Gleam: two-fer fails locally, passes on site

Programming Gleam
1

My two-fer solution is straightforward:

import gleam/option.{type Option}

pub fn two_fer(name: Option(String)) -> String {
  let id = option.unwrap(name, "you")
  "One for " <> id <> ", one for me."
}

It passes the test-runner.

Testing locally fails with a very cryptic message:

$ gleam test
   Compiled in 0.07s
    Running two_fer_test.main
exception error: #{function => <<"read_module">>,line => 74,
                   message => <<"Assertion pattern match failed">>,
                   module => <<"exercism/test_runner">>,
                   value => {error,not_utf8},
                   gleam_error => let_assert}
  in function  exercism@test_runner:read_module/1 (/home/parallels/src/exercism/exercism.io/gleam/two-fer/build/dev/erlang/exercism_test_runner/_gleam_artefacts/exercism@test_runner.erl, line 96)
  in call from gleam@list:do_map/3 (/home/parallels/src/exercism/exercism.io/gleam/two-fer/build/dev/erlang/gleam_stdlib/_gleam_artefacts/gleam@list.erl, line 119)
  in call from exercism@test_runner:main/0 (/home/parallels/src/exercism/exercism.io/gleam/two-fer/build/dev/erlang/exercism_test_runner/_gleam_artefacts/exercism@test_runner.erl, line 134)

I haven’t seen this with any of the other 20 or so exercises I’ve done.

2

This appears to be an error from simplifile propagating up, but there’s nothing spooky about my source file

$ file src/two_fer.gleam 
src/two_fer.gleam: ASCII text

$ od -c src/two_fer.gleam 
0000000   i   m   p   o   r   t       g   l   e   a   m   /   o   p   t
0000020   i   o   n   .   {   t   y   p   e       O   p   t   i   o   n
0000040   }  \n  \n   p   u   b       f   n       t   w   o   _   f   e
0000060   r   (   n   a   m   e   :       O   p   t   i   o   n   (   S
0000100   t   r   i   n   g   )   )       -   >       S   t   r   i   n
0000120   g       {  \n           l   e   t       i   d       =       o
0000140   p   t   i   o   n   .   u   n   w   r   a   p   (   n   a   m
0000160   e   ,       o   r   :       "   y   o   u   "   )  \n        
0000200   "   O   n   e       f   o   r       "       <   >       i   d
0000220       <   >       "   ,       o   n   e       f   o   r       m
0000240   e   .   "  \n   }  \n
0000246
3

What version of Gleam are you using?

4

Root cause identified: the test runner package is trying to load a hidden vim swap file as a gleam module.

Working it out in exercism/gleam-test-runner#63

4 Likes
5

Great debugging! :slight_smile: