Optimize single-member unions to use literal directly

Copilot · mrlubos · Copilot · commit 707cb1a19c44 · 2025-09-29T19:40:38.000Z
Co-authored-by: mrlubos &lt;12529395+mrlubos@users.noreply.github.com&gt;
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/mini/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/v3/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/2.0.x/v4/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/mini/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
@@ -779,9 +777,7 @@ export const zModelWithConst = z.object({
     String: z.optional(z.enum([
         'String'
     ])),
-    number: z.optional(z.union([
-        z.literal(0)
-    ])),
+    number: z.optional(z.literal(0)),
     null: z.optional(z.unknown()),
     withType: z.optional(z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/v3/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
@@ -777,9 +775,7 @@ export const zModelWithConst = z.object({
     String: z.enum([
         'String'
     ]).optional(),
-    number: z.union([
-        z.literal(0)
-    ]).optional(),
+    number: z.literal(0).optional(),
     null: z.unknown().optional(),
     withType: z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.0.x/v4/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
@@ -779,9 +777,7 @@ export const zModelWithConst = z.object({
     String: z.optional(z.enum([
         'String'
     ])),
-    number: z.optional(z.union([
-        z.literal(0)
-    ])),
+    number: z.optional(z.literal(0)),
     null: z.optional(z.unknown()),
     withType: z.optional(z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/mini/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/v3/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v3/__snapshots__/3.1.x/v4/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/mini/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/v3/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/2.0.x/v4/default/zod.gen.ts
@@ -254,9 +254,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/mini/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
@@ -779,9 +777,7 @@ export const zModelWithConst = z.object({
     String: z.optional(z.enum([
         'String'
     ])),
-    number: z.optional(z.union([
-        z.literal(0)
-    ])),
+    number: z.optional(z.literal(0)),
     null: z.optional(z.unknown()),
     withType: z.optional(z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/v3/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
@@ -777,9 +775,7 @@ export const zModelWithConst = z.object({
     String: z.enum([
         'String'
     ]).optional(),
-    number: z.union([
-        z.literal(0)
-    ]).optional(),
+    number: z.literal(0).optional(),
     null: z.unknown().optional(),
     withType: z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.0.x/v4/default/zod.gen.ts
@@ -336,9 +336,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
@@ -779,9 +777,7 @@ export const zModelWithConst = z.object({
     String: z.optional(z.enum([
         'String'
     ])),
-    number: z.optional(z.union([
-        z.literal(0)
-    ])),
+    number: z.optional(z.literal(0)),
     null: z.optional(z.unknown()),
     withType: z.optional(z.enum([
         'Some string'
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/mini/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/mini/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/v3/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/v3/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ]).optional(),
-    bool: z.union([
-        z.literal(true)
-    ]).optional()
+    bool: z.literal(true).optional()
 });
 
 /**
diff --git a/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/v4/default/zod.gen.ts b/packages/openapi-ts-tests/zod/v4/__snapshots__/3.1.x/v4/default/zod.gen.ts
@@ -345,9 +345,7 @@ export const zModelWithEnum = z.object({
         '500 foo.bar',
         '600 foo&bar'
     ])),
-    bool: z.optional(z.union([
-        z.literal(true)
-    ]))
+    bool: z.optional(z.literal(true))
 });
 
 /**
diff --git a/packages/openapi-ts/src/plugins/zod/mini/plugin.ts b/packages/openapi-ts/src/plugins/zod/mini/plugin.ts
@@ -271,6 +271,9 @@ const enumTypeToZodSchema = ({
         }),
       ],
     });
+  } else if (literalMembers.length === 1) {
+    // For single-member unions, use the member directly instead of wrapping in z.union()
+    result.expression = literalMembers[0];
   } else {
     result.expression = tsc.callExpression({
       functionName: tsc.propertyAccessExpression({
diff --git a/packages/openapi-ts/src/plugins/zod/v3/plugin.ts b/packages/openapi-ts/src/plugins/zod/v3/plugin.ts
@@ -256,6 +256,9 @@ const enumTypeToZodSchema = ({
         }),
       ],
     });
+  } else if (literalMembers.length === 1) {
+    // For single-member unions, use the member directly instead of wrapping in z.union()
+    enumExpression = literalMembers[0];
   } else {
     enumExpression = tsc.callExpression({
       functionName: tsc.propertyAccessExpression({
diff --git a/packages/openapi-ts/src/plugins/zod/v4/plugin.ts b/packages/openapi-ts/src/plugins/zod/v4/plugin.ts
@@ -253,6 +253,9 @@ const enumTypeToZodSchema = ({
         }),
       ],
     });
+  } else if (literalMembers.length === 1) {
+    // For single-member unions, use the member directly instead of wrapping in z.union()
+    result.expression = literalMembers[0];
   } else {
     result.expression = tsc.callExpression({
       functionName: tsc.propertyAccessExpression({
