src/run/bend.bend

ezx@1.6.0.0 · 28 lines · 0 definitions

1# run/bend: which bend is on the PATH, asked the way that bend will answer.
2#
3# bend has had the question two ways round. Up to 2.0.16 it is `bend --version`
4# and `bend version` is "no such file: version"; from 2.0.18 on it is `bend
5# version` and the flag is "unknown option --version". Either way the spelling
6# it does not know exits non-zero, which looks exactly like a bend that is not
7# installed — so a caller that asks only one way cannot tell a missing bend
8# from an old one, and ez has two callers that need the banner: doctor's
9# report and the toolchain part of a cache key.
10# Asking both ways, current spelling first, is the whole of this module.
11import Base
12import snap@1.3.0.0/main.bend as R
13
14# the older spelling, tried only when the current one was not understood
15def version.older(ok: Bool, out: String) -> IO(String):
16  match ok:
17    case True{}:
18      IO.pure(String, out)
19    case False{}:
20      R.exec(["bend", "--version"])
21
22# `bend` asked which bend it is, as a run's answer: the status line, then the
23# banner. A bend that is not on the PATH fails both spellings, so the status
24# an absent bend answers with is still the one the caller sees.
25def version() -> IO(String):
26  do IO<String>:
27    +out : String <- R.exec(["bend", "version"])
28    version.older(R.ok(out), out)