Factor unit inversion in class + in parser

[zoltan-vespertool]

No description provided.

[Copilot]

Pull request overview

This pull request updates unit parsing and inversion behavior so dimensionless factor parts (e.g., SI prefixes like k) correctly participate in exponentiation and denominator inversion, and adds tests around invert() and factor/unit interactions.

Changes:

• Update Parser so FactorUnitPart ratios are raised to the parsed unit power (including negative powers/denominators).
• Add FactorUnitPart::invert() to invert via reciprocal ratio (since factor parts always have power 1).
• Extend test coverage for Unit::invert(), factor inversion, and parsing cases like km^2 and factor units in denominators.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Parser.php	Adjusts how parsed powers are applied to factor parts during expansion of registered units.
src/FactorUnitPart.php	Adds an override for invert() that reciprocates the factor ratio.
tests/UnitTest.php	Adds tests validating Unit::invert() behavior with factor + powered dimension parts.
tests/ParserTest.php	Updates expectations around powered/denominator parsing and adds new parsing tests.
tests/FactorUnitPartTest.php	Adds a unit test for FactorUnitPart::invert().

Comments suppressed due to low confidence (1)

src/Parser.php:49

• When recreating UnitPart instances during parsing, the original offset is dropped (UnitPart::$offset defaults to 0). This breaks parsing of offset units (e.g., celsius/fahrenheit from RegistryBuilder) when they appear in expressions or with powers, because the resulting Unit loses its offset and conversions will be incorrect. Pass through $part->getOffset() when constructing the new UnitPart.

            $parts[] = array_map(function (UnitPart|FactorUnitPart $part) use ($power) {
                if ($part instanceof FactorUnitPart) {
                    return new FactorUnitPart($part->getRatio() ** $power);
                }

                return new UnitPart(
                    $part->getRatio(),
                    $part->getDimension(),
                    $part->getPower() * $power,
                );

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