perf: avoid unnecessary coordinate array copies in hot geometric paths

[bscuron]

Summary

getCoord() defensively copies its result on every call, a global fix for one historical mutating caller (@turf/rhumb-distance, #2167). Adds getCoordRaw(), a non-copying internal variant, and switches every call site that only reads the result (never mutates it or embeds it by reference into a returned GeoJSON object) to use it instead. distance() in particular is a dependency of 23 packages and is often called in tight per-coordinate/per-segment loops.

Also removes a wrap-in-point()-then-getCoord()-unwrap round trip per segment in nearestPointOnLine, using the already-available raw coordinate array directly.

getCoord() (copy-safe) is left in place at the few call sites that embed its result into a returned Feature (centerOfMass, lineSplit, shortestPath), where switching to a raw reference would alias the caller's input geometry.

Performance: this change alone

Benchmarked with each touched package's own bench.ts (Benchmark.js), comparing the parent commit against this one, same machine, same run. Two packages (turf-boolean-point-on-line, turf-directional-mean) produce no usable output from their existing bench.ts in this environment — unrelated pre-existing issue, excluded below. Three packages (turf-ellipse, turf-great-circle, turf-line-split) initially measured as regressions in a single pass; re-measured with the run order reversed and the effect vanished, confirming it was a measurement-order artifact, not a real difference — the corrected (order-verified) numbers are used below.

Package	Before (ops/sec, summed across fixtures)	After	Change
turf-boolean-point-in-polygon	61,638,167	122,800,432	+106%¹
turf-distance-weight	9,964	16,525	+66%
turf-distance	10,317,872	13,262,833	+29%
turf-bearing	16,872,917	20,461,205	+21%
turf-planepoint	31,871,968	38,836,254	+22%
turf-rhumb-bearing	14,273,173	17,286,919	+21%
turf-quadrat-analysis	(low sample count, see below)		+21%²
turf-nearest-point-on-line	1,512,502	1,706,268	+13%
turf-rhumb-distance	11,371,263	12,353,515	+9%
turf-rhumb-destination	8,748,446	9,221,540	+5%
turf-destination	8,802,002	9,041,056	+3%
turf-transform-scale	12,805,425	12,006,329	~0%³
turf-ellipse	674,966	678,980	~0%¹
turf-great-circle	69,250	68,651	~0%¹
turf-line-split	3,186,298	3,193,247	~0%¹

¹ Re-measured with run order reversed to confirm the direction/magnitude is real, not a measurement artifact.
² turf-quadrat-analysis's nearest fixture only gets 5-9 Benchmark.js samples (each iteration takes multiple seconds), so this one has more inherent noise than the others.
³ Within noise; this package's call sites weren't on a hot path materially exercised by its own benchmark fixtures.

turf-boolean-point-in-polygon's point-in-ring test does a getCoord() (now getCoordRaw()) per vertex in a tight ray-casting loop, so it sees the largest, most reproducible win of the set.

Performance: if polyclip-ts's optimization PR also merges

@turf/union, @turf/difference, @turf/intersect, @turf/dissolve, and @turf/mask all depend on polyclip-ts for their core geometry engine. We also have an open performance PR against polyclip-ts itself (luizbarboza/polyclip-ts#26 — BigInt-backed exact arithmetic + memoized segment comparisons, +64% to +90% on its own benchmarks). Benchmarked here by swapping the currently-published polyclip-ts@0.16.8 for a local build of that PR's branch, same fixtures, same machine — this repo's own code (this PR's getCoordRaw change included) held constant on both sides:

Package	Avg. improvement across fixtures
@turf/union	+141%
@turf/difference	+145%
@turf/intersect	+141%
@turf/mask	+165%
@turf/dissolve	+119%

Every fixture in every package improved (no mixed signal here, unlike the table above), and the effect size (roughly 2.2-2.65x) is far larger than any measurement noise observed elsewhere in this testing, including a reversed-order and repeat-run spot check on @turf/mask.

Test plan

• Existing package test suites pass
• Before/after benchmarked per-package via each package's own bench.ts (tables above)
• Suspicious single-pass results re-verified with reversed run order before being trusted

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01VSdmXWDQ2epJKfoGXFKdqT

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https://claude.ai/code/session_01VSdmXWDQ2epJKfoGXFKdqT