fix: joi supports string values with null default (#361)

apply fix/tests from
#360 to the joi
schema builder

Author: mnahkies

packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.spec.ts

@@ -625,6 +625,20 @@ describe.each(testVersions)(
 
         await expect(execute(undefined)).resolves.toBe(0)
       })
+
+      it("supports default values of null when nullable", async () => {
+        const {code, execute} = await getActualFromModel({
+          ...base,
+          nullable: true,
+          default: null,
+        })
+
+        expect(code).toMatchInlineSnapshot(
+          `"const x = joi.number().allow(null).default(null)"`,
+        )
+
+        await expect(execute(undefined)).resolves.toBeNull()
+      })
     })
 
     describe("strings", () => {
@@ -766,6 +780,20 @@ describe.each(testVersions)(
         await expect(execute(undefined)).resolves.toBe("example")
       })
 
+      it("supports default values of null when nullable", async () => {
+        const {code, execute} = await getActualFromModel({
+          ...base,
+          nullable: true,
+          default: null,
+        })
+
+        expect(code).toMatchInlineSnapshot(
+          `"const x = joi.string().allow(null).default(null)"`,
+        )
+
+        await expect(execute(undefined)).resolves.toBeNull()
+      })
+
       it("supports empty string default values", async () => {
         const {code, execute} = await getActualFromModel({
           ...base,
@@ -906,6 +934,20 @@ describe.each(testVersions)(
         await expect(execute(undefined)).resolves.toBe(true)
       })
 
+      it("supports default values of null when nullable", async () => {
+        const {code, execute} = await getActualFromModel({
+          ...base,
+          nullable: true,
+          default: null,
+        })
+
+        expect(code).toMatchInlineSnapshot(
+          `"const x = joi.boolean().truthy(1, "1").falsy(0, "0").allow(null).default(null)"`,
+        )
+
+        await expect(execute(undefined)).resolves.toBeNull()
+      })
+
       it("support enum of 'true'", async () => {
         const {code, execute} = await getActualFromModel({
           ...base,

packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.ts

@@ -313,7 +313,10 @@ export class JoiBuilder extends AbstractSchemaBuilder<
     // for stuff like this, eg: https://github.com/github/rest-api-description/issues/3878
     // lets coerce defaults to be strings when the model type is expecting that.
     const needsWrapping =
-      model.type === "string" && typeof model.default !== "string"
+      model.type === "string" &&
+      typeof model.default !== "string" &&
+      !(model.nullable && model.default === null)
+
     const defaultValue = JSON.stringify(model.default)
 
     return [