diff --git a/pkgs/pubspec_parse/lib/src/dependency.dart b/pkgs/pubspec_parse/lib/src/dependency.dart
index ff052fa64..416fcbaea 100644
--- a/pkgs/pubspec_parse/lib/src/dependency.dart
+++ b/pkgs/pubspec_parse/lib/src/dependency.dart
@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:collection/collection.dart';
 import 'package:json_annotation/json_annotation.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:yaml/yaml.dart';
@@ -46,18 +45,24 @@ Dependency? _fromJson(Object? data, String name) {
   }
 
   if (data is Map) {
-    final matchedKeys = data.keys
-        .cast<String>()
-        .where((key) => key != 'version')
-        .toList();
+    String? matchedKey;
+    String? secondMatchedKey;
+    String? firstUnrecognizedKey;
+    for (final (key as String) in data.keys) {
+      if (key == 'version') continue;
+      if (matchedKey == null) {
+        matchedKey = key;
+      } else {
+        secondMatchedKey ??= key;
+      }
+      if (!_sourceKeys.contains(key)) {
+        firstUnrecognizedKey ??= key;
+      }
+    }
 
-    if (data.isEmpty || (matchedKeys.isEmpty && data.containsKey('version'))) {
+    if (matchedKey == null) {
       return _$HostedDependencyFromJson(data);
     } else {
-      final firstUnrecognizedKey = matchedKeys.firstWhereOrNull(
-        (k) => !_sourceKeys.contains(k),
-      );
-
       return $checkedNew<Dependency>('Dependency', data, () {
         if (firstUnrecognizedKey != null) {
           throw UnrecognizedKeysException(
@@ -66,20 +71,18 @@ Dependency? _fromJson(Object? data, String name) {
             _sourceKeys,
           );
         }
-        if (matchedKeys.length > 1) {
+        if (secondMatchedKey != null) {
           throw CheckedFromJsonException(
             data,
-            matchedKeys[1],
+            secondMatchedKey,
             'Dependency',
             'A dependency may only have one source.',
           );
         }
 
-        final key = matchedKeys.single;
-
-        return switch (key) {
-          'git' => GitDependency.fromData(data[key]),
-          'path' => PathDependency.fromData(data[key]),
+        return switch (matchedKey) {
+          'git' => GitDependency.fromData(data[matchedKey]),
+          'path' => PathDependency.fromData(data[matchedKey]),
           'sdk' => _$SdkDependencyFromJson(data),
           'hosted' => _$HostedDependencyFromJson(
             data,
@@ -125,17 +128,8 @@ class GitDependency extends Dependency {
 
   GitDependency(this.url, {this.ref, this.path});
 
-  factory GitDependency.fromData(Object? data) {
-    if (data is String) {
-      data = {'url': data};
-    }
-
-    if (data is Map) {
-      return _$GitDependencyFromJson(data);
-    }
-
-    throw ArgumentError.value(data, 'git', 'Must be a String or a Map.');
-  }
+  factory GitDependency.fromData(Object? data) =>
+      _$GitDependencyFromJson(_mapOrStringUri(data, 'git'));
 
   @override
   bool operator ==(Object other) =>
@@ -156,34 +150,37 @@ Uri? parseGitUriOrNull(String? value) =>
 
 Uri parseGitUri(String value) => _tryParseScpUri(value) ?? Uri.parse(value);
 
-/// Supports URIs like `[user@]host.xz:path/to/repo.git/`
+/// Parses URIs like `[user@]host.xz:path/to/repo.git/`.
 /// See https://git-scm.com/docs/git-clone#_git_urls_a_id_urls_a
 Uri? _tryParseScpUri(String value) {
-  final colonIndex = value.indexOf(':');
-
-  if (colonIndex < 0) {
-    return null;
-  } else if (colonIndex == value.indexOf('://')) {
-    // If the first colon is part of a scheme, it's not an scp-like URI
-    return null;
-  }
-  final slashIndex = value.indexOf('/');
-
-  if (slashIndex >= 0 && slashIndex < colonIndex) {
-    // Per docs: This syntax is only recognized if there are no slashes before
-    // the first colon. This helps differentiate a local path that contains a
-    // colon. For example the local path foo:bar could be specified as an
-    // absolute path or ./foo:bar to avoid being misinterpreted as an ssh url.
-    return null;
-  }
-
-  final atIndex = value.indexOf('@');
-  if (colonIndex > atIndex) {
-    final user = atIndex >= 0 ? value.substring(0, atIndex) : null;
-    final host = value.substring(atIndex + 1, colonIndex);
-    final path = value.substring(colonIndex + 1);
-    return Uri(scheme: 'ssh', userInfo: user, host: host, path: path);
+  // Find first `:`. Remember `@` before it, reject if `/` before it.
+  const slashChar = 0x2F, colonChar = 0x3A, atChar = 0x40;
+  var atIndex = -1;
+  for (var i = 0; i < value.length; i++) {
+    final char = value.codeUnitAt(i);
+    if (char == slashChar) {
+      // Per docs: This syntax is only recognized if there are no slashes
+      // before the first colon. This helps differentiate a local path that
+      // contains a colon. For example the local path foo:bar could
+      // be specified as an absolute path or ./foo:bar to avoid being
+      // misinterpreted as an SSH URL
+      break;
+    } else if (char == atChar) {
+      atIndex = i;
+    } else if (char == colonChar) {
+      final colonIndex = i;
+
+      // Assume a `://` means it's a real URI scheme and authority,
+      // not an SCP-like URI.
+      if (value.startsWith('//', colonIndex + 1)) return null;
+
+      final user = atIndex >= 0 ? value.substring(0, atIndex) : null;
+      final host = value.substring(atIndex + 1, colonIndex);
+      final path = value.substring(colonIndex + 1);
+      return Uri(scheme: 'ssh', userInfo: user, host: host, path: path);
+    }
   }
+  // No colon in value, or not before a slash.
   return null;
 }
 
