[CoreLib] String.splitMap

Introduced a new public method splitMap to convert image into a generic iterable,
inspired by splitMapJoin, this new method uses the same parameters and returns Iterable<T>

Closes dart-lang#40072

pkg/dev_compiler/test/nullable_inference_test.dart

@@ -243,6 +243,7 @@ void main() {
         s.replaceRange(1, 2, s);
         s.split(s);
         s.splitMapJoin(s, onMatch: (_) => s, onNonMatch: (_) => s);
+        s.splitMap(s, onMatch: (_) => s, onNonMatch: (_) => s);
         s.startsWith(s);
         s.substring(1);
         s.toLowerCase();

pkg/linter/lib/src/rules/null_closures.dart

@@ -91,6 +91,10 @@ final Map<String, Set<NonNullableFunction>>
     NonNullableFunction('dart.core', 'String', 'splitMapJoin',
         named: ['onMatch', 'onNonMatch']),
   },
+  'splitMap': {
+    NonNullableFunction('dart.core', 'Iterable', 'splitMap',
+      named: ['onMatch', 'onNonMatch']),
+  },
   'takeWhile': {
     NonNullableFunction('dart.core', 'Iterable', 'takeWhile', positional: [0]),
   },

pkg/linter/messages.yaml

@@ -7037,6 +7037,7 @@ LintCode:
         * `String.replaceAllMapped` at the 1st positional parameter
         * `String.replaceFirstMapped` at the 1st positional parameter
         * `String.splitMapJoin` at the named parameters `onMatch` and `onNonMatch`
+        * `String.splitMap` at the named parameter `onMatch` and `onNonMatch`
 
       **BAD:**
       ```dart

pkg/linter/tool/machine/rules.json

@@ -1532,7 +1532,7 @@
     "incompatible": [],
     "sets": [],
     "fixStatus": "hasFix",
-    "details": "**DON'T** pass `null` as an argument where a closure is expected.\n\nOften a closure that is passed to a method will only be called conditionally,\nso that tests and \"happy path\" production calls do not reveal that `null` will\nresult in an exception being thrown.\n\nThis rule only catches null literals being passed where closures are expected\nin the following locations:\n\n#### Constructors\n\n* From `dart:async`\n  * `Future` at the 0th positional parameter\n  * `Future.microtask` at the 0th positional parameter\n  * `Future.sync` at the 0th positional parameter\n  * `Timer` at the 0th positional parameter\n  * `Timer.periodic` at the 1st positional parameter\n* From `dart:core`\n  * `List.generate` at the 1st positional parameter\n\n#### Static functions\n\n* From `dart:async`\n  * `scheduleMicrotask` at the 0th positional parameter\n  * `Future.doWhile` at the 0th positional parameter\n  * `Future.forEach` at the 0th positional parameter\n  * `Future.wait` at the named parameter `cleanup`\n  * `Timer.run` at the 0th positional parameter\n\n#### Instance methods\n\n* From `dart:async`\n  * `Future.then` at the 0th positional parameter\n  * `Future.complete` at the 0th positional parameter\n* From `dart:collection`\n  * `Queue.removeWhere` at the 0th positional parameter\n  * `Queue.retain\n  * `Iterable.firstWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.forEach` at the 0th positional parameter\n  * `Iterable.fold` at the 1st positional parameter\n  * `Iterable.lastWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.map` at the 0th positional parameter\n  * `Iterable.reduce` at the 0th positional parameter\n  * `Iterable.singleWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.skipWhile` at the 0th positional parameter\n  * `Iterable.takeWhile` at the 0th positional parameter\n  * `Iterable.where` at the 0th positional parameter\n  * `List.removeWhere` at the 0th positional parameter\n  * `List.retainWhere` at the 0th positional parameter\n  * `String.replaceAllMapped` at the 1st positional parameter\n  * `String.replaceFirstMapped` at the 1st positional parameter\n  * `String.splitMapJoin` at the named parameters `onMatch` and `onNonMatch`\n\n**BAD:**\n```dart\n[1, 3, 5].firstWhere((e) => e.isOdd, orElse: null);\n```\n\n**GOOD:**\n```dart\n[1, 3, 5].firstWhere((e) => e.isOdd, orElse: () => null);\n```",
+    "details": "**DON'T** pass `null` as an argument where a closure is expected.\n\nOften a closure that is passed to a method will only be called conditionally,\nso that tests and \"happy path\" production calls do not reveal that `null` will\nresult in an exception being thrown.\n\nThis rule only catches null literals being passed where closures are expected\nin the following locations:\n\n#### Constructors\n\n* From `dart:async`\n  * `Future` at the 0th positional parameter\n  * `Future.microtask` at the 0th positional parameter\n  * `Future.sync` at the 0th positional parameter\n  * `Timer` at the 0th positional parameter\n  * `Timer.periodic` at the 1st positional parameter\n* From `dart:core`\n  * `List.generate` at the 1st positional parameter\n\n#### Static functions\n\n* From `dart:async`\n  * `scheduleMicrotask` at the 0th positional parameter\n  * `Future.doWhile` at the 0th positional parameter\n  * `Future.forEach` at the 0th positional parameter\n  * `Future.wait` at the named parameter `cleanup`\n  * `Timer.run` at the 0th positional parameter\n\n#### Instance methods\n\n* From `dart:async`\n  * `Future.then` at the 0th positional parameter\n  * `Future.complete` at the 0th positional parameter\n* From `dart:collection`\n  * `Queue.removeWhere` at the 0th positional parameter\n  * `Queue.retain\n  * `Iterable.firstWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.forEach` at the 0th positional parameter\n  * `Iterable.fold` at the 1st positional parameter\n  * `Iterable.lastWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.map` at the 0th positional parameter\n  * `Iterable.reduce` at the 0th positional parameter\n  * `Iterable.singleWhere` at the 0th positional parameter, and the named\n    parameter `orElse`\n  * `Iterable.skipWhile` at the 0th positional parameter\n  * `Iterable.takeWhile` at the 0th positional parameter\n  * `Iterable.where` at the 0th positional parameter\n  * `List.removeWhere` at the 0th positional parameter\n  * `List.retainWhere` at the 0th positional parameter\n  * `String.replaceAllMapped` at the 1st positional parameter\n  * `String.replaceFirstMapped` at the 1st positional parameter\n  * `String.splitMapJoin` at the named parameters `onMatch` and `onNonMatch`  * `String.splitMap` at the named parameters `onMatch` and `onNonMatch`\n\n**BAD:**\n```dart\n[1, 3, 5].firstWhere((e) => e.isOdd, orElse: null);\n```\n\n**GOOD:**\n```dart\n[1, 3, 5].firstWhere((e) => e.isOdd, orElse: () => null);\n```",
     "sinceDartSdk": "2.0"
   },
   {

