028,16 @@ If you wish to silence this error and use classic mode, you can:
 #endif
     }
 
+    View<Toolset> VcpkgPaths::get_all_toolsets() const
+    {
+#if defined(_WIN32)
+        return m_pimpl->toolsets.get_lazy(
+            [this]() { return VisualStudio::find_toolset_instances_preferred_first(*this); });
+#else
+        return {};
+#endif
+    }
+
     const System::Environment& VcpkgPaths::get_action_env(const Build::AbiInfo& abi_info) const
     {
         return m_pimpl->m_env_cache.get_action_env(*this, abi_info);