From d443b17a8dd159f313e93f13be2e0db86a89fd13 Mon Sep 17 00:00:00 2001
From: spinillos <selenepinillos@gmail.com>
Date: Fri, 31 Mar 2023 15:43:28 +0200
Subject: [PATCH] Fix null types generation

---
 generate_test.go                |  1 -
 generator.go                    | 10 +++++++++-
 testdata/imports/nulltype.txtar |  8 ++++----
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/generate_test.go b/generate_test.go
index 16a3737..a9d2e4d 100644
--- a/generate_test.go
+++ b/generate_test.go
@@ -48,7 +48,6 @@ func TestGenerateWithImports(t *testing.T) {
 			"imports/struct_shorthand": "Shorthand struct notation is currently unsupported, needs fixing",
 			"imports/single_embed":     "Single-item struct embeds should be treated as just another interface to compose, but get confused with references - #60",
 			"imports/inline_comments":  "Inline comments do not appear be retrievable from cue.Value.Doc()",
-			"imports/nulltype":         "null types are not handled correctly",
 		},
 	}
 
diff --git a/generator.go b/generator.go
index 504bb6e..818cd32 100644
--- a/generator.go
+++ b/generator.go
@@ -1226,7 +1226,13 @@ func (g generator) tsprintField(v cue.Value, isType bool) (ts.Expr, error) {
 			return nil, valError(v, "bounds constraints are not supported as they lack a direct typescript equivalent")
 		}
 		fallthrough
-	case cue.FloatKind, cue.IntKind, cue.BoolKind, cue.NullKind, cue.StructKind:
+	case cue.NullKind:
+		// It evaluates single null value
+		if op == cue.NoOp && len(dvals) == 0 {
+			return tsprintType(cue.NullKind), nil
+		}
+		fallthrough
+	case cue.FloatKind, cue.IntKind, cue.BoolKind, cue.StructKind:
 		// Having eliminated the possibility of bounds/constraints, we're left
 		// with disjunctions and basic types.
 		switch op {
@@ -1292,6 +1298,8 @@ func tsprintType(k cue.Kind) ts.Expr {
 		return ts.Ident("number")
 	case cue.TopKind:
 		return ts.Ident("unknown")
+	case cue.NullKind:
+		return ts.Ident("null")
 	default:
 		return nil
 	}
diff --git a/testdata/imports/nulltype.txtar b/testdata/imports/nulltype.txtar
index 656bb7a..14633cf 100644
--- a/testdata/imports/nulltype.txtar
+++ b/testdata/imports/nulltype.txtar
@@ -15,12 +15,12 @@ obj: {
 
 export type nullType = null;
 
-export type nullInUnion = string | null;
+export type nullInUnion = (string | null);
 
-export type nullDefault = "foo" | "bar" | null;
+export type nullDefault = ('foo' | 'bar' | null);
 
 export const defaultnullDefault: nullDefault = null;
 
 export interface obj {
-    nullField: null
-}
\ No newline at end of file
+  nullField: null;
+}