sdk/lib/_internal/js_dev_runtime/private/js_string.dart

@@ -83,6 +83,103 @@ final class JSString extends Interceptor
     return stringReplaceAllFuncUnchecked(this, from, onMatch, onNonMatch);
   }
 
+  @notNull
+  Iterable<T> splitMap<T>(
+      Pattern pattern, {
+      T Function(Match match)? onMatch,
+      T Function(String nonMatch)? onNonMatch,
+    }) {
+      return stringSplitMapUnchecked(this, pattern, onMatch, onNonMatch);
+    }
+
+    Iterable<T> stringSplitMapUnchecked<T>(String receiver, Pattern pattern,
+      T Function(Match)? onMatch, T Function(String)? onNonMatch) {
+    onMatch ??= (match) => match[0]! as T;
+    onNonMatch ??= (string) => string as T;
+    if (pattern is String) {
+      return stringSplitStringMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+    }
+    if (pattern is JSSyntaxRegExp) {
+      return stringSplitJSRegExpMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+    }
+    return stringSplitGeneralMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+  }
+
+  Iterable<T> stringSplitStringMapUnchecked<T>(String receiver, String pattern,
+      T Function(Match) onMatch, T Function(String) onNonMatch) {
+    if (pattern.isEmpty) {
+      return stringSplitEmptyMapUnchecked(receiver, onMatch, onNonMatch);
+    }
+    List<T> result = <T>[];
+    int startIndex = 0;
+    int patternLength = pattern.length;
+    while (true) {
+      int position = stringIndexOfStringUnchecked(receiver, pattern, startIndex);
+      if (position == -1) {
+        break;
+      }
+      result.add(onNonMatch(receiver.substring(startIndex, position)));
+      result.add(onMatch(StringMatch(position, receiver, pattern)));
+      startIndex = position + patternLength;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
+  Iterable<T> stringSplitEmptyMapUnchecked<T>(
+      String receiver, T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int length = receiver.length;
+    int i = 0;
+    result.add(onNonMatch(""));
+    while (i < length) {
+      result.add(onMatch(StringMatch(i, receiver, "")));
+      // Special case to avoid splitting a surrogate pair.
+      int code = receiver.codeUnitAt(i);
+      if ((code & ~0x3FF) == 0xD800 && length > i + 1) {
+        // Leading surrogate;
+        code = receiver.codeUnitAt(i + 1);
+        if ((code & ~0x3FF) == 0xDC00) {
+          // Matching trailing surrogate.
+          result.add(onNonMatch(receiver.substring(i, i + 2)));
+          i += 2;
+          continue;
+        }
+      }
+      result.add(onNonMatch(receiver[i]));
+      i++;
+    }
+    result.add(onMatch(StringMatch(i, receiver, "")));
+    result.add(onNonMatch(""));
+    return result;
+  }
+
+  Iterable<T> stringSplitJSRegExpMapUnchecked<T>(String receiver,
+      JSSyntaxRegExp pattern, T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int startIndex = 0;
+    for (Match match in pattern.allMatches(receiver)) {
+      result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+      result.add(onMatch(match));
+      startIndex = match.end;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
+  Iterable<T> stringSplitGeneralMapUnchecked<T>(String receiver, Pattern pattern,
+      T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int startIndex = 0;
+    for (Match match in pattern.allMatches(receiver)) {
+      result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+      result.add(onMatch(match));
+      startIndex = match.end;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
   @notNull
   String replaceFirst(
     Pattern from,

