Show parent pubspecs when a pubspec could not be found. (#4197)

lib/src/package.dart

diff --git a/lib/src/package.dart b/lib/src/package.dart
index 5685679..d7f8642 100644
--- a/lib/src/package.dart
+++ b/lib/src/package.dart
@@ -123,7 +123,7 @@
     }
   }
 
-  /// Loads the package whose root directory is [packageDir].
+  /// Loads the package whose root directory is [dir].
   ///
   /// Will also load the workspace sub-packages of this package (recursively).
   ///
@@ -162,20 +162,29 @@
       withPubspecOverrides: withPubspecOverrides,
       expectedName: expectedName,
     );
-    final workspacePackages = pubspec.workspace
-        .map(
-          (e) => Package.load(
-            p.join(dir, e),
+
+    final workspacePackages = pubspec.workspace.map(
+      (workspacePath) {
+        try {
+          return Package.load(
+            p.join(dir, workspacePath),
             sources,
             loadPubspec: loadPubspec,
             withPubspecOverrides: withPubspecOverrides,
-          ),
-        )
-        .toList();
+          );
+        } on FileException catch (e) {
+          throw FileException(
+            '${e.message}\n'
+            'That was included in the workspace of ${p.join(dir, 'pubspec.yaml')}.',
+            e.path,
+          );
+        }
+      },
+    ).toList();
     for (final package in workspacePackages) {
       if (package.pubspec.resolution != Resolution.workspace) {
         fail('''
-${package.pubspecPath} is inluded in the workspace from ${p.join(dir, 'pubspec.yaml')}, but does not have `resolution: workspace`.
+${package.pubspecPath} is included in the workspace from ${p.join(dir, 'pubspec.yaml')}, but does not have `resolution: workspace`.
 
 See $workspacesDocUrl for more information.
 ''');

test/workspace_test.dart

diff --git a/test/workspace_test.dart b/test/workspace_test.dart
index 0ff5d4b..7bf8638 100644
--- a/test/workspace_test.dart
+++ b/test/workspace_test.dart
@@ -296,7 +296,7 @@
     await pubGet(
       environment: {'_PUB_TEST_SDK_VERSION': '3.7.0'},
       error: contains(
-        'pkgs${s}a${s}pubspec.yaml is inluded in the workspace from .${s}pubspec.yaml, but does not have `resolution: workspace`.',
+        'pkgs${s}a${s}pubspec.yaml is included in the workspace from .${s}pubspec.yaml, but does not have `resolution: workspace`.',
       ),
     );
   });
@@ -355,6 +355,38 @@
     );
   });
 
+  test('reports missing pubspec.yaml of workspace member correctly', () async {
+    await dir(appPath, [
+      libPubspec(
+        'myapp',
+        '1.2.3',
+        extras: {
+          'workspace': ['a'],
+        },
+        sdk: '^3.7.0',
+      ),
+      dir('a', [
+        libPubspec(
+          'a',
+          '1.0.0',
+          resolutionWorkspace: true,
+          extras: {
+            'workspace': ['b'], // Doesn't exist.
+          },
+        ),
+      ]),
+    ]).create();
+    await pubGet(
+      environment: {'_PUB_TEST_SDK_VERSION': '3.7.0'},
+      error: contains(
+        'Could not find a file named "pubspec.yaml" in "${p.join(sandbox, appPath, 'a', 'b')}".\n'
+        'That was included in the workspace of ${p.join('.', 'a', 'pubspec.yaml')}.\n'
+        'That was included in the workspace of ${p.join('.', 'pubspec.yaml')}.',
+      ),
+      exitCode: NO_INPUT,
+    );
+  });
+
   test('`pub deps` lists dependencies for all members of workspace', () async {
     final server = await servePackages();
     server.serve(