validations: Limit ref. validation to only LocalOrigin(s) (#1379)

* validations: Limit ref. validation to only LocalOrigin(s)

* validations: add test for disabled origins

internal/decoder/validations/unreferenced_origin.go

@@ -27,6 +27,13 @@ func UnreferencedOrigins(ctx context.Context, pathCtx *decoder.PathContext) lang
 			continue
 		}
 
+		_, ok = origin.(reference.LocalOrigin)
+		if !ok {
+			// we avoid reporting on origins outside of the current module
+			// for now, to reduce complexity and reduce performance impact
+			continue
+		}
+
 		// we only initially validate variables
 		// resources and data sources can have unknown schema
 		// and will be researched at a later point

internal/decoder/validations/unreferenced_origin_test.go

@@ -50,6 +50,28 @@ func TestUnreferencedOrigins(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "unsupported path origins (module input)",
+			origins: reference.Origins{
+				reference.PathOrigin{
+					Range: hcl.Range{
+						Filename: "test.tf",
+						Start:    hcl.Pos{},
+						End:      hcl.Pos{},
+					},
+					TargetAddr: lang.Address{
+						lang.RootStep{Name: "var"},
+						lang.AttrStep{Name: "foo"},
+					},
+					TargetPath: lang.Path{
+						Path:       "./submodule",
+						LanguageID: "terraform",
+					},
+					Constraints: reference.OriginConstraints{},
+				},
+			},
+			want: lang.DiagnosticsMap{},
+		},
 		{
 			name: "many undeclared variables",
 			origins: reference.Origins{