sdk/lib/_internal/js_runtime/lib/interceptors.dart

@@ -42,6 +42,7 @@ import 'dart:_js_helper'
         stringIndexOfStringUnchecked,
         stringLastIndexOfUnchecked,
         stringReplaceAllFuncUnchecked,
+        stringSplitMapUnchecked,
         stringReplaceAllUnchecked,
         stringReplaceFirstUnchecked,
         stringReplaceFirstMappedUnchecked,

sdk/lib/_internal/js_runtime/lib/js_string.dart

@@ -72,13 +72,106 @@ final class JSString extends Interceptor
     return stringReplaceAllFuncUnchecked(this, from, onMatch, onNonMatch);
   }
 
+  Iterable<T> splitMap<T>(Pattern pattern, 
+      {T Function(Match match)? onMatch, T Function(String nonMatch)? onNonMatch}) {
+    return stringSplitMapUnchecked(this, pattern, onMatch, onNonMatch); 
+  }
+
   String replaceFirst(Pattern from, String to, [int startIndex = 0]) {
     checkString(to);
     checkInt(startIndex);
     RangeError.checkValueInInterval(startIndex, 0, this.length, "startIndex");
     return stringReplaceFirstUnchecked(this, from, to, startIndex);
   }
 
+  Iterable<T> stringSplitMapUnchecked<T>(String receiver, Pattern pattern,
+    T Function(Match)? onMatch, T Function(String)? onNonMatch) {
+    onMatch ??= (match) => match[0]! as T;
+    onNonMatch ??= (string) => string as T;
+    if (pattern is String) {
+      return stringSplitStringMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+    }
+    if (pattern is JSSyntaxRegExp) {
+      return stringSplitJSRegExpMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+    }
+    return stringSplitGeneralMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+  }
+
+  Iterable<T> stringSplitStringMapUnchecked<T>(String receiver, String pattern,
+      T Function(Match) onMatch, T Function(String) onNonMatch) {
+    if (pattern.isEmpty) {
+      return stringSplitEmptyMapUnchecked(receiver, onMatch, onNonMatch);
+    }
+    List<T> result = <T>[];
+    int startIndex = 0;
+    int patternLength = pattern.length;
+    while (true) {
+      int position = stringIndexOfStringUnchecked(receiver, pattern, startIndex);
+      if (position == -1) {
+        break;
+      }
+      result.add(onNonMatch(receiver.substring(startIndex, position)));
+      result.add(onMatch(StringMatch(position, receiver, pattern)));
+      startIndex = position + patternLength;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
+  Iterable<T> stringSplitEmptyMapUnchecked<T>(
+      String receiver, T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int length = receiver.length;
+    int i = 0;
+    result.add(onNonMatch(""));
+    while (i < length) {
+      result.add(onMatch(StringMatch(i, receiver, "")));
+      // Special case to avoid splitting a surrogate pair.
+      int code = receiver.codeUnitAt(i);
+      if ((code & ~0x3FF) == 0xD800 && length > i + 1) {
+        // Leading surrogate;
+        code = receiver.codeUnitAt(i + 1);
+        if ((code & ~0x3FF) == 0xDC00) {
+          // Matching trailing surrogate.
+          result.add(onNonMatch(receiver.substring(i, i + 2)));
+          i += 2;
+          continue;
+        }
+      }
+      result.add(onNonMatch(receiver[i]));
+      i++;
+    }
+    result.add(onMatch(StringMatch(i, receiver, "")));
+    result.add(onNonMatch(""));
+    return result;
+  }
+
+  Iterable<T> stringSplitJSRegExpMapUnchecked<T>(String receiver,
+      JSSyntaxRegExp pattern, T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int startIndex = 0;
+    for (Match match in pattern.allMatches(receiver)) {
+      result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+      result.add(onMatch(match));
+      startIndex = match.end;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
+  Iterable<T> stringSplitGeneralMapUnchecked<T>(String receiver, Pattern pattern,
+      T Function(Match) onMatch, T Function(String) onNonMatch) {
+    List<T> result = <T>[];
+    int startIndex = 0;
+    for (Match match in pattern.allMatches(receiver)) {
+      result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+      result.add(onMatch(match));
+      startIndex = match.end;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex)));
+    return result;
+  }
+
   String replaceFirstMapped(Pattern from, String replace(Match match),
       [int startIndex = 0]) {
     checkNull(replace);

