feat (docs): error handling for generateObject (#2281)

content/docs/03-ai-sdk-core/10-generating-structured-data.mdx

@@ -63,9 +63,9 @@ for await (const partialObject of partialObjectStream) {
 
 You can use `streamObject` to stream generated UIs in combination with React Server Components (see [Generative UI](../ai-sdk-rsc))) or the [`useObject`](/docs/reference/ai-sdk-ui/use-object) hook.
 
-## Guide
+## Schema Writing Tips
 
-The mapping from Zod schemas to LLM inputs (typically JSON schema) is not always straightforward.
+The mapping from Zod schemas to LLM inputs (typically JSON schema) is not always straightforward, since the mapping is not one-to-one.
 Please checkout the following tips and the [Prompt Engineering with Tools](/docs/ai-sdk-core/tools-and-tool-calling#prompt-engineering-with-tools) guide.
 
 ### Generating Arrays
@@ -111,3 +111,44 @@ const result = await generateObject({
   prompt: 'Generate a fake user profile for testing.',
 });
 ```
+
+## Error Handling
+
+When you use `generateObject`, errors are thrown when the model fails to generate proper JSON (`JSONParseError`)
+or when the generated JSON does not match the schema (`TypeValidationError`).
+Both error types contain additional information, e.g. the generated text or the invalid value.
+
+You can use this to e.g. design a function that safely process the result object and also returns values in error cases:
+
+```ts
+import { openai } from '@ai-sdk/openai';
+import { JSONParseError, TypeValidationError, generateObject } from 'ai';
+import { z } from 'zod';
+
+async function generateLasagnaRecipe<T>(
+  schema: z.Schema<T>,
+): Promise<
+  | { type: 'success'; object: T }
+  | { type: 'parse-error'; text: string }
+  | { type: 'validation-error'; value: unknown }
+  | { type: 'unknown-error'; error: unknown }
+> {
+  try {
+    const result = await generateObject({
+      model: openai('gpt-4-turbo'),
+      schema,
+      prompt: 'Generate a lasagna recipe.',
+    });
+
+    return { type: 'success', object: result.object };
+  } catch (error) {
+    if (TypeValidationError.isTypeValidationError(error)) {
+      return { type: 'validation-error', value: error.value };
+    } else if (JSONParseError.isJSONParseError(error)) {
+      return { type: 'parse-error', text: error.text };
+    } else {
+      return { type: 'unknown-error', error };
+    }
+  }
+}
+```