Common-Test may try to create directory names that are longer than system limit

[jcpetruzza]

Describe the bug When running a test specification that selects only certain tests to run, CT will create a separate directory per test, and the name of the directory seems to be a concatenation of:

• The two last directories of the suite path
• The suite name
• The word "groups"
• The name of the testcase
• The word "logs"

The problem is that, e.g., on Linux there is a 255 byte limit for filenames and it is not hard to end up going over that limit (e.g. suite-name and testcase name of 60 chars each is not unheard of), in which case CT fails. Instead, CT should truncate and/or use a hash.

buck2's test-runner uses this internally to run CT tests, so it is particularly affected

To Reproduce

$ cat fails.spec
{groups,"/tmp/some_directory_with_a_quite_very_long_name/another_directory_that_just_happened_to_also_have_an_unusually_long_name",
    it_is_not_surprising_that_now_we_also_get_another_long_name_in_the_SUITE,
    [[my_group]],
    {cases,[test_with_a_name_that_is_descriptive_which_is_nice_but_alas_now_too_long]}
}.
{ct_hooks,[]}.
{auto_compile,true}.
{logdir,"/tmp/some_directory_with_a_quite_very_long_name/another_directory_that_just_happened_to_also_have_an_unusually_long_name/logs"}.

$ cat it_is_not_surprising_that_now_we_also_get_another_long_name_in_the_SUITE.erl
module(it_is_not_surprising_that_now_we_also_get_another_long_name_in_the_SUITE).

-export([
    all/0,
    groups/0,
    test_with_a_name_that_is_descriptive_which_is_nice_but_alas_now_too_long/1
]).

all() ->
  [ {group, my_group} ].

groups() ->
    [
        {my_group, [], [ test_with_a_name_that_is_descriptive_which_is_nice_but_alas_now_too_long ]}
    ].

test_with_a_name_that_is_descriptive_which_is_nice_but_alas_now_too_long(_Config) ->
    ok.

$ ct_run -spec fails.spec
Erlang/OTP 25 [erts-13.1.5] [source-5a804b540d] [64-bit] [smp:36:36] [ds:36:36:10] [async-threads:1] [jit:ns] [systemtap]



Common Test v1.23.3 starting (cwd is /tmp/some_directory_with_a_quite_very_long_name/another_directory_that_just_happened_to_also_have_an_unusually_long_name)

Eshell V13.1.5  (abort with ^G)
(ct@80108)1> 
Common Test: Running make in test directories...

CWD set to: "/tmp/some_directory_with_a_quite_very_long_name/another_directory_that_just_happened_to_also_have_an_unusually_long_name/logs/[email protected]_10.39.43"

TEST INFO: 1 test(s), 1 case(s) in 1 suite(s)

EXIT, reason {cannot_create_log_dir,{{error,enametoolong},
"/tmp/some_directory_with_a_quite_very_long_name/another_directory_that_just_happened_to_also_have_an_unusually_long_name/logs/[email protected]_10.39.43/some_directory_with_a_quite_very_long_name.another_directory_that_just_happened_to_also_have_an_unusually_long_name.it_is_not_surprising_that_now_we_also_get_another_long_name_in_the_SUITE.groups.test_with_a_name_that_is_descriptive_which_is_nice_but_alas_now_too_long.logs"}}}}},
...

Expected behavior CT runs the specified tests without problems, just like when running the whole suite

Affected versions Tried it on OTP 25, I suppose older versions are affected as well

[u3s]

thanks for the report. we need to schedule fixing that for a bit later due to priorities :-(