sdk/lib/_internal/js_runtime/lib/string_helper.dart

@@ -264,6 +264,94 @@ String stringReplaceAllFuncUnchecked(String receiver, Pattern pattern,
   return buffer.toString();
 }
 
+Iterable<T> stringSplitMapUnchecked<T>(String receiver, Pattern pattern,
+    T Function(Match)? onMatch, T Function(String)? onNonMatch) {
+  onMatch ??= (match) => match[0]! as T;
+  onNonMatch ??= (string) => string as T;
+  if (pattern is String) {
+    return stringSplitStringMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+  }
+  if (pattern is JSSyntaxRegExp) {
+    return stringSplitJSRegExpMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+  }
+  return stringSplitGeneralMapUnchecked(receiver, pattern, onMatch, onNonMatch);
+}
+
+Iterable<T> stringSplitStringMapUnchecked<T>(String receiver, String pattern,
+    T Function(Match) onMatch, T Function(String) onNonMatch) {
+  if (pattern.isEmpty) {
+    return stringSplitEmptyMapUnchecked(receiver, onMatch, onNonMatch);
+  }
+  List<T> result = <T>[];
+  int startIndex = 0;
+  int patternLength = pattern.length;
+  while (true) {
+    int position = stringIndexOfStringUnchecked(receiver, pattern, startIndex);
+    if (position == -1) {
+      break;
+    }
+    result.add(onNonMatch(receiver.substring(startIndex, position)));
+    result.add(onMatch(StringMatch(position, receiver, pattern)));
+    startIndex = position + patternLength;
+  }
+  result.add(onNonMatch(receiver.substring(startIndex)));
+  return result;
+}
+
+Iterable<T> stringSplitEmptyMapUnchecked<T>(
+    String receiver, T Function(Match) onMatch, T Function(String) onNonMatch) {
+  List<T> result = <T>[];
+  int length = receiver.length;
+  int i = 0;
+  result.add(onNonMatch(""));
+  while (i < length) {
+    result.add(onMatch(StringMatch(i, receiver, "")));
+    // Special case to avoid splitting a surrogate pair.
+    int code = receiver.codeUnitAt(i);
+    if ((code & ~0x3FF) == 0xD800 && length > i + 1) {
+      // Leading surrogate;
+      code = receiver.codeUnitAt(i + 1);
+      if ((code & ~0x3FF) == 0xDC00) {
+        // Matching trailing surrogate.
+        result.add(onNonMatch(receiver.substring(i, i + 2)));
+        i += 2;
+        continue;
+      }
+    }
+    result.add(onNonMatch(receiver[i]));
+    i++;
+  }
+  result.add(onMatch(StringMatch(i, receiver, "")));
+  result.add(onNonMatch(""));
+  return result;
+}
+
+Iterable<T> stringSplitJSRegExpMapUnchecked<T>(String receiver,
+    JSSyntaxRegExp pattern, T Function(Match) onMatch, T Function(String) onNonMatch) {
+  List<T> result = <T>[];
+  int startIndex = 0;
+  for (Match match in pattern.allMatches(receiver)) {
+    result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+    result.add(onMatch(match));
+    startIndex = match.end;
+  }
+  result.add(onNonMatch(receiver.substring(startIndex)));
+  return result;
+}
+
+Iterable<T> stringSplitGeneralMapUnchecked<T>(String receiver, Pattern pattern,
+    T Function(Match) onMatch, T Function(String) onNonMatch) {
+  List<T> result = <T>[];
+  int startIndex = 0;
+  for (Match match in pattern.allMatches(receiver)) {
+    result.add(onNonMatch(receiver.substring(startIndex, match.start)));
+    result.add(onMatch(match));
+    startIndex = match.end;
+  }
+  result.add(onNonMatch(receiver.substring(startIndex)));
+  return result;
+}
+
 String stringReplaceAllEmptyFuncUnchecked(String receiver,
     String Function(Match) onMatch, String Function(String) onNonMatch) {
   // Pattern is the empty string.