Fix ctx.addIssue in transform to work correctly with parseAsync (#1129)

* Fix transform ctx.addIssue to work with parseAsync

* Add documentation about transform taking ctx

README.md

@@ -1605,7 +1605,28 @@ const stringToNumber = z.string().transform((val) => myString.length);
 stringToNumber.parse("string"); // => 6
 ```
 
-> ⚠️ Transform functions must not throw. Make sure to use refinements before the transform to make sure the input can be parsed by the transform.
+> ⚠️ Transform functions must not throw. Make sure to use refinements before the transform or addIssue within the transform to make sure the input can be parsed by the transform.
+
+#### Validating during transform
+
+Similar to `superRefine`, `transform` can optionally take a `ctx`. This allows you to simultaneously
+validate and transform the value, which can be simpler than chaining `refine` and `validate`. 
+When calling `ctx.addIssue` make sure to still return a value of the correct type otherwise the inferred type will include `undefined`.
+
+```ts
+const Strings = z
+  .string()
+  .transform((val, ctx) => {
+    const parsed = parseInt(val);
+    if (isNaN(parsed)) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: "Not a number",
+      });
+    }
+    return parsed;
+  });
+```
 
 #### Chaining order
 

deno/lib/__tests__/transformer.test.ts

@@ -11,7 +11,7 @@ const stringToNumber = z.string().transform((arg) => parseFloat(arg));
 //   .transform((n) => String(n));
 const asyncNumberToString = z.number().transform(async (n) => String(n));
 
-test("transform ctx.addIssue", () => {
+test("transform ctx.addIssue with parse", () => {
   const strs = ["foo", "bar"];
 
   expect(() => {
@@ -42,6 +42,38 @@ test("transform ctx.addIssue", () => {
   );
 });
 
+test("transform ctx.addIssue with parseAsync", async () => {
+  const strs = ["foo", "bar"];
+
+  const result = await z
+    .string()
+    .transform((data, ctx) => {
+      const i = strs.indexOf(data);
+      if (i === -1) {
+        ctx.addIssue({
+          code: "custom",
+          message: `${data} is not one of our allowed strings`,
+        });
+      }
+      return data.length;
+    })
+    .safeParseAsync("asdf");
+
+  expect(JSON.parse(JSON.stringify(result))).toEqual({
+    success: false,
+    error: {
+      issues: [
+        {
+          code: "custom",
+          message: "asdf is not one of our allowed strings",
+          path: [],
+        },
+      ],
+      name: "ZodError",
+    },
+  });
+});
+
 test("basic transformations", () => {
   const r1 = z
     .string()

deno/lib/types.ts

@@ -3328,7 +3328,7 @@ export class ZodEffects<
             //   return { status: "dirty", value: base.value };
             // }
             return Promise.resolve(effect.transform(base.value, checkCtx)).then(
-              OK
+              (result) => ({ status: status.value, value: result })
             );
           });
       }

src/__tests__/transformer.test.ts

@@ -10,7 +10,7 @@ const stringToNumber = z.string().transform((arg) => parseFloat(arg));
 //   .transform((n) => String(n));
 const asyncNumberToString = z.number().transform(async (n) => String(n));
 
-test("transform ctx.addIssue", () => {
+test("transform ctx.addIssue with parse", () => {
   const strs = ["foo", "bar"];
 
   expect(() => {
@@ -41,6 +41,38 @@ test("transform ctx.addIssue", () => {
   );
 });
 
+test("transform ctx.addIssue with parseAsync", async () => {
+  const strs = ["foo", "bar"];
+
+  const result = await z
+    .string()
+    .transform((data, ctx) => {
+      const i = strs.indexOf(data);
+      if (i === -1) {
+        ctx.addIssue({
+          code: "custom",
+          message: `${data} is not one of our allowed strings`,
+        });
+      }
+      return data.length;
+    })
+    .safeParseAsync("asdf");
+
+  expect(JSON.parse(JSON.stringify(result))).toEqual({
+    success: false,
+    error: {
+      issues: [
+        {
+          code: "custom",
+          message: "asdf is not one of our allowed strings",
+          path: [],
+        },
+      ],
+      name: "ZodError",
+    },
+  });
+});
+
 test("basic transformations", () => {
   const r1 = z
     .string()

src/types.ts

@@ -3328,7 +3328,7 @@ export class ZodEffects<
             //   return { status: "dirty", value: base.value };
             // }
             return Promise.resolve(effect.transform(base.value, checkCtx)).then(
-              OK
+              (result) => ({ status: status.value, value: result })
             );
           });
       }