add a csharp_library_set rule

csharp/defs.bzl

@@ -11,6 +11,10 @@ load(
     "//csharp/private:rules/library.bzl",
     _csharp_library = "csharp_library",
 )
+load(
+    "//csharp/private:rules/library_set.bzl",
+    _csharp_library_set = "csharp_library_set",
+)
 load(
     "//csharp/private:rules/nunit_test.bzl",
     _csharp_nunit_test = "csharp_nunit_test",
@@ -32,6 +36,7 @@ load(
 
 csharp_binary = _csharp_binary
 csharp_library = _csharp_library
+csharp_library_set = _csharp_library_set
 csharp_nunit_test = _csharp_nunit_test
 csharp_register_toolchains = _csharp_register_toolchains
 csharp_repositories = _csharp_repositories

csharp/private/rules/library_set.bzl

@@ -0,0 +1,45 @@
+load(
+    "@d2l_rules_csharp//csharp/private:common.bzl",
+    "collect_transitive_info",
+    "fill_in_missing_frameworks",
+)
+load("@d2l_rules_csharp//csharp/private:providers.bzl", "AnyTargetFramework", "CSharpAssembly")
+
+def _library_set(ctx):
+    files = []
+
+    tfm = ctx.attr.target_framework
+
+    (refs, runfiles) = collect_transitive_info(ctx.attr.deps, tfm)
+
+    providers = {
+        tfm: CSharpAssembly[tfm](
+            out = None,
+            refout = None,
+            pdb = None,
+            deps = ctx.attr.deps,
+            transitive_refs = refs,
+            transitive_runfiles = runfiles,
+            actual_tfm = tfm
+        ),
+    }
+
+    fill_in_missing_frameworks(providers)
+
+    return providers.values()
+
+csharp_library_set = rule(
+    _library_set,
+    doc = "Defines a set of C# libraries to be depended on together",
+    attrs = {
+        "target_framework": attr.string(
+            doc = "The target framework for this set of libraries",
+            mandatory = True,
+        ),
+        "deps": attr.label_list(
+            doc = "The set of libraries",
+            providers = AnyTargetFramework,
+        ),
+    },
+    executable = False,
+)