coverage: Allow specifying coverage flags via a yaml file

pkgs/coverage/bin/collect_coverage.dart

@@ -136,8 +136,8 @@ Options _parseArgs(List<String> arguments, CoverageOptions defaultOptions) {
       (outPath == null && defaultOptions.outputDirectory == null)) {
     out = stdout;
   } else {
-    final outFilePath = p.canonicalize(
-        outPath ?? '${defaultOptions.outputDirectory}/coverage.json');
+    final outFilePath = p.normalize(outPath ??
+        p.absolute(defaultOptions.outputDirectory!, 'coverage.json'));
     final outFile = File(outFilePath)..createSync(recursive: true);
     out = outFile.openWrite();
   }

pkgs/coverage/bin/format_coverage.dart

@@ -242,9 +242,8 @@ Environment parseArgs(List<String> arguments, CoverageOptions defaultOptions) {
   if (args['in'] == null && defaultOptions.outputDirectory == null) {
     fail('No input files given.');
   }
-  final inputPath = args['in'] as String? ??
-      '${defaultOptions.outputDirectory}/coverage.json';
-  final input = p.absolute(p.normalize(inputPath));
+  final input = p.normalize((args['in'] as String?) ??
+      p.absolute(defaultOptions.outputDirectory!, 'coverage.json'));
   if (!FileSystemEntity.isDirectorySync(input) &&
       !FileSystemEntity.isFileSync(input)) {
     fail('Provided input "${args["in"]}" is neither a directory nor a file.');
@@ -256,8 +255,8 @@ Environment parseArgs(List<String> arguments, CoverageOptions defaultOptions) {
       (outPath == null && defaultOptions.outputDirectory == null)) {
     output = stdout;
   } else {
-    final outFilePath = p
-        .canonicalize(outPath ?? '${defaultOptions.outputDirectory}/lcov.info');
+    final outFilePath = p.normalize(
+        outPath ?? p.absolute(defaultOptions.outputDirectory!, 'lcov.info'));
     final outfile = File(outFilePath)..createSync(recursive: true);
     output = outfile.openWrite();
   }

pkgs/coverage/lib/src/coverage_options.dart

@@ -14,19 +14,21 @@ class CoverageOptions {
   });
 
   factory CoverageOptions.fromConfig(
-      Config options, CoverageOptions defaultOptions, String optionsFilePath) {
+      Config options, CoverageOptions defaultOptions, String? optionsFilePath) {
     var outputDirectory = options.optionalString('output_directory') ??
         defaultOptions.outputDirectory;
     var packageDirectory = options.optionalString('package_directory') ??
         defaultOptions.packageDirectory;
 
-    if (outputDirectory != null && !path.isAbsolute(outputDirectory)) {
-      outputDirectory = path.canonicalize(
-          path.join(path.dirname(optionsFilePath), outputDirectory));
-    }
-    if (!path.isAbsolute(packageDirectory)) {
-      packageDirectory = path.canonicalize(
-          path.join(path.dirname(optionsFilePath), packageDirectory));
+    if (optionsFilePath != null) {
+      if (outputDirectory != null && !path.isAbsolute(outputDirectory)) {
+        outputDirectory = path.normalize(
+            path.absolute(path.dirname(optionsFilePath), outputDirectory));
+      }
+      if (!path.isAbsolute(packageDirectory)) {
+        packageDirectory = path.normalize(
+            path.absolute(path.dirname(optionsFilePath), packageDirectory));
+      }
     }
 
     return CoverageOptions(
@@ -74,18 +76,19 @@ class CoverageOptionsProvider {
   }
 
   late final CoverageOptions coverageOptions;
-  late final String optionsFilePath;
+  late final String? optionsFilePath;
   static const defaultFilePath = 'coverage_options.yaml';
 
   File? _getOptionsFile(String? filePath) {
     filePath ??= _findOptionsFilePath();
-    if (filePath == null) {
-      throw StateError('Could not find a pubspec.yaml file.');
-    }
 
-    optionsFilePath = path.canonicalize(filePath);
+    optionsFilePath = filePath != null ? path.canonicalize(filePath) : null;
+
+    if (optionsFilePath == null) {
+      return null;
+    }
 
-    final file = File(optionsFilePath);
+    final file = File(optionsFilePath!);
     return file.existsSync() ? file : null;
   }
 

pkgs/coverage/test/test_coverage_options/partial_fields1.yaml

@@ -2,4 +2,4 @@ output-directory: 'custom_coverage'
 scope-output: 
   - 'lib'
   - 'test'
-package-name: 'Custom Dart Package'
+package-name: 'Custom Dart Package'

pkgs/coverage/test/test_coverage_options/partial_fields2.yaml

@@ -5,4 +5,4 @@ branch-coverage: false
 output-directory: 'custom_lcov'
 package-directory: '.'
 test_script: 'custom_test'
-function-coverage: true
+function-coverage: true