app_dart/lib/src/model/ci_yaml/ci_yaml.dart - mirrors/cocoon - Git at Google

 // Copyright 2021 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:convert';

 import 'package:cocoon_service/cocoon_service.dart';
 import 'package:github/github.dart';

 import '../proto/internal/scheduler.pb.dart' as pb;
 import 'target.dart';

 /// This is a wrapper class around S[pb.SchedulerConfig].
 ///
 /// See //CI_YAML.md for high level documentation.
 class CiYaml {
   /// Creates [CiYaml] from a [RepositorySlug], [branch], [pb.SchedulerConfig] and an optional [CiYaml] of tip of tree CiYaml.
   ///
   /// If [totConfig] is passed, the validation will verify no new targets have been added that may temporarily break the LUCI infrastructure (such as new prod or presubmit targets).
   CiYaml({
     required this.slug,
     required this.branch,
     required this.config,
     CiYaml? totConfig,
     bool validate = false,
   }) {
     if (validate) {
       _validate(config, branch, totSchedulerConfig: totConfig?.config);
     }
     // Do not filter bringup targets. They are required for backward compatibility
     // with release candidate branches.
     final Iterable<Target> totTargets = totConfig?._targets ?? <Target>[];
     final List<Target> totEnabledTargets = _filterEnabledTargets(totTargets);
     totTargetNames = totEnabledTargets.map((Target target) => target.value.name).toList();
     totPostsubmitTargetNames =
         totConfig?.postsubmitTargets.map((Target target) => target.value.name).toList() ?? <String>[];
   }

   /// List of target names used to filter target from release candidate branches
   /// that were already removed from main.
   List<String>? totTargetNames;

   /// List of postsubmit target names used to filter target from release candidate branches
   /// that were already removed from main.
   List<String>? totPostsubmitTargetNames;

   /// The underlying protobuf that contains the raw data from .ci.yaml.
   pb.SchedulerConfig config;

   /// The [RepositorySlug] that [config] is from.
   final RepositorySlug slug;

   /// The git branch currently being scheduled against.
   final String branch;

   /// Gets all [Target] that run on presubmit for this config.
   List<Target> get presubmitTargets {
     final Iterable<Target> presubmitTargets =
         _targets.where((Target target) => target.value.presubmit && !target.value.bringup);
     List<Target> enabledTargets = _filterEnabledTargets(presubmitTargets);

     if (enabledTargets.isEmpty) {
       throw Exception('$branch is not enabled for this .ci.yaml.\nAdd it to run tests against this PR.');
     }
     // Filter targets removed from main.
     if (totTargetNames!.isNotEmpty) {
       enabledTargets = filterOutdatedTargets(slug, enabledTargets, totTargetNames);
     }
     return enabledTargets;
   }

   /// Gets all [Target] that run on postsubmit for this config.
   List<Target> get postsubmitTargets {
     final Iterable<Target> postsubmitTargets = _targets.where((Target target) => target.value.postsubmit);

     List<Target> enabledTargets = _filterEnabledTargets(postsubmitTargets);
     // Filter targets removed from main.
     if (totPostsubmitTargetNames!.isNotEmpty) {
       enabledTargets = filterOutdatedTargets(slug, enabledTargets, totPostsubmitTargetNames);
     }
     // filter if release_build true if current branch is a release candidate branch.
     enabledTargets = _filterReleaseBuildTargets(enabledTargets);
     return enabledTargets;
   }

   /// Filters post submit targets to remove targets we do not want backfilled.
   List<Target> get backfillTargets {
     final List<Target> filteredTargets = <Target>[];
     for (Target target in postsubmitTargets) {
       final Map<String, Object> properties = target.getProperties();
       if (!properties.containsKey('backfill') || properties['backfill'] as bool) {
         filteredTargets.add(target);
       }
     }
     return filteredTargets;
   }

   /// Filters targets with release_build = true on release candidate branches.
   List<Target> _filterReleaseBuildTargets(List<Target> targets) {
     final List<Target> results = <Target>[];
     final bool releaseBranch = branch.contains(RegExp('^flutter-'));
     if (!releaseBranch) {
       return targets;
     }
     for (Target target in targets) {
       final Map<String, Object> properties = target.getProperties();
       if (!properties.containsKey('release_build') || !(properties['release_build'] as bool)) {
         if (!target.value.bringup) results.add(target);
       }
     }
     return results;
   }

