Unicode: ${#x} counts bytes, printf \u/\U escapes missing

[chaliy]

Description

Several unicode-related features are missing or incorrect.

Scope

• ${#x} counts bytes not characters: x=café; echo ${#x} outputs 5 instead of 4
• printf '\u03bc' — \u unicode escape not implemented in printf
• printf '\U000003bc' — \U unicode escape not implemented in printf
• $'\u03bc' — covered by Dollar single-quote $'' syntax not implemented #353 ($'' not implemented)

Repro

x=café
echo ${#x}
# bashkit outputs: 5 (byte count)
# expected: 4 (character count)

printf '\u03bc\n'
# bashkit outputs: \u03bc (literal backslash-u)
# expected: μ

Test coverage

6 skipped tests in crates/bashkit/tests/spec_cases/bash/unicode.test.sh (PR #351).

Oils reference: https://github.com/oilshell/oil/blob/master/spec/unicode.test.sh

Related

• Dollar single-quote $'' syntax not implemented #353 ($'' syntax — unicode escapes in dollar-single-quote)