Fish 4.0: The Fish of Theseus

Overall reception

• Many commenters are enthusiastic long‑time fish users; several report switching from bash/zsh and never looking back.
• Common theme: “just works out of the box” with minimal config, compared to zsh+plugin stacks.
• Some are impressed the full Rust port was completed in ~2 years and consider that fast for 50k+ LOC.

Fish vs. bash/zsh and other shells

• Pros of fish:
  • Strong interactive UX: autosuggestions, syntax highlighting, rich completions, history search, multiline editing, good built‑ins (string, math, argparse), Docker/Git‑aware completions.
  • Beginner‑friendly and low‑config; web-based config and simple function/prompt model.
  • Some see advantages from being a clean non‑POSIX design (avoids legacy shell oddities and vulnerabilities).
• Cons / reasons to stay with bash/zsh:
  • Non‑POSIX syntax: can’t directly source .bashrc, bash snippets sometimes break; here‑docs/<<< missing; set -e semantics absent.
  • Fish scripting seen as mainly for extending fish; for “serious” scripts many prefer bash or another language.
  • Several use fish interactively but keep scripts in bash via shebangs.
  • Some prefer zsh’s flexibility and larger completion/plugin ecosystem.

Rust rewrite, portability, and tooling

• Rust seen as improving maintainability, safety, and cross‑compilation experience (especially with custom feature‑detection crate).
• Port did not ship a C++/Rust hybrid; transitional bindings were kept off releases to avoid distro pain.
• Loss of Cygwin support due to missing Rust target is widely noted; some find it “sad” given reliance on Cygwin in corporate Windows environments.
• Debate over portability:
  • One side: C++ (via GCC) clearly supports more obscure platforms.
  • Other side: Rust offers better tooling (rustup, cross‑platform crates) and higher ROI for mainstream targets.

Build, packaging, and Cargo limitations

• Fish still uses CMake for installation because Cargo’s install model is binary‑centric and weak on data/docs layout.
• Discussion around whether Cargo should grow richer install hooks vs. delegating that to higher‑level tools.
• Distro packagers report it’s workable when upstream cooperates; fish maintainers say they design with packager requirements in mind.

Language behavior & configuration probing

• Discussion of feature detection vs version detection; several argue feature detection is better but traditional autoconf‑style probing is fragile.
• Rust’s cfg! vs #[cfg] trade‑offs are discussed in terms of catching misconfigurations across build variants.

Miscellaneous

• Some worry about LOC increase (56k C++ → 75k Rust); maintainers attribute most of this to rustfmt’s more vertical style, not more “significant” code.