   /// Filters targets that were removed from main. [slug] is the gihub
   /// slug for branch under test, [targets] is the list of targets from
   /// the branch under test and [totTargetNames] is the list of target
   /// names enabled on the default branch.
   List<Target> filterOutdatedTargets(slug, targets, totTargetNames) {
     final String defaultBranch = Config.defaultBranch(slug);
     return targets
         .where(
           (Target target) =>
               (target.value.enabledBranches.isNotEmpty && !target.value.enabledBranches.contains(defaultBranch)) ||
               totTargetNames!.contains(target.value.name),
         )
         .toList();
   }

   /// Filters [targets] to those that should be started immediately.
   ///
   /// Targets with a dependency are triggered when there dependency pushes a notification that it has finished.
   /// This shouldn't be confused for targets that have the property named dependency, which is used by the
   /// flutter_deps recipe module on LUCI.
   List<Target> getInitialTargets(List<Target> targets) {
     Iterable<Target> initialTargets = targets.where((Target target) => target.value.dependencies.isEmpty).toList();
     if (branch != Config.defaultBranch(slug)) {
       // Filter out bringup targets for release branches
       initialTargets = initialTargets.where((Target target) => !target.value.bringup);
     }

     return initialTargets.toList();
   }

   Iterable<Target> get _targets => config.targets.map(
         (pb.Target target) => Target(
           schedulerConfig: config,
           value: target,
           slug: slug,
         ),
       );

   /// Get an unfiltered list of all [targets] that are found in the ci.yaml file.
   List<Target> get targets => _targets.toList();

   /// Filter [targets] to only those that are expected to run for [branch].
   ///
   /// A [Target] is expected to run if:
   ///   1. [Target.enabledBranches] exists and matches [branch].
   ///   2. Otherwise, [config.enabledBranches] matches [branch].
   List<Target> _filterEnabledTargets(Iterable<Target> targets) {
     final List<Target> filteredTargets = <Target>[];

     // 1. Add targets with local definition
     final Iterable<Target> overrideBranchTargets =
         targets.where((Target target) => target.value.enabledBranches.isNotEmpty);
     final Iterable<Target> enabledTargets = overrideBranchTargets
         .where((Target target) => enabledBranchesMatchesCurrentBranch(target.value.enabledBranches, branch));
     filteredTargets.addAll(enabledTargets);

     // 2. Add targets with global definition (this is the majority of targets)
     if (enabledBranchesMatchesCurrentBranch(config.enabledBranches, branch)) {
       final Iterable<Target> defaultBranchTargets =
           targets.where((Target target) => target.value.enabledBranches.isEmpty);
       filteredTargets.addAll(defaultBranchTargets);
     }

     return filteredTargets;
   }

   /// Whether any of the possible [RegExp] in [enabledBranches] match [branch].
   static bool enabledBranchesMatchesCurrentBranch(List<String> enabledBranches, String branch) {
     final List<String> regexes = <String>[];
     for (String enabledBranch in enabledBranches) {
       // Prefix with start of line and suffix with end of line
       regexes.add('^$enabledBranch\$');
     }
     final String rawRegexp = regexes.join('|');
     final RegExp regexp = RegExp(rawRegexp);

     return regexp.hasMatch(branch);
   }

   /// Validates [pb.SchedulerConfig] extracted from [CiYaml] files.
   ///
   /// A [pb.SchedulerConfig] file is considered good if:
   ///   1. It has at least one [pb.Target] in [pb.SchedulerConfig.targets]
   ///   2. It has at least one [branch] in [pb.SchedulerConfig.enabledBranches]
   ///   3. If a second [pb.SchedulerConfig] is passed in,
   ///   we compare the current list of [pb.Target] inside the current [pb.SchedulerConfig], i.e., [schedulerConfig],
   ///   with the list of [pb.Target] from tip of the tree [pb.SchedulerConfig], i.e., [totSchedulerConfig].
   ///   If a [pb.Target] is indentified as a new target compared to target list from tip of the tree, The new target
   ///   should have its field [pb.Target.bringup] set to true.
   ///   4. no cycle should exist in the dependency graph, as tracked by map [targetGraph]
   ///   5. [pb.Target] should not depend on self
   ///   6. [pb.Target] cannot have more than 1 dependency
   ///   7. [pb.Target] should depend on target that already exist in depedency graph, and already recorded in map [targetGraph]
   void _validate(pb.SchedulerConfig schedulerConfig, String branch, {pb.SchedulerConfig? totSchedulerConfig}) {
     if (schedulerConfig.targets.isEmpty) {
       throw const FormatException('Scheduler config must have at least 1 target');
     }

