Fix: single-expression init functions in %py_class%

Author: t-kalinowski

NEWS.md

@@ -35,6 +35,9 @@
 
 - Fixed issue where `create_layer_wrapper()` would not include arguments
   with a `NULL` default value in the returned wrapper.
+  
+- Fixed issue in `r_to_py.R6ClassGenerator` (and `%py_class%`) where
+  single-expression `initialize` functions defined without `{` would error. 
 
 - Deprecated functions are no longer included in the package documentation index.
 

R/py-classes.R

@@ -170,8 +170,12 @@ as_py_method <- function(fn, name, env, convert) {
     }
 
     # __init__ must return NULL
-    if (name == "__init__")
-      body(fn)[[length(body(fn)) + 1L]] <- quote(invisible(NULL))
+    if (name == "__init__") {
+      body(fn) <- substitute({
+        body
+        invisible(NULL)
+      }, list(body = body(fn)))
+    }
 
     # python tensorflow does quite a bit of introspection on user-supplied
     # functions e.g., as part of determining which of the optional arguments

tests/testthat/test-py-class.R

@@ -84,3 +84,17 @@ test_that("%py_class% can be lazy about initing python", {
 
   expect_equal(res, 42)
 })
+
+
+test_that("%py_class% initialize", {
+  # check that single expression init functions defined with `{` work
+
+  NaiveSequential %py_class% {
+    initialize <- function(layers)
+      self$layers <- layers
+  }
+
+  x <- NaiveSequential(list(1, "2", 3))
+  expect_identical(x$layers, list(1, "2", 3))
+
+})