@@ -257,17 +254,8 @@ class HostedDetails {
 
   HostedDetails(this.declaredName, this.url);
 
-  factory HostedDetails.fromJson(Object data) {
-    if (data is String) {
-      data = {'url': data};
-    }
-
-    if (data is Map) {
-      return _$HostedDetailsFromJson(data);
-    }
-
-    throw ArgumentError.value(data, 'hosted', 'Must be a Map or String.');
-  }
+  factory HostedDetails.fromJson(Object data) =>
+      _$HostedDetailsFromJson(_mapOrStringUri(data, 'hosted'));
 
   @override
   bool operator ==(Object other) =>
@@ -279,3 +267,18 @@ class HostedDetails {
 
 VersionConstraint _constraintFromString(String? input) =>
     input == null ? VersionConstraint.any : VersionConstraint.parse(input);
+
+/// The `value` if it is a `Map`, or `{'uri': value}` if it is a `String`.
+///
+/// Must be one or the other.
+/// The [name] is used as parameter name in the thrown error.
+Map _mapOrStringUri(Object? value, String name) {
+  if (value is! Map) {
+    if (value is String) {
+      value = {'url': value};
+    } else {
+      throw ArgumentError.value(value, name, 'Must be a String or a Map.');
+    }
+  }
+  return value;
+}
diff --git a/pkgs/pubspec_parse/lib/src/pubspec.dart b/pkgs/pubspec_parse/lib/src/pubspec.dart
index 01327f4a3..776b33b45 100644
--- a/pkgs/pubspec_parse/lib/src/pubspec.dart
+++ b/pkgs/pubspec_parse/lib/src/pubspec.dart
@@ -60,7 +60,7 @@ class Pubspec {
   @Deprecated('See https://dart.dev/tools/pub/pubspec#authorauthors')
   String? get author {
     if (authors.length == 1) {
-      return authors.single;
+      return authors.first;
     }
     return null;
   }
@@ -140,9 +140,9 @@ class Pubspec {
       throw ArgumentError.value(name, 'name', '"name" cannot be empty.');
     }
 
-    if (publishTo != null && publishTo != 'none') {
+    if (publishTo case final publishTo? when publishTo != 'none') {
       try {
-        final targetUri = Uri.parse(publishTo!);
+        final targetUri = Uri.parse(publishTo);
         if (!(targetUri.isScheme('http') || targetUri.isScheme('https'))) {
           throw const FormatException('Must be an http or https URL.');
         }
@@ -160,10 +160,10 @@ class Pubspec {
           return _$PubspecFromJson(json);
         } on CheckedFromJsonException catch (e) {
           if (e.map == json && json.containsKey(e.key)) {
-            json = Map.from(json)..remove(e.key);
-            continue;
+            json = {...json}..remove(e.key);
+          } else {
+            rethrow;
           }
-          rethrow;
         }
       }
     }
@@ -183,67 +183,63 @@ class Pubspec {
       );
 
   static List<String> _normalizeAuthors(String? author, List<String>? authors) {
-    final value = <String>{if (author != null) author, ...?authors};
-    return value.toList();
+    if (author == null) return authors ?? const [];
+    return [
+      author,
+      if (authors != null)
+        for (var otherAuthor in authors)
+          if (author != otherAuthor) otherAuthor,
+    ];
   }
 }
 
 Version? _versionFromString(String? input) =>
     input == null ? null : Version.parse(input);
 
