Add documentation on Snaps known errors.

snaps-sidebar.js

@@ -63,6 +63,10 @@ const sidebar = {
           type: "doc",
           id: "reference/permissions",
         },
+        {
+          type: "doc",
+          id: "reference/known-errors",
+        },
         {
           type: "category",
           label: "Snaps command line",

snaps/how-to/communicate-errors.md

@@ -0,0 +1,56 @@
+---
+description: Communicate errors from your Snap without crashing it
+sidebar_position: 9
+---
+
+# Communicate errors
+
+The Snaps SDK exposes a set of known errors that can be thrown from your Snap code without crashing
+the Snap.
+See the [Snaps known errors reference](../reference/known-errors.md) for the full list of errors.
+
+## Import and throw errors
+
+To throw these known errors, first import them from the
+[`@metamask/snaps-sdk`](https://github.com/MetaMask/snaps/tree/main/packages/snaps-sdk) package,
+then throw them where needed.
+For example:
+
+```typescript
+import type { OnRpcRequestHandler } from '@metamask/snaps-sdk';
+import { MethodNotFoundError } from '@metamask/snaps-sdk';
+
+export const onRpcRequest: OnRpcRequestHandler = async ({ request }) => {
+  switch (request.method) {
+    case 'hello':
+      return 'Hello World!';
+    default:
+      // Throw a known error to avoid crashing the Snap
+      throw new MethodNotFoundError();
+  }
+};
+```
+
+### Pass data with the error
+
+The error class constructors exported by `@metamask/snaps-sdk` have the following signature:
+
+```typescript
+class SnapJsonRpcError extends SnapError {
+  new (message?: string, data?: Record<string, Json>)
+}
+```
+
+Both parameters are optional.
+If you don't pass `message`, then a pre-determined message is used.
+If you don't pass `data`, then an empty object is passed.
+
+`data` can be any JSON-serializable object.
+
+## Detect known errors in dapps
+
+Known errors are thrown back to the caller as JSON-RPC errors.
+They have a numeric `code`, a `message` string, and a `data` object.
+
+The [Snaps known errors reference](../reference/known-errors.md) lists all the known errors with
+their codes and intended usage.

snaps/reference/entry-points.md

@@ -1,6 +1,5 @@
 ---
 description: See the Snaps entry points reference.
-sidebar_position: 2
 ---
 
 # Snaps entry points

snaps/reference/known-errors.md

@@ -0,0 +1,26 @@
+---
+description: See the Snaps known errors reference
+---
+
+# Snaps known errors
+
+Snaps can [communicate the following errors](../how-to/communicate-errors.md) without crashing the Snap:
+
+| Error                      | What the error indicates                                    | Error code |
+|----------------------------|-------------------------------------------------------------|:----------:|
+| `ChainDisconnectedError`   | The provider is disconnected from the requested chain.      |   `4901`   |
+| `DisconnectedError`        | The provider is disconnected.                               |   `4900`   |
+| `InternalError`            | An internal error has occurred.                             |  `-32603`  |
+| `InvalidInputError`        | The input to a method is invalid.                           |  `-32000`  |
+| `InvalidParamsError`       | The parameters to a method are invalid.                     |  `-32602`  |
+| `InvalidRequestError`      | The request is invalid.                                     |  `-32600`  |
+| `LimitExceededError`       | A limit has been exceeded.                                  |  `-32005`  |
+| `MethodNotFoundError`      | A method does not exist.                                    |  `-32601`  |
+| `MethodNotSupportedError`  | A method is not supported.                                  |  `-32004`  |
+| `ParseError`               | A request is not valid JSON.                                |  `-32700`  |
+| `ResourceNotFoundError`    | A resource does not exist.                                  |  `-32001`  |
+| `ResourceUnavailableError` | A resource is unavailable.                                  |  `-32002`  |
+| `TransactionRejected`      | A transaction has been rejected.                            |  `-32003`  |
+| `UnauthorizedError`        | The requested method/account is not authorized by the user. |   `4100`   |
+| `UnsupportedMethodError`   | The requested method is not supported by the provider.      |   `4200`   |
+| `UserRejectedRequestError` | The user has rejected the request.                          |   `4001`   |

snaps/reference/permissions.md

@@ -1,6 +1,5 @@
 ---
 description: See the Snaps permissions reference.
-sidebar_position: 4
 ---
 
 import Tabs from '@theme/Tabs';

snaps/reference/snaps-api.md

@@ -1,6 +1,5 @@
 ---
 description: See the Snaps API reference.
-sidebar_position: 1
 toc_max_heading_level: 2
 ---
 

src/css/custom.css

@@ -153,3 +153,11 @@ svg {
 .getfeedback-hidden {
   display: none !important;
 }
+
+.markdown {
+  > h1, h2, h3, h4, h5, h6 {
+    > code {
+      font-size: inherit;
+    }
+  }
+}