Allow absent inputs to use import contexts

internal/engine/source_version_test.go

@@ -539,6 +539,41 @@ func TestSourceVersionNoSourceMainRetainsAbsentCallback(t *testing.T) {
 			if !called || len(result.diagnostics) != 0 || result.evidence != nil || result.payload != nil {
 				t.Fatalf("NoSource result = %#v, callback called = %v", result, called)
 			}
+
+			type config struct{}
+			for _, reject := range []bool{false, true} {
+				called = false
+				definition := Definition[config]{Version: &VersionRule{
+					Path: Keys("version"),
+					Check: func(version Version, _ *Validation) error {
+						called = true
+						if version != (Version{}) {
+							t.Errorf("NoSource load version = %#v", version)
+						}
+						if reject {
+							return errors.New("rejected absent main")
+						}
+						return nil
+					},
+				}}
+				loaded, loadErr := testLoad(NoSource(), Options[config]{
+					Definition: definition, Imports: true, SourceVersionMode: test.mode,
+				})
+				if !called {
+					t.Fatal("NoSource load did not call the source-version checker")
+				}
+				if reject {
+					var failure *LoadError
+					if !errors.As(loadErr, &failure) {
+						t.Fatalf("rejected NoSource load = %v, want *LoadError", loadErr)
+					}
+					requireSourceVersionDiagnostic(t, failure.Diagnostics(), CodeVersionHookFailed, "/version")
+					continue
+				}
+				if loadErr != nil || loaded == nil || len(loaded.Sources()) != 0 {
+					t.Fatalf("accepted NoSource load = %#v, %v", loaded, loadErr)
+				}
+			}
 		})
 	}
 }