Add log page

website/docs/essentials/provider_observer.mdx

@@ -0,0 +1,62 @@
+---
+title: Logging and error reporting
+---
+
+import { Link } from "../../src/components/Link";
+import { AutoSnippet, When } from "../../src/components/CodeSnippet";
+import providerObserver from "!!raw-loader!./provider_observer/provider_observer.dart";
+import asyncError from "!!raw-loader!./provider_observer/async_error.dart";
+
+Riverpod natively offers a way to listen to all events happening
+in the provider tree.  
+This can be used to log all the events, or to report errors to a
+remote service.
+
+This is achieved by using the `ProviderObserver` class,
+and passing it to `ProviderScope`/`ProviderContainer`.
+
+## Defining a ProviderObserver
+
+A `ProviderObserver` is a class that should be extended.  
+It offers various methods which can be overridden to listen to events:
+
+- `didAddProvider`, called when a provider is added to the tree
+- `didUpdateProvider`, called when a provider is updated
+- `didDisposeProvider`, called when a provider is disposed
+- `providerDidFail`, when a synchronous provider throws an error
+
+<AutoSnippet raw={providerObserver} />
+
+:::caution
+At the moment, if an error in an asynchronous provider is thrown,
+the error will be received by the `didAddProvider`/`didUpdateProvider` methods
+instead, with an `AsyncError` as value.  
+Note that this will be changed in the version 3.0 of Riverpod.
+
+<AutoSnippet raw={asyncError} />
+
+:::
+
+## Using a ProviderObserver
+
+Now that we've defined an observer, we need to use it.  
+To do so, we should pass it to either `ProviderScope` or `ProviderContainer`:
+
+```dart
+runApp(
+  ProviderScope(
+    observers: [
+      MyObserver(),
+    ],
+    child: MyApp(),
+  )
+);
+```
+
+```dart
+final container = ProviderContainer(
+  observers: [
+    MyObserver(),
+  ],
+);
+```

website/docs/essentials/provider_observer/async_error.dart

@@ -0,0 +1,41 @@
+// ignore_for_file: avoid_print
+
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+/* SNIPPET START */
+class MyObserver extends ProviderObserver {
+  void handleValue(Object? value) {
+    if (value is AsyncError) {
+      print('Error: ${value.error}');
+    }
+  }
+
+  @override
+  void didAddProvider(
+    ProviderBase<Object?> provider,
+    Object? value,
+    ProviderContainer container,
+  ) {
+    handleValue(value);
+  }
+
+  @override
+  void didUpdateProvider(
+    ProviderBase<Object?> provider,
+    Object? previousValue,
+    Object? newValue,
+    ProviderContainer container,
+  ) {
+    handleValue(newValue);
+  }
+
+  @override
+  void providerDidFail(
+    ProviderBase<Object?> provider,
+    Object error,
+    StackTrace stackTrace,
+    ProviderContainer container,
+  ) {
+    print('error: $error');
+  }
+}

website/docs/essentials/provider_observer/provider_observer.dart

@@ -0,0 +1,43 @@
+// ignore_for_file: avoid_print
+
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+/* SNIPPET START */
+class MyObserver extends ProviderObserver {
+  @override
+  void didAddProvider(
+    ProviderBase<Object?> provider,
+    Object? value,
+    ProviderContainer container,
+  ) {
+    print('Provider $provider was initialized with $value');
+  }
+
+  @override
+  void didDisposeProvider(
+    ProviderBase<Object?> provider,
+    ProviderContainer container,
+  ) {
+    print('Provider $provider was disposed');
+  }
+
+  @override
+  void didUpdateProvider(
+    ProviderBase<Object?> provider,
+    Object? previousValue,
+    Object? newValue,
+    ProviderContainer container,
+  ) {
+    print('Provider $provider updated from $previousValue to $newValue');
+  }
+
+  @override
+  void providerDidFail(
+    ProviderBase<Object?> provider,
+    Object error,
+    StackTrace stackTrace,
+    ProviderContainer container,
+  ) {
+    print('Provider $provider threw $error at $stackTrace');
+  }
+}

website/sidebars.js

@@ -33,11 +33,7 @@ module.exports = {
         // },
         "essentials/eager_initialization",
         "essentials/testing",
-        // {
-        //   type: "link",
-        //   label: "Logging and error reporting (WIP)",
-        //   href: "https://github.com/rrousselGit/riverpod/tree/master/examples/marvel",
-        // },
+        "essentials/provider_observer",
         "essentials/faq",
         "essentials/do_dont",
       ],