-Map<String, VersionConstraint?> _environmentMap(Map? source) =>
-    source?.map((k, value) {
-      final key = k as String;
-      if (key == 'dart') {
-        // github.com/dart-lang/pub/blob/d84173eeb03c3/lib/src/pubspec.dart#L342
-        // 'dart' is not allowed as a key!
-        throw CheckedFromJsonException(
-          source,
-          'dart',
-          'VersionConstraint',
-          'Use "sdk" to for Dart SDK constraints.',
-          badKey: true,
-        );
-      }
-
-      VersionConstraint? constraint;
-      if (value == null) {
-        constraint = null;
-      } else if (value is String) {
-        try {
-          constraint = VersionConstraint.parse(value);
-        } on FormatException catch (e) {
-          throw CheckedFromJsonException(source, key, 'Pubspec', e.message);
-        }
+Map<String, VersionConstraint?> _environmentMap(Map? source) {
+  if (source == null) return {};
+  return source.map((k, value) {
+    final key = k as String;
+    if (key == 'dart') {
+      // github.com/dart-lang/pub/blob/d84173eeb03c3/lib/src/pubspec.dart#L342
+      // 'dart' is not allowed as a key!
+      throw CheckedFromJsonException(
+        source,
+        'dart',
+        'VersionConstraint',
+        'Use "sdk" to for Dart SDK constraints.',
+        badKey: true,
+      );
+    }
 
-        return MapEntry(key, constraint);
-      } else {
-        throw CheckedFromJsonException(
-          source,
-          key,
-          'VersionConstraint',
-          '`$value` is not a String.',
-        );
+    VersionConstraint? constraint;
+    if (value is String) {
+      try {
+        constraint = VersionConstraint.parse(value);
+      } on FormatException catch (e) {
+        throw CheckedFromJsonException(source, key, 'Pubspec', e.message);
       }
+    } else if (value != null) {
+      throw CheckedFromJsonException(
+        source,
+        key,
+        'VersionConstraint',
+        '`$value` is not a String.',
+      );
+    }
+    return MapEntry(key, constraint);
+  });
+}
 
-      return MapEntry(key, constraint);
-    }) ??
-    {};
-
-Map<String, String?> _executablesMap(Map? source) =>
-    source?.map((k, value) {
-      final key = k as String;
-      if (value == null) {
-        return MapEntry(key, null);
-      } else if (value is String) {
-        return MapEntry(key, value);
-      } else {
-        throw CheckedFromJsonException(
-          source,
-          key,
-          'String',
-          '`$value` is not a String.',
-        );
-      }
-    }) ??
-    {};
+Map<String, String?> _executablesMap(Map? source) => {
+  if (source != null)
+    for (final MapEntry(:key as String, :value) in source.entries)
+      key: (value is String?)
+          ? value
+          : (throw CheckedFromJsonException(
+              source,
+              key,
+              'String',
+              '`$value` is not a String.',
+            )),
+};
diff --git a/pkgs/pubspec_parse/lib/src/screenshot.dart b/pkgs/pubspec_parse/lib/src/screenshot.dart
index f5f0be2ea..99a902cb6 100644
--- a/pkgs/pubspec_parse/lib/src/screenshot.dart
+++ b/pkgs/pubspec_parse/lib/src/screenshot.dart
@@ -12,54 +12,28 @@ class Screenshot {
   Screenshot(this.description, this.path);
 }
 
-List<Screenshot> parseScreenshots(List? input) {
-  final res = <Screenshot>[];
-  if (input == null) {
-    return res;
+List<Screenshot> parseScreenshots(List? input) => [
+  if (input != null)
+    for (final e in input)
+      if (e is Map)
+        Screenshot(_readString(e, 'description'), _readString(e, 'path')),
+];
+
+String _readString(Map input, String entryName) {
+  final value = input[entryName];
+  if (value is String) return value;
+  if (value == null) {
+    throw CheckedFromJsonException(
+      input,
+      entryName,
+      'Screenshot',
+      'Missing required key `$entryName`',
+    );
   }
-
-  for (final e in input) {
-    if (e is! Map) continue;
-
-    final description = e['description'];
-    if (description == null) {
-      throw CheckedFromJsonException(
-        e,
-        'description',
-        'Screenshot',
-        'Missing required key `description`',
-      );
-    }
-
-    if (description is! String) {
-      throw CheckedFromJsonException(
-        e,
-        'description',
-        'Screenshot',
-        '`$description` is not a String',
-      );
-    }
-
-    final path = e['path'];
-    if (path == null) {
-      throw CheckedFromJsonException(
-        e,
-        'path',
-        'Screenshot',
-        'Missing required key `path`',
-      );
-    }
-
-    if (path is! String) {
-      throw CheckedFromJsonException(
-        e,
-        'path',
-        'Screenshot',
-        '`$path` is not a String',
-      );
-    }
-
-    res.add(Screenshot(description, path));
-  }
-  return res;
+  throw CheckedFromJsonException(
+    input,
+    entryName,
+    'Screenshot',
+    '`$value` is not a String',
+  );
 }