From d956e69e8b55dc2248b902490a138a46f02f9e55 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 1 Feb 2023 14:32:04 +0200
Subject: Add --sys-no-stub bpkg-pkg-build option to allow sys: packages
 without stubs

---
 bpkg/pkg-build.cli                     | 10 +++++++++-
 bpkg/pkg-build.cxx                     | 16 +++++++++++++---
 bpkg/system-package-manager-debian.cxx | 23 +++++++++++++----------
 bpkg/system-package-manager.cxx        |  2 ++
 4 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/bpkg/pkg-build.cli b/bpkg/pkg-build.cli
index 740764b..41a8432 100644
--- a/bpkg/pkg-build.cli
+++ b/bpkg/pkg-build.cli
@@ -107,7 +107,8 @@ namespace bpkg
      manager is supported, then the automatic installation of an available
      package can be requested with the \cb{--sys-install} option. Note that if
      the version is not explicitly specified, then at least a stub package
-     must be available from one of the repositories.
+     must be available from one of the repositories unless the
+     \cb{--sys-no-stub} option is specified.
 
      Finally, a package can be specified as either the path to the package
      archive (<file>) or to the package directory (<dir>\cb{/}; note that it
@@ -437,6 +438,13 @@ namespace bpkg
        This option only makes sense together with \cb{--sys-install}."
     }
 
+    bool --sys-no-stub
+    {
+      "Do no require a stub for packages specified with the \cb{sys} scheme.
+       Note that this option has effect only if the system package manager
+       interactions are supported and not disabled."
+    }
+
     bool --sys-yes
     {
       "Assume the answer to the system package manager prompts is \cb{yes}.
diff --git a/bpkg/pkg-build.cxx b/bpkg/pkg-build.cxx
index 4d90df2..9e5e1bb 100644
--- a/bpkg/pkg-build.cxx
+++ b/bpkg/pkg-build.cxx
@@ -1714,11 +1714,21 @@ namespace bpkg
             aps = find_available_all (current_configs, nm);
 
             // If no source/stub for the package (and thus no mapping), issue
-            // diagnostics consistent with other such places.
+            // diagnostics consistent with other such places unless explicitly
+            // allowed by the user.
             //
             if (aps.empty ())
-              fail << "unknown package " << nm <<
-                info << "consider specifying " << nm << "/*";
+            {
+              if (!o.sys_no_stub ())
+                fail << "unknown package " << nm <<
+                  info << "consider specifying --sys-no-stub or " << nm << "/*";
+
+              // Add the stub package to the imaginary system repository (like
+              // the user-specified case below).
+              //
+              if (stubs != nullptr)
+                stubs->push_back (make_shared<available_package> (nm));
+            }
           }
 
           // This covers both our diagnostics below as well as anything that
diff --git a/bpkg/system-package-manager-debian.cxx b/bpkg/system-package-manager-debian.cxx
index 06b5060..998c4f4 100644
--- a/bpkg/system-package-manager-debian.cxx
+++ b/bpkg/system-package-manager-debian.cxx
@@ -891,10 +891,12 @@ namespace bpkg
              << os_release_.name_id << " package name";
         });
 
-      strings ns (system_package_names (*aps,
-                                        os_release_.name_id,
-                                        os_release_.version_id,
-                                        os_release_.like_ids));
+      strings ns;
+      if (!aps->empty ())
+        ns = system_package_names (*aps,
+                                   os_release_.name_id,
+                                   os_release_.version_id,
+                                   os_release_.like_ids);
       if (ns.empty ())
       {
         // Attempt to automatically translate our package name (see above for
@@ -1231,12 +1233,13 @@ namespace bpkg
       //
       string sv (r->system_version, 0, r->system_version.rfind ('-'));
 
-      optional<version> v (
-        downstream_package_version (sv,
-                                    *aps,
-                                    os_release_.name_id,
-                                    os_release_.version_id,
-                                    os_release_.like_ids));
+      optional<version> v;
+      if (!aps->empty ())
+        v = downstream_package_version (sv,
+                                        *aps,
+                                        os_release_.name_id,
+                                        os_release_.version_id,
+                                        os_release_.like_ids);
 
       if (!v)
       {
diff --git a/bpkg/system-package-manager.cxx b/bpkg/system-package-manager.cxx
index 9f5dad0..5089db1 100644
--- a/bpkg/system-package-manager.cxx
+++ b/bpkg/system-package-manager.cxx
@@ -280,6 +280,8 @@ namespace bpkg
                               const string& version_id,
                               const vector<string>& like_ids)
   {
+    assert (!aps.empty ());
+
     semantic_version vid (parse_version_id (version_id, name_id));
 
     // Iterate over the passed available packages (in version descending
-- 
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