From b59c996c9a7d3742132b195b8ac6740778ee880b Mon Sep 17 00:00:00 2001
From: Robrecht Cannoodt <rcannood@gmail.com>
Date: Fri, 11 Oct 2024 11:14:03 +0200
Subject: [PATCH] Return `NULL` when a record's related field is empty (#28)

* Add a simple unit test which queries laminlabs/lamindata

* update changelog

* Return `NULL` when a record's related field is empty

* update changelog

* add checks to test
---
 CHANGELOG.md                            | 2 ++
 R/Record.R                              | 9 ++++++++-
 tests/testthat/test-connect_lamindata.R | 8 +++++++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8689639..bd67e92 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -43,6 +43,8 @@
 
 * Fixed the parsing of the env files in `~/.lamin` due to changes in the lamindb-setup Python package (PR #12).
 
+* Return `NULL` when a record's related field is empty (PR #28).
+
 # laminr v0.0.1
 
 Initial POC implementation of the LaminDB API client for R.
diff --git a/R/Record.R b/R/Record.R
index cfc9b1d..415c578 100644
--- a/R/Record.R
+++ b/R/Record.R
@@ -163,7 +163,7 @@ Record <- R6::R6Class( # nolint object_name_linter
       } else if (key %in% private$.registry$get_field_names()) {
         field <- private$.registry$get_field(key)
 
-        ## TODO: use related_registry_class$get_records instead
+        # refetch the record to get the related data
         related_data <- private$.api$get_record(
           module_name = field$module_name,
           registry_name = field$registry_name,
@@ -171,10 +171,17 @@ Record <- R6::R6Class( # nolint object_name_linter
           select = key
         )[[key]]
 
+        # return NULL if the related data is NULL
+        if (is.null(related_data)) {
+          return(NULL)
+        }
+
+        # if the related data is not NULL, create a record class for it
         related_module <- private$.instance$get_module(field$related_module_name)
         related_registry <- related_module$get_registry(field$related_registry_name)
         related_registry_class <- related_registry$get_record_class()
 
+        # if the relation type is one-to-many or many-to-many, iterate over the list
         if (field$relation_type %in% c("one-to-one", "many-to-one")) {
           related_registry_class$new(related_data)
         } else {
diff --git a/tests/testthat/test-connect_lamindata.R b/tests/testthat/test-connect_lamindata.R
index e27bc47..126ac79 100644
--- a/tests/testthat/test-connect_lamindata.R
+++ b/tests/testthat/test-connect_lamindata.R
@@ -15,7 +15,13 @@ test_that("Connecting to lamindata works", {
   expect_equal(artifact$uid, "mePviem4DGM4SFzvLXf3")
   expect_equal(artifact$suffix, ".csv")
 
-  # try to fetch linked records
+  # try to fetch related field
   created_by <- artifact$created_by
   expect_equal(created_by$handle, "sunnyosun")
+
+  # access a related field which is empty for this record
+  expect_null(artifact$type) # one to one
+
+  expect_type(artifact$wells, "list") # one-to-many
+  expect_length(artifact$wells, 0)
 })