falcon

Rules / Style / prefer-is-not-empty

prefer-is-not-empty

lint/style/prefer-is-not-empty
Same as prefer_is_not_empty · Dart lints

Flags .length comparisons equivalent to a .isNotEmpty check.

Collections and strings expose an isNotEmpty getter that reads as plain intent and, for lazy iterables, can avoid computing the full length. Comparing length against a constant makes the reader infer the meaning, so list.isNotEmpty should replace forms such as length != 0, length > 0, and length >= 1, along with their operand-swapped mirrors (0 != length, 0 < length, 1 <= length). The rule matches any .length property access against the relevant integer literal; it does not verify the receiver actually offers isNotEmpty.

Invalid

example.dartdart
void bad() {
  if (list.length != 0) return;
  if (0 != items.length) return;
  if (str.length > 0) return;
  if (0 < map.length) return;
  if (set.length >= 1) return;
  if (1 <= names.length) return;
}
Use 'isNotEmpty' instead of comparing 'length' to 0.
1void bad() {
2 if (list.length != 0) return;
Use 'isNotEmpty' instead of comparing 'length' to 0.
2 if (list.length != 0) return;
3 if (0 != items.length) return;
Use 'isNotEmpty' instead of comparing 'length' to 0.
3 if (0 != items.length) return;
4 if (str.length > 0) return;
Use 'isNotEmpty' instead of comparing 'length' to 0.
4 if (str.length > 0) return;
5 if (0 < map.length) return;
Use 'isNotEmpty' instead of comparing 'length' to 0.
5 if (0 < map.length) return;
6 if (set.length >= 1) return;
Use 'isNotEmpty' instead of comparing 'length' to 0.
6 if (set.length >= 1) return;
7 if (1 <= names.length) return;

Valid

example.dartdart
void good() {
  if (list.isNotEmpty) return;
  if (items.length == 0) return;
  if (str.length < 1) return;
  if (map.length == 3) return;
  if (set.length > 5) return;
  if (count != 0) return;
}

How to configure

Set the severity of prefer-is-not-empty in your falcon.json:

falcon.jsonjson
{
  "linter": {
    "rules": {
      "style": {
        "prefer-is-not-empty": "error"
      }
    }
  }
}

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