Add restrictions against referencing Mapping/Listing/Dynamic.default, Module.output, and any property of an external class

HT154 · HT154 · commit aa424230de3e · 2026-05-21T11:40:22.000-07:00
diff --git a/pkl-core/src/main/java/org/pkl/core/runtime/VmReference.java b/pkl-core/src/main/java/org/pkl/core/runtime/VmReference.java
@@ -18,6 +18,7 @@
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.source.SourceSection;
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -183,21 +184,30 @@ private static void getCandidatePropertyType(PType type, String property, Set<PT
       result.add(type);
       return;
     }
-    if (!(type instanceof PType.Class clazz)) {
-      return;
-    }
+    // restriction: only class types can have their properties referenced
+    if (!(type instanceof PType.Class clazz)) return;
+    // restriction: cannot reference properties of external classes
+    if (clazz.getPClass().isExternal()) return;
     if (clazz.getPClass().getInfo() == PClassInfo.Dynamic) {
-      result.add(PType.UNKNOWN);
+      // restriction: cannot reference Dynamic.default
+      if (!property.equals("default")) result.add(PType.UNKNOWN);
       return;
     }
+    // restriction: cannot reference Listing/Mapping.default
     if (clazz.getPClass().getInfo() == PClassInfo.Listing
-        || clazz.getPClass().getInfo() == PClassInfo.List
-        || clazz.getPClass().getInfo() == PClassInfo.Mapping
-        || clazz.getPClass().getInfo() == PClassInfo.Map) {
+        || clazz.getPClass().getInfo() == PClassInfo.Mapping) {
       return;
     }
-    // Typed
+    // restriction: cannot reference Module.output.
+    //   generalized: properties originally defined in external classes; the only extant example.
+    // This is implemented specifically because this is the only case where an external class
+    //   containing a property can be subclassed.
+    // And this can't check prop.getOwner().isExternal() because fully overriding the property with
+    //   a new type annotation means the owner isn't Module.
+    if (clazz.getPClass().isModuleClass() && property.equals("output")) return;
+
     var prop = clazz.getPClass().getAllProperties().get(property);
+    // restriction: cannot reference external properties
     if (prop == null || prop.isExternal()) {
       return;
     }
@@ -376,9 +386,11 @@ public Reference export() {
   }
 
   public PType exportReferentType() {
-    return candidateTypes.size() == 1
-        ? candidateTypes.iterator().next()
-        : new PType.Union(List.copyOf(candidateTypes));
+    if (candidateTypes.size() == 1) return candidateTypes.iterator().next();
+    var types = new ArrayList<>(candidateTypes);
+    // sort multiple candidate types to ensure stable output
+    types.sort(Comparator.comparing(Object::toString));
+    return new PType.Union(types);
   }
 
   public PType exportType() {
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input-helper/errors/ReferencedModule.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input-helper/errors/ReferencedModule.pkl
@@ -0,0 +1 @@
+foo: String
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input-helper/errors/ReferencedModuleWithOutputOverride.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input-helper/errors/ReferencedModuleWithOutputOverride.pkl
@@ -0,0 +1,5 @@
+foo: String
+
+hidden output: ModuleOutput = new {
+  text = foo
+}
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/api/reference.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/api/reference.pkl
@@ -113,3 +113,4 @@ j: K = new {
 