     if (schedulerConfig.enabledBranches.isEmpty) {
       throw const FormatException('Scheduler config must have at least 1 enabled branch');
     }

     final Map<String, List<pb.Target>> targetGraph = <String, List<pb.Target>>{};
     final List<String> exceptions = <String>[];
     final Set<String> totTargets = <String>{};
     if (totSchedulerConfig != null) {
       for (pb.Target target in totSchedulerConfig.targets) {
         totTargets.add(target.name);
       }
     }
     // Construct [targetGraph]. With a one scan approach, cycles in the graph
     // cannot exist as it only works forward.
     for (final pb.Target target in schedulerConfig.targets) {
       if (targetGraph.containsKey(target.name)) {
         exceptions.add('ERROR: ${target.name} already exists in graph');
       } else {
         // a new build without "bringup: true"
         // link to wiki - https://github.com/flutter/flutter/wiki/Reducing-Test-Flakiness#adding-a-new-devicelab-test
         if (totTargets.isNotEmpty && !totTargets.contains(target.name) && target.bringup != true) {
           exceptions.add(
             'ERROR: ${target.name} is a new builder added. it needs to be marked bringup: true\nIf ci.yaml wasn\'t changed, try `git fetch upstream && git merge upstream/master`',
           );
           continue;
         }
         targetGraph[target.name] = <pb.Target>[];
         // Add edges
         if (target.dependencies.isNotEmpty) {
           if (target.dependencies.length != 1) {
             exceptions
                 .add('ERROR: ${target.name} has multiple dependencies which is not supported. Use only one dependency');
           } else {
             if (target.dependencies.first == target.name) {
               exceptions.add('ERROR: ${target.name} cannot depend on itself');
             } else if (targetGraph.containsKey(target.dependencies.first)) {
               targetGraph[target.dependencies.first]!.add(target);
             } else {
               exceptions.add('ERROR: ${target.name} depends on ${target.dependencies.first} which does not exist');
             }
           }
         }
       }

       /// Check the dependencies for the current target if it is viable and to
       /// be added to graph. Temporarily this is only being done on non-release
       /// branches.
       if (branch == Config.defaultBranch(slug)) {
         final String? dependencyJson = target.properties['dependencies'];
         if (dependencyJson != null) {
           DependencyValidator.hasVersion(dependencyJsonString: dependencyJson);
         }
       }
     }
     _checkExceptions(exceptions);
   }

   void _checkExceptions(List<String> exceptions) {
     if (exceptions.isNotEmpty) {
       final String fullException = exceptions.reduce((String exception, _) => '$exception\n');
       throw FormatException(fullException);
     }
   }
 }

 /// Class to verify the version of the dependencies in the ci.yaml config file
 /// for each target we are going to execute.
 class DependencyValidator {
   /// dependencyJsonString is guaranteed to be non empty as it must be found
   /// before this method is called.
   ///
   /// Checks a dependency string for a pinned version.
   /// If a version is found then it must not be empty or 'latest.'
   static void hasVersion({required String dependencyJsonString}) {
     final List<String> exceptions = <String>[];

     /// Decoded will contain a list of maps for the dependencies found.
     final List<dynamic> decoded = json.decode(dependencyJsonString) as List<dynamic>;

     for (Map<String, dynamic> depMap in decoded) {
       if (!depMap.containsKey('version')) {
         exceptions.add('ERROR: dependency ${depMap['dependency']} must have a version.');
       } else {
         final String version = depMap['version'] as String;
         if (version.isEmpty || version == 'latest') {
           exceptions
               .add('ERROR: dependency ${depMap['dependency']} must have a non empty, non "latest" version supplied.');
         }
       }
     }

     if (exceptions.isNotEmpty) {
       final String fullException = exceptions.reduce((String exception, _) => '$exception\n');
       throw FormatException(fullException);
     }
   }
 }
	// Copyright 2021 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:convert';

	import 'package:cocoon_service/cocoon_service.dart';
	import 'package:github/github.dart';

	import '../proto/internal/scheduler.pb.dart' as pb;
	import 'target.dart';

