FA-96358 / Phone number formatting / Member archive

Ten-digit display formatter: dotted numbers are rejected · case 03

"302.555.0115" returns None.

Member previewVariant 3 · 3 implementations · 12 checks per implementation

Case contract

Strip the input. Only digits, spaces, parentheses, hyphens, dots and plus are allowed. If the input starts with "+" the digits must start with country digit 1. Eleven digits starting with 1 lose that 1. Exactly ten digits must remain: area (3), exchange (3), line (4). Neither the area nor the exchange may start with 0 or 1 or end in "11". Return "(AAA) EEE-LLLL" or None.

Why this case matters

Ten-digit display formatting is applied to every stored number; accepting impossible numbers or rejecting valid punctuation corrupts contact data.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
dotted input	`null`	`"(504) 555-0137"`	Failed

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