IFS-based word splitting not implemented

[chaliy]

Description

IFS-based word splitting is largely unimplemented. This affects 36 skipped tests in word-split.test.sh.

Scope

The following features are missing or broken:

• IFS splitting: IFS=:; set -- $var does not split on custom IFS characters
• $@/$* splitting/joining: Unquoted $@ and $* don't split arguments correctly in word context
• Word elision: Empty unquoted variables should be elided (produce no words), but aren't
• Non-whitespace IFS: Non-whitespace IFS characters should produce empty fields between adjacent delimiters
• Mixed whitespace/non-whitespace IFS: Whitespace IFS chars are treated as delimiters with leading/trailing trimming, non-whitespace are not
• set -- with word splitting: set -- $var doesn't produce correct argument count
• Empty IFS: IFS='' should prevent all splitting
• Unset IFS: unset IFS should behave like default $' \t\n'

Repro

# Expected: 3 args (a, b, c)
IFS=:
var="a:b:c"
set -- $var
echo $#    # bashkit outputs: 1 (wrong, should be 3)

# Expected: empty string elided, 2 args
empty=""
set -- 1 $empty 2
echo $#    # bashkit outputs: 3 (wrong, should be 2)

# Expected: "$*" joins with first char of IFS
IFS=:
set -- x 'y z'
echo "$*"  # bashkit outputs: x y z (wrong, should be x:y z)

Test coverage

36 skipped tests in crates/bashkit/tests/spec_cases/bash/word-split.test.sh (PR #351).

Oils reference: https://github.com/oilshell/oil/blob/master/spec/word-split.test.sh

Related

• IFS-based word splitting not implemented #352 (var-op operators depend on word splitting for $@)

[chaliy]

Related issues

• Dollar single-quote $'' syntax not implemented #353 — $'' dollar single-quote syntax
• Nameref (local -n / typeset -n) not implemented #354 — Nameref (local -n / typeset -n)
• Alias expansion not implemented #355 — Alias expansion
• Exit/return codes not truncated to 8-bit range #356 — Exit/return code 8-bit truncation
• Subshell isolation incomplete: functions, cd, traps, positional params leak #357 — Subshell isolation
• Variable operators ${@-val}, ${arr[@]+val} on $@ and arrays broken #358 — Variable operators on $@ and arrays
• Heredoc edge cases: multiple heredocs, pipe ordering, partial quote delimiters #359 — Heredoc edge cases
• Parser does not detect several syntax errors #360 — Parser error detection
• Arithmetic: recursive variable deref, array access, quoted substitution not implemented #361 — Arithmetic dynamic features
• Unicode: ${#x} counts bytes, printf \u/\U escapes missing #362 — Unicode ${#x} and printf \u/\U

All discovered via Oils-inspired test coverage in PR #351.