	/// This is a wrapper class around S[pb.SchedulerConfig].
	///
	/// See //CI_YAML.md for high level documentation.
	class CiYaml {
	/// Creates [CiYaml] from a [RepositorySlug], [branch], [pb.SchedulerConfig] and an optional [CiYaml] of tip of tree CiYaml.
	///
	/// If [totConfig] is passed, the validation will verify no new targets have been added that may temporarily break the LUCI infrastructure (such as new prod or presubmit targets).
	CiYaml({
	required this.slug,
	required this.branch,
	required this.config,
	CiYaml? totConfig,
	bool validate = false,
	}) {
	if (validate) {
	_validate(config, branch, totSchedulerConfig: totConfig?.config);
	}
	// Do not filter bringup targets. They are required for backward compatibility
	// with release candidate branches.
	final Iterable<Target> totTargets = totConfig?._targets ?? <Target>[];
	final List<Target> totEnabledTargets = _filterEnabledTargets(totTargets);
	totTargetNames = totEnabledTargets.map((Target target) => target.value.name).toList();
	totPostsubmitTargetNames =
	totConfig?.postsubmitTargets.map((Target target) => target.value.name).toList() ?? <String>[];
	}

	/// List of target names used to filter target from release candidate branches
	/// that were already removed from main.
	List<String>? totTargetNames;

	/// List of postsubmit target names used to filter target from release candidate branches
	/// that were already removed from main.
	List<String>? totPostsubmitTargetNames;

	/// The underlying protobuf that contains the raw data from .ci.yaml.
	pb.SchedulerConfig config;

	/// The [RepositorySlug] that [config] is from.
	final RepositorySlug slug;

	/// The git branch currently being scheduled against.
	final String branch;

	/// Gets all [Target] that run on presubmit for this config.
	List<Target> get presubmitTargets {
	final Iterable<Target> presubmitTargets =
	_targets.where((Target target) => target.value.presubmit && !target.value.bringup);
	List<Target> enabledTargets = _filterEnabledTargets(presubmitTargets);

	if (enabledTargets.isEmpty) {
	throw Exception('$branch is not enabled for this .ci.yaml.\nAdd it to run tests against this PR.');
	}
	// Filter targets removed from main.
	if (totTargetNames!.isNotEmpty) {
	enabledTargets = filterOutdatedTargets(slug, enabledTargets, totTargetNames);
	}
	return enabledTargets;
	}

	/// Gets all [Target] that run on postsubmit for this config.
	List<Target> get postsubmitTargets {
	final Iterable<Target> postsubmitTargets = _targets.where((Target target) => target.value.postsubmit);

	List<Target> enabledTargets = _filterEnabledTargets(postsubmitTargets);
	// Filter targets removed from main.
	if (totPostsubmitTargetNames!.isNotEmpty) {
	enabledTargets = filterOutdatedTargets(slug, enabledTargets, totPostsubmitTargetNames);
	}
	// filter if release_build true if current branch is a release candidate branch.
	enabledTargets = _filterReleaseBuildTargets(enabledTargets);
	return enabledTargets;
	}

	/// Filters post submit targets to remove targets we do not want backfilled.
	List<Target> get backfillTargets {
	final List<Target> filteredTargets = <Target>[];
	for (Target target in postsubmitTargets) {
	final Map<String, Object> properties = target.getProperties();
	if (!properties.containsKey('backfill') \|\| properties['backfill'] as bool) {
	filteredTargets.add(target);
	}
	}
	return filteredTargets;
	}

	/// Filters targets with release_build = true on release candidate branches.
	List<Target> _filterReleaseBuildTargets(List<Target> targets) {
	final List<Target> results = <Target>[];
	final bool releaseBranch = branch.contains(RegExp('^flutter-'));
	if (!releaseBranch) {
	return targets;
	}
	for (Target target in targets) {
	final Map<String, Object> properties = target.getProperties();
	if (!properties.containsKey('release_build') \|\| !(properties['release_build'] as bool)) {
	if (!target.value.bringup) results.add(target);
	}
	}
	return results;
	}

