Add switch to force classic mode. (#1535)

A customer wanted to run vcpkg in a place where they could not control that a `vcpkg.json` was in a directory above, and requested a way to force classic mode. One used to be able to do this with the `--no-manifest` feature flag, but that was removed some years ago.

This adds a new switch, `--classic`, which effectively skips looking for a manifest.

azure-pipelines/end-to-end-tests-dir/manifests.ps1

@@ -185,3 +185,17 @@ Throw-IfFailed
 Write-Trace "test manifest features: self-reference, features = [a], with overlay"
 Run-Vcpkg install @manifestDirArgs --x-feature=a "--overlay-ports=$manifestDir/manifest-test"
 Throw-IfFailed
+
+Write-Trace "test manifest install with specific package names fails"
+$output = Run-VcpkgAndCaptureOutput install @manifestDirArgs vcpkg-empty-port
+Throw-IfNotFailed
+Throw-IfNonContains -Expected 'error: In manifest mode, `vcpkg install` does not support individual package arguments.' -Actual $output
+
+Write-Trace "test manifest install with specific package names forced to classic mode succeeds"
+$output = Run-VcpkgAndCaptureOutput install @manifestDirArgs --classic vcpkg-empty-port
+Throw-IfFailed
+$expected = @"
+The following packages will be built and installed:
+    vcpkg-empty-port:
+"@
+Throw-IfNonContains -Expected $expected -Actual $output

include/vcpkg/base/contractual-constants.h

@@ -187,6 +187,7 @@ namespace vcpkg
     inline constexpr StringLiteral SwitchBuiltinPortsRoot = "builtin-ports-root";
     inline constexpr StringLiteral SwitchBuiltinRegistryVersionsDir = "builtin-registry-versions-dir";
     inline constexpr StringLiteral SwitchCIBaseline = "ci-baseline";
+    inline constexpr StringLiteral SwitchClassic = "classic";
     inline constexpr StringLiteral SwitchCleanAfterBuild = "clean-after-build";
     inline constexpr StringLiteral SwitchCleanBuildtreesAfterBuild = "clean-buildtrees-after-build";
     inline constexpr StringLiteral SwitchCleanDownloadsAfterBuild = "clean-downloads-after-build";

include/vcpkg/base/message-data.inc.h

@@ -1358,6 +1358,7 @@ DECLARE_MESSAGE(
     (),
     "",
     "Environment variable VCPKG_FORCE_SYSTEM_BINARIES must be set on arm, s390x, ppc64le and riscv platforms.")
+DECLARE_MESSAGE(ForceClassicMode, (), "", "Force classic mode, even if a manifest could be found.")
 DECLARE_MESSAGE(FormattedParseMessageExpressionPrefix, (), "", "on expression:")
 DECLARE_MESSAGE(ForMoreHelp,
                 (),

include/vcpkg/vcpkgcmdarguments.h

@@ -212,6 +212,7 @@ namespace vcpkg
 
         Optional<std::string> vcpkg_root_dir_arg;
         Optional<std::string> vcpkg_root_dir_env;
+        Optional<bool> force_classic_mode;
         Optional<std::string> manifest_root_dir;
 
         Optional<std::string> buildtrees_root_dir;

locales/messages.json

@@ -807,6 +807,7 @@
   "FollowingPackagesUpgraded": "The following packages are up-to-date:",
   "ForMoreHelp": "For More Help",
   "_ForMoreHelp.comment": "Printed before a suggestion for the user to run `vcpkg help <topic>`",
+  "ForceClassicMode": "Force classic mode, even if a manifest could be found.",
   "ForceSystemBinariesOnWeirdPlatforms": "Environment variable VCPKG_FORCE_SYSTEM_BINARIES must be set on arm, s390x, ppc64le and riscv platforms.",
   "FormattedParseMessageExpressionPrefix": "on expression:",
   "GHAParametersMissing": "The GHA binary source requires the ACTIONS_RUNTIME_TOKEN and ACTIONS_CACHE_URL environment variables to be set. See {url} for details.",

src/vcpkg/vcpkgcmdarguments.cpp

@@ -336,6 +336,8 @@ namespace vcpkg
             args.host_triplet,
             msg::format(msgSpecifyHostArch,
                         msg::env_var = format_environment_variable(EnvironmentVariableVcpkgDefaultHostTriplet)));
+        args.parser.parse_switch(
+            SwitchClassic, StabilityTag::Standard, args.force_classic_mode, msg::format(msgForceClassicMode));
         args.parser.parse_option(SwitchManifestRoot, StabilityTag::Experimental, args.manifest_root_dir);
         args.parser.parse_option(SwitchBuildtreesRoot,
                                  StabilityTag::Experimental,

src/vcpkg/vcpkgpaths.cpp

@@ -259,14 +259,17 @@ namespace
 
     Path compute_manifest_dir(const ReadOnlyFilesystem& fs, const VcpkgCmdArguments& args, const Path& original_cwd)
     {
+        if (args.force_classic_mode.value_or(false))
+        {
+            return Path{};
+        }
+
         if (auto manifest_root_dir = args.manifest_root_dir.get())
         {
             return fs.almost_canonical(*manifest_root_dir, VCPKG_LINE_INFO);
         }
-        else
-        {
-            return fs.find_file_recursively_up(original_cwd, "vcpkg.json", VCPKG_LINE_INFO);
-        }
+
+        return fs.find_file_recursively_up(original_cwd, FileVcpkgDotJson, VCPKG_LINE_INFO);
     }
 
     // This structure holds members for VcpkgPathsImpl that don't require explicit initialization/destruction