fix: validate missing dependencies and refactor SummaryReader to nullable

package/inject_compile_generator/CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 0.9.2
-- Throw StateError on circular dependency detection instead of logging a warning to a detached logger.
+- Throw StateError on circular dependency cycles instead of logging a warning.
+- Add compile-time validation for missing dependency providers to fail the build runner step early with a descriptive error message.
+- Refactor `SummaryReader` API to return nullable summaries instead of throwing `FileSystemException`, avoiding control-flow exceptions.
 
 ## 0.9.1
 - Add example/example.md file

package/inject_compile_generator/lib/src/graph/injector_graph_resolver.dart

@@ -21,6 +21,11 @@ class InjectorGraphResolver {
     final allModules = <ModuleSummary>[];
     final providersByModules = <LookupKey, DependencyProvidedByModule>{};
     final injectables = <LookupKey, InjectableSummary>{};
+    final requestedByMap = <LookupKey, Set<SymbolPath>>{};
+
+    void recordRequest(LookupKey key, SymbolPath requestedBy) {
+      requestedByMap.putIfAbsent(key, () => {}).add(requestedBy);
+    }
 
     // 1. Collect all modules starting from the injector.
     for (final modulePath in _injectorSummary.modules) {
@@ -32,6 +37,8 @@ class InjectorGraphResolver {
       LookupKey key, {
       required SymbolPath requestedBy,
     }) async {
+      recordRequest(key, requestedBy);
+
       // Modules take precedence.
       if (providersByModules.containsKey(key) || injectables.containsKey(key)) {
         return;
@@ -41,13 +48,15 @@ class InjectorGraphResolver {
         final summary = await _reader.read(
           AssetId(key.root.package!, key.root.path!),
         );
-        for (final injectable in summary.injectables) {
-          if (injectable.clazz == key.root) {
-            injectables[key] = injectable;
-            for (final dep in injectable.constructor.dependencies) {
-              await resolveKey(dep.lookupKey, requestedBy: injectable.clazz);
+        if (summary != null) {
+          for (final injectable in summary.injectables) {
+            if (injectable.clazz == key.root) {
+              injectables[key] = injectable;
+              for (final dep in injectable.constructor.dependencies) {
+                await resolveKey(dep.lookupKey, requestedBy: injectable.clazz);
+              }
+              return;
             }
-            return;
           }
         }
       }
@@ -70,6 +79,27 @@ class InjectorGraphResolver {
       );
     }
 
+    // Check for missing dependency providers.
+    final missingDependencies = <LookupKey, Set<SymbolPath>>{};
+    for (final key in requestedByMap.keys) {
+      if (!providersByModules.containsKey(key) &&
+          !injectables.containsKey(key)) {
+        missingDependencies[key] = requestedByMap[key]!;
+      }
+    }
+
+    if (missingDependencies.isNotEmpty) {
+      final message = StringBuffer('Missing dependency providers:\n');
+      missingDependencies.forEach((key, requesters) {
+        message.writeln('  - ${key.toPrettyString()}');
+        message.writeln('    requested by:');
+        for (final req in requesters) {
+          message.writeln('      * ${req.symbol} (${req.toAbsoluteUri()})');
+        }
+      });
+      throw StateError(message.toString());
+    }
+
     // 3. Construct the merged dependencies map.
     final mergedDependencies = <LookupKey, ResolvedDependency>{};
     injectables.forEach((key, summary) {
@@ -106,6 +136,10 @@ class InjectorGraphResolver {
     final summary = await _reader.read(
       AssetId(modulePath.package!, modulePath.path!),
     );
+    if (summary == null) {
+      _logger.severe('Module summary not found for $modulePath.');
+      return;
+    }
     final module = summary.modules.firstWhereOrNull(
       (m) => m.clazz == modulePath,
     );

package/inject_compile_generator/lib/src/graph/summary_reader.dart

@@ -1,12 +1,11 @@
 import 'dart:convert';
-import 'dart:io';
 import 'package:build/build.dart';
 import '../models/summary.dart';
 