	/// Filters targets that were removed from main. [slug] is the gihub
	/// slug for branch under test, [targets] is the list of targets from
	/// the branch under test and [totTargetNames] is the list of target
	/// names enabled on the default branch.
	List<Target> filterOutdatedTargets(slug, targets, totTargetNames) {
	final String defaultBranch = Config.defaultBranch(slug);
	return targets
	.where(
	(Target target) =>
	(target.value.enabledBranches.isNotEmpty && !target.value.enabledBranches.contains(defaultBranch)) \|\|
	totTargetNames!.contains(target.value.name),
	)
	.toList();
	}

	/// Filters [targets] to those that should be started immediately.
	///
	/// Targets with a dependency are triggered when there dependency pushes a notification that it has finished.
	/// This shouldn't be confused for targets that have the property named dependency, which is used by the
	/// flutter_deps recipe module on LUCI.
	List<Target> getInitialTargets(List<Target> targets) {
	Iterable<Target> initialTargets = targets.where((Target target) => target.value.dependencies.isEmpty).toList();
	if (branch != Config.defaultBranch(slug)) {
	// Filter out bringup targets for release branches
	initialTargets = initialTargets.where((Target target) => !target.value.bringup);
	}

	return initialTargets.toList();
	}

	Iterable<Target> get _targets => config.targets.map(
	(pb.Target target) => Target(
	schedulerConfig: config,
	value: target,
	slug: slug,
	),
	);

	/// Get an unfiltered list of all [targets] that are found in the ci.yaml file.
	List<Target> get targets => _targets.toList();

	/// Filter [targets] to only those that are expected to run for [branch].
	///
	/// A [Target] is expected to run if:
	/// 1. [Target.enabledBranches] exists and matches [branch].
	/// 2. Otherwise, [config.enabledBranches] matches [branch].
	List<Target> _filterEnabledTargets(Iterable<Target> targets) {
	final List<Target> filteredTargets = <Target>[];

	// 1. Add targets with local definition
	final Iterable<Target> overrideBranchTargets =
	targets.where((Target target) => target.value.enabledBranches.isNotEmpty);
	final Iterable<Target> enabledTargets = overrideBranchTargets
	.where((Target target) => enabledBranchesMatchesCurrentBranch(target.value.enabledBranches, branch));
	filteredTargets.addAll(enabledTargets);

	// 2. Add targets with global definition (this is the majority of targets)
	if (enabledBranchesMatchesCurrentBranch(config.enabledBranches, branch)) {
	final Iterable<Target> defaultBranchTargets =
	targets.where((Target target) => target.value.enabledBranches.isEmpty);
	filteredTargets.addAll(defaultBranchTargets);
	}

	return filteredTargets;
	}

	/// Whether any of the possible [RegExp] in [enabledBranches] match [branch].
	static bool enabledBranchesMatchesCurrentBranch(List<String> enabledBranches, String branch) {
	final List<String> regexes = <String>[];
	for (String enabledBranch in enabledBranches) {
	// Prefix with start of line and suffix with end of line
	regexes.add('^$enabledBranch\$');
	}
	final String rawRegexp = regexes.join('\|');
	final RegExp regexp = RegExp(rawRegexp);

	return regexp.hasMatch(branch);
	}

	/// Validates [pb.SchedulerConfig] extracted from [CiYaml] files.
	///
	/// A [pb.SchedulerConfig] file is considered good if:
	/// 1. It has at least one [pb.Target] in [pb.SchedulerConfig.targets]
	/// 2. It has at least one [branch] in [pb.SchedulerConfig.enabledBranches]
	/// 3. If a second [pb.SchedulerConfig] is passed in,
	/// we compare the current list of [pb.Target] inside the current [pb.SchedulerConfig], i.e., [schedulerConfig],
	/// with the list of [pb.Target] from tip of the tree [pb.SchedulerConfig], i.e., [totSchedulerConfig].
	/// If a [pb.Target] is indentified as a new target compared to target list from tip of the tree, The new target
	/// should have its field [pb.Target.bringup] set to true.
	/// 4. no cycle should exist in the dependency graph, as tracked by map [targetGraph]
	/// 5. [pb.Target] should not depend on self
	/// 6. [pb.Target] cannot have more than 1 dependency
	/// 7. [pb.Target] should depend on target that already exist in depedency graph, and already recorded in map [targetGraph]
	void _validate(pb.SchedulerConfig schedulerConfig, String branch, {pb.SchedulerConfig? totSchedulerConfig}) {
	if (schedulerConfig.targets.isEmpty) {
	throw const FormatException('Scheduler config must have at least 1 target');
	}

