From 170359d8409a0d07455715d369eb59535d58b8a4 Mon Sep 17 00:00:00 2001
From: Jonathan Bernard <jonathan@jdbernard.com>
Date: Wed, 2 Sep 2026 11:50:44 -0500
Subject: [PATCH] Fix distinct type row mapping

---
 README.rst              |  4 ++
 fiber_orm.nimble        |  1 +
 src/fiber_orm/util.nim  |  7 ++--
 tests/test_distinct.nim | 84 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 92 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_distinct.nim

diff --git a/README.rst b/README.rst
index 1997a45..b33333f 100644
--- a/README.rst
+++ b/README.rst
@@ -289,6 +289,10 @@ Nim Type         Postgres Type           SQLite Type
 `JsonNode`_      `jsonb`_
 ===============  ======================  =================
 
+Distinct types backed by a supported type are parsed through their backing
+type and then converted to the distinct type. This also applies when the
+distinct type is nested in an `Option`_ or `seq`.
+
 .. [#f1] Note that this implies that all `NULL`-able fields should be typed
          as optional using `Option[fieldType]`. Conversely, any fields with
          non-optional types should also be constrained to be `NOT NULL` in
diff --git a/fiber_orm.nimble b/fiber_orm.nimble
index 482244c..ca55deb 100644
--- a/fiber_orm.nimble
+++ b/fiber_orm.nimble
@@ -18,6 +18,7 @@ requires "namespaced_logging >= 2.0.2"
 
 task unittest, "Runs the unit test suite.":
   exec "nim c -r --path:src tests/test_datetime"
+  exec "nim c -r --path:src tests/test_distinct"
 
 task integrationtest, "Runs the PostgreSQL integration test suite.":
   exec "nim c -r --path:src tests/test_datetime_postgres"
diff --git a/src/fiber_orm/util.nim b/src/fiber_orm/util.nim
index 0a1030e..8b89c7c 100644
--- a/src/fiber_orm/util.nim
+++ b/src/fiber_orm/util.nim
@@ -266,10 +266,9 @@ func createParseStmt*(t, value: NimNode): NimNode =
     else: error "Cannot parse column with unknown generic instance type: " & $t.getTypeInst
 
   elif t.typeKind == ntyDistinct:
-    result = quote do:
-      block:
-        let tmp: `t` = `value`
-        tmp
+    let baseType = t.getTypeImpl[0]
+    let parseStmt = createParseStmt(baseType, value)
+    result = quote do: `t`(`parseStmt`)
 
   elif t.typeKind == ntyRef:
 
diff --git a/tests/test_distinct.nim b/tests/test_distinct.nim
new file mode 100644
index 0000000..f4d4d12
--- /dev/null
+++ b/tests/test_distinct.nim
@@ -0,0 +1,84 @@
+import std/[options, times, unittest]
+
+import uuids
+
+import fiber_orm/util
+
+
+type
+  StringId = distinct string
+  NestedStringId = distinct StringId
+  UuidId = distinct UUID
+  Count = distinct int
+  Ratio = distinct float
+  Enabled = distinct bool
+
+  State = enum
+    pending
+    complete
+
+  DistinctState = distinct State
+
+  DistinctModel = object
+    id: StringId
+    nestedId: NestedStringId
+    userId: UuidId
+    count: Count
+    ratio: Ratio
+    enabled: Enabled
+    state: DistinctState
+    optionalId: Option[StringId]
+    absentId: Option[StringId]
+    relatedIds: seq[StringId]
+    occurredAt: DateTime
+
+
+suite "distinct type row mapping":
+
+  test "parses each distinct type through its backing type":
+    let model = rowToModel(DistinctModel, @[
+      "item_123",
+      "nested_123",
+      "07e268ed-a3c1-4952-bc45-778b3000b76c",
+      "42",
+      "1.25",
+      "true",
+      "complete",
+      "optional_123",
+      "",
+      "{related_1,related_2}",
+      "2026-08-26 14:32:10.123457+00",
+    ])
+
+    check:
+      string(model.id) == "item_123"
+      string(StringId(model.nestedId)) == "nested_123"
+      UUID(model.userId) ==
+        parseUUID("07e268ed-a3c1-4952-bc45-778b3000b76c")
+      int(model.count) == 42
+      float(model.ratio) == 1.25
+      bool(model.enabled)
+      State(model.state) == complete
+      model.optionalId.isSome
+      string(model.optionalId.get) == "optional_123"
+      model.absentId.isNone
+      model.relatedIds.len == 2
+      string(model.relatedIds[0]) == "related_1"
+      string(model.relatedIds[1]) == "related_2"
+      model.occurredAt.nanosecond == 123_457_000
+
+  test "preserves backing-type parse failures":
+    expect ValueError:
+      discard rowToModel(DistinctModel, @[
+        "item_123",
+        "nested_123",
+        "not-a-uuid",
+        "42",
+        "1.25",
+        "true",
+        "complete",
+        "",
+        "",
+        "{}",
+        "2026-08-26 14:32:10+00",
+      ])