fix: Run examples from own directory (#834)

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## Description

Due to dart-lang/pub#4486 examples must run
`exec` from their own directories (not sure why this wasn't the case
from the beginning).

## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [ ] ✨ `feat` -- New feature (non-breaking change which adds
functionality)
- [x] 🛠️ `fix` -- Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ `!` -- Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 `refactor` -- Code refactor
- [ ] ✅ `ci` -- Build configuration change
- [ ] 📝 `docs` -- Documentation
- [ ] 🗑️ `chore` -- Chore

docs/environment-variables.mdx

@@ -35,18 +35,18 @@ The path of the package that's currently executing a script (when using
 
 ### `MELOS_PARENT_PACKAGE_NAME`
 
-The name of the parent package of the current package that's currently executing
-a script (when using `melos exec`).
+The name of the parent package of the example that's currently being executed
+in a script (when using `melos exec`).
 
 ### `MELOS_PARENT_PACKAGE_VERSION`
 
-The version of the parent package of the current package that's currently
-executing a script (when using `melos exec`).
+The version of the parent package of the example that's currently being executed
+in a script (when using `melos exec`).
 
 ### `MELOS_PARENT_PACKAGE_PATH`
 
-The path of the parent package of the current package that's currently executing
-a script (when using `melos exec`).
+The path of the parent package of the example that's currently being executed
+in a script (when using `melos exec`).
 
 ### `MELOS_PUBLISH_DRY_RUN`
 
@@ -55,13 +55,14 @@ Whether the current publish is a dry run or not. This is `true` when running
 
 #### What is a 'parent package'
 
-If a package exists in a directory that is also a child of another package, then
-its parent is the 'parent package'. For example; the package `firebase_auth` has
-a `example` directory that is also a package, when running a `melos exec` script
-in the `example` package then the parent package would be `firebase_auth`.
+If an example package exists in a directory that is a child of another package,
+then its parent is the 'parent package'. For example; the package
+`firebase_auth` has an `example` directory that is also a package, when running
+a `melos exec` script in the `example` package then the parent package would be
+`firebase_auth`.
 
 Note, this 'parent package' functionality only currently works when the 'child
-package' name ends with `example`
+package' name ends with `example`.
 
 ## User Defined
 

packages/melos/lib/src/commands/exec.dart

@@ -78,7 +78,7 @@ mixin _ExecMixin on _Melos {
       logger: logger,
       environment: environment,
       workingDirectory: package.path,
-      prefix: prefixLogs ? packagePrefix : null,
+      logPrefix: prefixLogs ? packagePrefix : null,
       // The parent env is injected manually above
       includeParentEnvironment: false,
     );

packages/melos/lib/src/commands/format.dart

@@ -134,7 +134,7 @@ mixin _FormatMixin on _Melos {
       logger: logger,
       environment: environment,
       workingDirectory: package.path,
-      prefix: prefixLogs ? packagePrefix : null,
+      logPrefix: prefixLogs ? packagePrefix : null,
     );
   }
 }

packages/melos/lib/src/common/utils.dart

@@ -440,7 +440,7 @@ List<int> get runningPids => UnmodifiableListView(_runningPids);
 
 Future<int> startCommand(
   List<String> command, {
-  String? prefix,
+  String? logPrefix,
   Map<String, String> environment = const {},
   String? workingDirectory,
   bool onlyOutputOnError = false,
@@ -466,14 +466,14 @@ Future<int> startCommand(
   var stdoutStream = process.stdout;
   var stderrStream = process.stderr;
 
-  if (prefix != null && prefix.isNotEmpty) {
+  if (logPrefix != null && logPrefix.isNotEmpty) {
     final pluginPrefixTransformer =
         StreamTransformer<String, String>.fromHandlers(
       handleData: (data, sink) {
         const lineSplitter = LineSplitter();
         var lines = lineSplitter.convert(data);
         lines = lines
-            .map((line) => '$prefix$line${line.contains('\n') ? '' : '\n'}')
+            .map((line) => '$logPrefix$line${line.contains('\n') ? '' : '\n'}')
             .toList();
         sink.add(lines.join());
       },

packages/melos/lib/src/package.dart

@@ -987,29 +987,8 @@ class Package {
     return pubClient.fetchPackage(name);
   }
 
-  /// The example [Package] contained within this package, if any.
-  ///
-  /// A package is considered to be an example if it is located in the `example`
-  /// directory of the [enclosingPackage].
-  late final Package? examplePackage = () {
-    final examplePath = p.join(path, 'example');
-    return _packageMap.values
-        .firstWhereOrNull((package) => p.equals(package.path, examplePath));
-  }();
-
-  /// The [Package] that encloses this package, if any.
-  ///
-  /// A package is considered to be the enclosing package if this package is
-  /// located in a direct child directory of the enclosing package.
-  late final Package? enclosingPackage = () {
-    final enclosingPackagePath = p.dirname(path);
-    return _packageMap.values.firstWhereOrNull(
-      (package) => p.equals(package.path, enclosingPackagePath),
-    );
-  }();
-
-  /// Whether this package is an example package as defined by [examplePackage].
-  bool get isExample => enclosingPackage?.examplePackage == this;
+  /// Whether this package is an example package.
+  bool get isExample => p.dirname(path).endsWith('example');
 
   /// Returns whether this package is a Flutter app.
   ///