	if (schedulerConfig.enabledBranches.isEmpty) {
	throw const FormatException('Scheduler config must have at least 1 enabled branch');
	}

	final Map<String, List<pb.Target>> targetGraph = <String, List<pb.Target>>{};
	final List<String> exceptions = <String>[];
	final Set<String> totTargets = <String>{};
	if (totSchedulerConfig != null) {
	for (pb.Target target in totSchedulerConfig.targets) {
	totTargets.add(target.name);
	}
	}
	// Construct [targetGraph]. With a one scan approach, cycles in the graph
	// cannot exist as it only works forward.
	for (final pb.Target target in schedulerConfig.targets) {
	if (targetGraph.containsKey(target.name)) {
	exceptions.add('ERROR: ${target.name} already exists in graph');
	} else {
	// a new build without "bringup: true"
	// link to wiki - https://github.com/flutter/flutter/wiki/Reducing-Test-Flakiness#adding-a-new-devicelab-test
	if (totTargets.isNotEmpty && !totTargets.contains(target.name) && target.bringup != true) {
	exceptions.add(
	'ERROR: ${target.name} is a new builder added. it needs to be marked bringup: true\nIf ci.yaml wasn\'t changed, try `git fetch upstream && git merge upstream/master`',
	);
	continue;
	}
	targetGraph[target.name] = <pb.Target>[];
	// Add edges
	if (target.dependencies.isNotEmpty) {
	if (target.dependencies.length != 1) {
	exceptions
	.add('ERROR: ${target.name} has multiple dependencies which is not supported. Use only one dependency');
	} else {
	if (target.dependencies.first == target.name) {
	exceptions.add('ERROR: ${target.name} cannot depend on itself');
	} else if (targetGraph.containsKey(target.dependencies.first)) {
	targetGraph[target.dependencies.first]!.add(target);
	} else {
	exceptions.add('ERROR: ${target.name} depends on ${target.dependencies.first} which does not exist');
	}
	}
	}
	}

	/// Check the dependencies for the current target if it is viable and to
	/// be added to graph. Temporarily this is only being done on non-release
	/// branches.
	if (branch == Config.defaultBranch(slug)) {
	final String? dependencyJson = target.properties['dependencies'];
	if (dependencyJson != null) {
	DependencyValidator.hasVersion(dependencyJsonString: dependencyJson);
	}
	}
	}
	_checkExceptions(exceptions);
	}

	void _checkExceptions(List<String> exceptions) {
	if (exceptions.isNotEmpty) {
	final String fullException = exceptions.reduce((String exception, _) => '$exception\n');
	throw FormatException(fullException);
	}
	}
	}

	/// Class to verify the version of the dependencies in the ci.yaml config file
	/// for each target we are going to execute.
	class DependencyValidator {
	/// dependencyJsonString is guaranteed to be non empty as it must be found
	/// before this method is called.
	///
	/// Checks a dependency string for a pinned version.
	/// If a version is found then it must not be empty or 'latest.'
	static void hasVersion({required String dependencyJsonString}) {
	final List<String> exceptions = <String>[];

	/// Decoded will contain a list of maps for the dependencies found.
	final List<dynamic> decoded = json.decode(dependencyJsonString) as List<dynamic>;

	for (Map<String, dynamic> depMap in decoded) {
	if (!depMap.containsKey('version')) {
	exceptions.add('ERROR: dependency ${depMap['dependency']} must have a version.');
	} else {
	final String version = depMap['version'] as String;
	if (version.isEmpty \|\| version == 'latest') {
	exceptions
	.add('ERROR: dependency ${depMap['dependency']} must have a non empty, non "latest" version supplied.');
	}
	}
	}

	if (exceptions.isNotEmpty) {
	final String fullException = exceptions.reduce((String exception, _) => '$exception\n');
	throw FormatException(fullException);
	}
	}
	}