Library symbol pins are stored Y-up (positive Y is upward in the symbol
editor's coordinate system) but `.kicad_sch` is Y-down (positive Y is
downward in the schematic). `pin_world_xy` was returning `sym_y + ry`
without negating the rotated lib Y, so for any non-symmetric symbol
pin 1 and pin 2 ended up at swapped world positions.
For symmetric two-pin passives (R, C non-polarized) this was invisible
because pin 1 and pin 2 are electrically equivalent. For polarized
parts — electrolytic and polymer caps, diodes, MOSFETs, BJTs — it
silently swapped polarity. A label snapped to a polarized cap's pin 1
ended up on pin 2, which is catastrophic at first power-up.
The order matches eeschema's actual transformation:
mirror in lib space → Y-flip to screen → rotate → translate.
The existing regression test in test_pin_locator_y_flip.py was already
written with the correct expected coordinates but the matching code fix
was never landed; that test now passes.
Three tests in test_move_with_wire_preservation.py had baked the buggy
expected coordinates into their assertions; updated those to the correct
y-flipped values. The touching-pin fixture had to flip R2's Y from
-7.62 to +7.62 so the two pins still meet under the corrected formula.
Verified end-to-end on a 46-component aerospace PDB schematic: all
8 polarized-part pins (4 polymer caps + 4 TVS diodes) now produce
world coordinates that match the labels actually placed in the file.
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