fix: order union properties to avoid type collision

changelog/@unreleased/pr-749.v2.yml

@@ -0,0 +1,5 @@
+type: fix
+fix:
+  description: order union properties to avoid type collision
+  links:
+  - https://github.com/palantir/conjure-python/pull/749

conjure-python-core/src/main/java/com/palantir/conjure/python/poet/UnionSnippet.java

@@ -178,22 +178,16 @@ default void emit(PythonPoetWriter poetWriter) {
             poetWriter.decreaseIndent();
 
             // python @builtins.property for each member of the union
-            options().forEach(option -> {
-                poetWriter.writeLine();
-
-                poetWriter.writeIndentedLine("@builtins.property");
-                poetWriter.writeIndentedLine(
-                        String.format("def %s(self) -> Optional[%s]:", propertyName(option), option.myPyType()));
+            options().stream()
+                    .filter(option -> !propertyName(option).equals("float"))
+                    .forEach(option -> emitProperty(poetWriter, option));
 
-                poetWriter.increaseIndent();
-                option.docs().ifPresent(docs -> {
-                    poetWriter.writeIndentedLine("\"\"\"");
-                    poetWriter.writeIndentedLine(docs.get().trim());
-                    poetWriter.writeIndentedLine("\"\"\"");
-                });
-                poetWriter.writeIndentedLine(String.format("return self.%s", fieldName(option)));
-                poetWriter.decreaseIndent();
-            });
+            // properties with builtin names must come after other properties
+            // can be removed once these names are properly sanitized but
+            // that will require a breaking change and major version bump
+            options().stream()
+                    .filter(option -> propertyName(option).equals("float"))
+                    .forEach(option -> emitProperty(poetWriter, option));
 
             String visitorName = String.format("%sVisitor", className());
             String definitionVisitorName = String.format("%sVisitor", definitionName());
@@ -246,6 +240,23 @@ default void emit(PythonPoetWriter poetWriter) {
         });
     }
 
+    private static void emitProperty(PythonPoetWriter poetWriter, PythonField option) {
+        poetWriter.writeLine();
+
+        poetWriter.writeIndentedLine("@builtins.property");
+        poetWriter.writeIndentedLine(
+                String.format("def %s(self) -> Optional[%s]:", propertyName(option), option.myPyType()));
+
+        poetWriter.increaseIndent();
+        option.docs().ifPresent(docs -> {
+            poetWriter.writeIndentedLine("\"\"\"");
+            poetWriter.writeIndentedLine(docs.get().trim());
+            poetWriter.writeIndentedLine("\"\"\"");
+        });
+        poetWriter.writeIndentedLine(String.format("return self.%s", fieldName(option)));
+        poetWriter.decreaseIndent();
+    }
+
     class Builder extends ImmutableUnionSnippet.Builder {}
 
     static Builder builder() {

conjure-python-core/src/test/resources/types/example-types.yml

@@ -172,3 +172,9 @@ types:
         alias: RecursiveObjectAlias
       CollectionAliasExample:
         alias: map<StringAliasExample, RecursiveObjectAlias>
+      UnionWithBuiltinVariantName:
+        union:
+          # the name of this variant is 'float' which conflicts with the python type 'float'
+          float: double
+          # the python type for this field is 'float' which conflicts with the variant name above
+          double: double