fix: length rules reject a valid length of 0

[shakurShirajul]

Summary

The min, max, and between rules rejected any value whose length is 0. An empty string, an empty array, and the numbers 0 / 0.0 all failed validation even when the configured bounds explicitly allowed a length of zero — min:0, max:5, and between:0,5 would each reject ''.

The cause is a truthiness check on a length value:

$length = $this->getValueLength($value);

if ($length) {          // 0 is falsy, so a valid length of 0 falls through
    return $length >= $min;
}

return false;           // ...and is reported as a failure

getValueLength() returns an integer length, or false when the value has no measurable length at all (bool, null, object). Because 0 and false are both falsy, the guard could not tell "this value is legitimately empty" from "this value cannot be measured", and collapsed both into a failure.

This PR distinguishes the two, and moves the distinction into the shared helper so it is made in exactly one place.

Behaviour change

Only values with a length of 0 are affected. Verified before/after:

Value	min:0	max:5	between:0,5
''	false → true	false → true	false → true
[]	false → true	false → true	false → true
0	false → true	false → true	false → true
0.0	false → true	false → true	false → true

Everything else is untouched. Non-zero bounds behave identically to before (min:3 still accepts 'abc' and rejects 'ab'), and values with no measurable length — true, null, new stdClass() — still fail, as they should.

Note this only changes whether an empty value passes a length rule. It does not make empty values pass validation overall: required is still the rule that rejects them, which is the correct separation of concerns. A field declared min:0 was always meant to accept an empty value.

Changes

Fix — added Helpers::lengthWithin() next to getValueLength() in the trait all three rules already use. It decodes the false sentinel once and applies the bounds, with null meaning "no bound on this side":

protected function lengthWithin($value, $min = null, $max = null): bool

MinRule, MaxRule, and BetweenRule now each delegate to it in a single line rather than repeating the same guard three times. The original fix applied the corrected check separately in all three classes; consolidating it means a future length-based rule cannot reintroduce the bug by writing if ($length) again, and there is one definition of what a measurable length is.

Tests — added coverage to MinTest, MaxTest, and BetweenTest for the three distinct cases the old code conflated:

• normal boundary behaviour (lengths above/below/at the bound)
• a length of 0 is accepted, for strings, arrays, and numbers
• values with no measurable length (true, null, stdClass) are still rejected

The previously commented-out array assertion in MaxTest is now enabled.

Developer tooling — added composer test:watch (bin/test-watch), which re-runs the suite when a PHP file under src/ or tests/ changes. It delegates to the existing test:unit script so there is a single definition of the test command, and uses plain polling so it needs no extra dependencies. Added /bin export-ignore to .gitattributes so this dev-only script is not shipped in the distributed package, and documented the two commands briefly under Contributing.

Testing

composer test:unit — 36 tests, 123 assertions, all passing.

Before/after behaviour in the table above was verified by running both revisions of the rules directly against each value.

Compatibility

No API changes. lengthWithin() is a new protected trait method; getValueLength() keeps its existing signature and return contract, so any code extending Rule or using Helpers continues to work unchanged. PHP 7.2+ compatible, consistent with the package's existing constraint.

One caveat worth calling out for reviewers: if a project currently relies on min:0 or between:0,N to reject empty values, that behaviour was a bug and this PR ends it. Such a field should use required instead.

[Copilot]

Pull request overview

Fixes an edge case in WPValidator’s length-based rules where a valid computed length of 0 was treated as falsy and incorrectly rejected. The change ensures only “unmeasurable” values (where getValueLength() returns false) short-circuit validation, while a real length/value of 0 proceeds through comparisons.

Changes:

• Update BetweenRule, MinRule, and MaxRule to guard on $length === false rather than truthiness.
• Expand rule test coverage to include zero-length/value cases (0, 0.0, '', []) and explicitly unmeasurable cases (true, null, stdClass).
• Add boundary-negative assertions in existing min/max/between tests to validate rejection beyond configured limits.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Rules/MinRule.php	Treat 0 as a valid measurable length/value; only false (unmeasurable) fails fast.
src/Rules/MaxRule.php	Same fix as MinRule for max comparisons (accepts 0).
src/Rules/BetweenRule.php	Same fix as Min/Max for range comparisons (accepts 0).
tests/Rules/MinTest.php	Adds coverage for zero-length acceptance, unmeasurable rejection, and boundary negatives.
tests/Rules/MaxTest.php	Adds coverage for zero-length acceptance, unmeasurable rejection, and boundary negatives.
tests/Rules/BetweenTest.php	Adds coverage for zero-length acceptance, unmeasurable rejection, and boundary negatives.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 11 changed files in this pull request and generated no new comments.

[Copilot]

🟡 Changes recommended

Reject non-numeric floats such as NAN and resolve the documented watcher-tooling and guidance inconsistencies.

Get a fresh assessment by requesting another Copilot review.

Review details

Suppressed comments (1)

src/Helpers.php:40

• Because getValueLength() accepts every float, this also receives NAN. For a min-only call, NAN < $min is false and the open-ended max causes the final expression to return true, whereas the previous implementation rejected it (NAN >= $min is false). Reject non-numeric float values such as NAN before applying the bounds so this fix only changes legitimate zero lengths.

        if ($length === false) {
            return false;

• Files reviewed: 8/9 changed files
• Comments generated: 2
• Review effort level: Lite

[Copilot]

🔵 Needs a closer look

Unresolved issues include a NAN regression, inaccurate SizeRule guidance, and missing advertised test-watch tooling.

Review details

Suppressed comments (3)

CLAUDE.md:69

• This guidance says size should use lengthWithin, but SizeRule::validate() still implements its own string/int/array comparisons and never calls this helper. That makes the documented invariant false and can mislead future rule changes; either migrate SizeRule with compatibility tests or remove size from this sentence.

`lengthWithin($value, $min, $max)` wraps both and is what `between`, `min`, `max`, and `size` should use (`null` for an open bound) rather than comparing lengths by hand.

CLAUDE.md:14

• The PR description says this change adds composer test:watch, bin/test-watch, and documentation for it, but this checkout has no bin/test-watch and composer.json still defines only test:unit, compat, and rector. The advertised developer tooling is therefore not delivered; please add the missing files/script/docs or remove that scope from the description.

composer test:unit                                  # full suite (Pest, --testdox, excludes group 'db')

src/Helpers.php:47

• Because the lower-bound check only rejects $length < $min, a NAN float (which getValueLength() accepts as a float) skips that check; with $max === null, the final expression then returns true. The previous MinRule comparison ($length >= $min) rejected NAN, so this is a regression. Use the positive lower-bound comparison or explicitly reject non-finite lengths.

        if ($min !== null && $length < $min) {
            return false;
        }

        return $max === null || $length <= $max;

• Files reviewed: 8/9 changed files
• Comments generated: 0 new
• Review effort level: Lite