 refInterpolation = "\(aRef.outputs.someListing[1])"
 kInterpolation = "\(k)"
+aValuesJoined = k.aValues.join("\n").replaceAll(Regex("@[a-z0-9]+"), "@<addr>")
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference13.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference13.pkl
@@ -0,0 +1,8 @@
+import "pkl:ref"
+
+class D extends ref.Domain {
+  function referenceToString(data: Any, path: List<ref.Access>): String = throw("not supported")
+}
+local d: D = new {}
+
+test = ref.Reference(d, Mapping, "").default
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference14.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference14.pkl
@@ -0,0 +1,8 @@
+import "pkl:ref"
+
+class D extends ref.Domain {
+  function referenceToString(data: Any, path: List<ref.Access>): String = throw("not supported")
+}
+local d: D = new {}
+
+test = ref.Reference(d, Listing, "").default
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference15.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference15.pkl
@@ -0,0 +1,8 @@
+import "pkl:ref"
+
+class D extends ref.Domain {
+  function referenceToString(data: Any, path: List<ref.Access>): String = throw("not supported")
+}
+local d: D = new {}
+
+test = ref.Reference(d, Dynamic, "").default
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference16.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference16.pkl
@@ -0,0 +1,10 @@
+import "pkl:ref"
+
+import ".../input-helper/errors/ReferencedModule.pkl"
+
+class D extends ref.Domain {
+  function referenceToString(data: Any, path: List<ref.Access>): String = throw("not supported")
+}
+local d: D = new {}
+
+test = ref.Reference(d, ReferencedModule.getClass(), "").output
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference17.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/errors/reference17.pkl
@@ -0,0 +1,10 @@
+import "pkl:ref"
+
+import ".../input-helper/errors/ReferencedModuleWithOutputOverride.pkl"
+
+class D extends ref.Domain {
+  function referenceToString(data: Any, path: List<ref.Access>): String = throw("not supported")
+}
+local d: D = new {}
+
+test = ref.Reference(d, ReferencedModuleWithOutputOverride.getClass(), "").output
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/api/reference.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/api/reference.pcf
@@ -48,4 +48,12 @@ j {
   splitUnion = "${a.outputs.someListing}"
 }
 refInterpolation = "${a.outputs.someListing[1]}"
-kInterpolation = "new K { aId = Reference(new D {}, String, new A { name = \"a\"; id = \"some-a-value\" }).id; bId = Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).id; aProperties = Reference(new D {}, reference#AProperties, new A { name = \"a\"; id = \"some-a-value\" }).outputs; bProperties = Reference(new D {}, reference#BProperties, new B { name = \"b\"; id = \"some-b-value\" }).outputs; aValues { Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.foo; Reference(new D {}, Null | Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someMapping[\"key\"]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someMap[new MapKey { k = 123 }]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someListing[0]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someList[9223372036854775807]; Reference(new D {}, Int, new B { name = \"b\"; id = \"some-b-value\" }).outputs.nonString }; bValues { Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.foo; Reference(new D {}, Null | String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someMapping[\"key\"]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someMap[new MapKey { k = 123 }]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someListing[0]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someList[9223372036854775807]; Reference(new D {}, String, new A { name = \"a\"; id = \"some-a-value\" }).outputs.nonInt }; splitUnion = null }"
+kInterpolation = "new K { aId = Reference(new D {}, String, new A { name = \"a\"; id = \"some-a-value\" }).id; bId = Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).id; aProperties = Reference(new D {}, reference#AProperties, new A { name = \"a\"; id = \"some-a-value\" }).outputs; bProperties = Reference(new D {}, reference#BProperties, new B { name = \"b\"; id = \"some-b-value\" }).outputs; aValues { Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.foo; Reference(new D {}, Int | Null, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someMapping[\"key\"]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someMap[new MapKey { k = 123 }]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someListing[0]; Reference(new D {}, Int, new A { name = \"a\"; id = \"some-a-value\" }).outputs.someList[9223372036854775807]; Reference(new D {}, Int, new B { name = \"b\"; id = \"some-b-value\" }).outputs.nonString }; bValues { Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.foo; Reference(new D {}, Null | String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someMapping[\"key\"]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someMap[new MapKey { k = 123 }]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someListing[0]; Reference(new D {}, String, new B { name = \"b\"; id = \"some-b-value\" }).outputs.someList[9223372036854775807]; Reference(new D {}, String, new A { name = \"a\"; id = \"some-a-value\" }).outputs.nonInt }; splitUnion = null }"
+aValuesJoined = """
+  org.pkl.core.runtime.VmReference@<addr>
+  org.pkl.core.runtime.VmReference@<addr>
+  org.pkl.core.runtime.VmReference@<addr>
+  org.pkl.core.runtime.VmReference@<addr>
+  org.pkl.core.runtime.VmReference@<addr>
+  org.pkl.core.runtime.VmReference@<addr>
+  """
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference13.err b/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference13.err
@@ -0,0 +1,14 @@
+–– Pkl Error ––
+Cannot find property `default` in object of type `pkl.ref#Reference<reference13#D, Mapping>`.
+
+x | test = ref.Reference(d, Mapping, "").default
+           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at reference13#test (file:///$snippetsDir/input/errors/reference13.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference14.err b/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference14.err
@@ -0,0 +1,14 @@
+–– Pkl Error ––
+Cannot find property `default` in object of type `pkl.ref#Reference<reference14#D, Listing>`.
+
+x | test = ref.Reference(d, Listing, "").default
+           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at reference14#test (file:///$snippetsDir/input/errors/reference14.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference15.err b/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference15.err
@@ -0,0 +1,14 @@
+–– Pkl Error ––
+Cannot find property `default` in object of type `pkl.ref#Reference<reference15#D, Dynamic>`.
+
+x | test = ref.Reference(d, Dynamic, "").default
+           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at reference15#test (file:///$snippetsDir/input/errors/reference15.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference16.err b/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference16.err
@@ -0,0 +1,14 @@
+–– Pkl Error ––
+Cannot find property `output` in object of type `pkl.ref#Reference<reference16#D, ReferencedModule>`.
+
+xx | test = ref.Reference(d, ReferencedModule.getClass(), "").output
+            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at reference16#test (file:///$snippetsDir/input/errors/reference16.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference17.err b/pkl-core/src/test/files/LanguageSnippetTests/output/errors/reference17.err
@@ -0,0 +1,14 @@
+–– Pkl Error ––
+Cannot find property `output` in object of type `pkl.ref#Reference<reference17#D, ReferencedModuleWithOutputOverride>`.
+
+xx | test = ref.Reference(d, ReferencedModuleWithOutputOverride.getClass(), "").output
+            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at reference17#test (file:///$snippetsDir/input/errors/reference17.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)

Original file line number	Diff line number	Diff line change
`@@ -113,3 +113,4 @@ j: K = new {`
`113`	`113`
`114`	`114`	`refInterpolation = "\(aRef.outputs.someListing[1])"`
`115`	`115`	`kInterpolation = "\(k)"`
	`116`	`+aValuesJoined = k.aValues.join("\n").replaceAll(Regex("@[a-z0-9]+"), "@<addr>")`