 /// A reader that retrieves and caches [LibrarySummary] instances.
 abstract class SummaryReader {
-  /// The [LibrarySummary] read from [assetId].
-  Future<LibrarySummary> read(AssetId assetId);
+  /// The [LibrarySummary] read from [assetId], or null if the summary does not exist.
+  Future<LibrarySummary?> read(AssetId assetId);
 }
 
 /// An implementation of [SummaryReader] that uses an [AssetReader] to load summaries.
@@ -17,7 +16,7 @@ class AssetSummaryReader implements SummaryReader {
   AssetSummaryReader(this._reader);
 
   @override
-  Future<LibrarySummary> read(AssetId assetId) async {
+  Future<LibrarySummary?> read(AssetId assetId) async {
     if (_cache.containsKey(assetId)) {
       return _cache[assetId]!;
     }
@@ -27,10 +26,7 @@ class AssetSummaryReader implements SummaryReader {
     final summaryId = assetId.changeExtension('.inject.summary');
 
     if (!await _reader.canRead(summaryId)) {
-      throw FileSystemException(
-        summaryId.uri.toString(),
-        'Could not read summary file',
-      );
+      return null;
     }
 
     final json = await _reader.readAsString(summaryId);

package/inject_compile_generator/test/graph/injector_graph_resolver_test.dart

@@ -1,4 +1,3 @@
-import 'dart:io';
 import 'package:build/build.dart';
 import 'package:inject_compile_generator/src/graph/injector_graph_resolver.dart';
 import 'package:inject_compile_generator/src/graph/summary_reader.dart';
@@ -141,6 +140,54 @@ void main() {
       final resolver = InjectorGraphResolver(reader, injectorSummary);
       expect(resolver.resolve(), throwsStateError);
     });
+
+    test('fails on missing dependencies', () async {
+      final aPath = SymbolPath(package: 'pkg', path: 'lib/a.dart', symbol: 'A');
+      final bPath = SymbolPath(package: 'pkg', path: 'lib/b.dart', symbol: 'B');
+      final injectorPath = SymbolPath(
+        package: 'pkg',
+        path: 'lib/main.dart',
+        symbol: 'MainInjector',
+      );
+
+      reader.addSummary(
+        AssetId('pkg', 'lib/a.dart'),
+        LibrarySummary(
+          assetUri: 'package:pkg/a.dart',
+          injectables: [
+            InjectableSummary(
+              clazz: aPath,
+              constructor: ProviderSummary(
+                name: '',
+                kind: ProviderKind.constructor,
+                resultType: InjectedType(lookupKey: LookupKey(root: aPath)),
+                isSingleton: false,
+                isAsynchronous: false,
+                dependencies: [InjectedType(lookupKey: LookupKey(root: bPath))],
+              ),
+            ),
+          ],
+        ),
+      );
+
+      final injectorSummary = InjectorSummary(
+        clazz: injectorPath,
+        modules: [],
+        providers: [
+          ProviderSummary(
+            name: 'getA',
+            kind: ProviderKind.method,
+            resultType: InjectedType(lookupKey: LookupKey(root: aPath)),
+            isSingleton: false,
+            isAsynchronous: false,
+            dependencies: [],
+          ),
+        ],
+      );
+
+      final resolver = InjectorGraphResolver(reader, injectorSummary);
+      expect(resolver.resolve(), throwsStateError);
+    });
   });
 }
 
@@ -152,11 +199,7 @@ class FakeSummaryReader implements SummaryReader {
   }
 
   @override
-  Future<LibrarySummary> read(AssetId assetId) async {
-    final summary = _summaries[assetId];
-    if (summary == null) {
-      throw FileSystemException(assetId.uri.toString(), 'Summary not found');
-    }
-    return summary;
+  Future<LibrarySummary?> read(AssetId assetId) async {
+    return _summaries[assetId];
   }
 }