Ale: kotlinc doesn't show errors from stderr

[LovecraftianHorror]

Information

VIM version

NVIM v0.4.3
Build type: Release

Operating System: Arch Linux, Linux Kernel 5.5.4

What went wrong

I was trying to use kotlinc to lint kotlin files and noticed it wasn't showing any lints, even from the following file hello.kt

fun main(args: Array<String>) {
    bad
}

Running essentially the same command listed in :ALEInfo /bin/zsh -c 'kotlinc "/home/lovecraft/hello.kt"' returns

/home/lovecraft/hello.kt:2:2: error: unresolved reference: bad
    bad
 ^

I think the problem stems from kotlinc outputting to stderr instead of stdout. My hacky way of testing this was to move kotlinc to kotlinc.orig and create a new kotlinc that redirects stderr to stdout like below

#!/usr/bin/bash

kotlinc.orig "$@" 2>&1

After that ALE correctly displays the error in hello.kt. Hopefully any of this is helpful, I really appreciate all the work the ALE maintainers have put into such a great plugin!

Reproducing the bug

1. Install kotlinc
2. Create a file with the same contents as hello.kt
3. Run ALE and see there are no errors shown

:ALEInfo

 Current Filetype: kotlin
Available Linters: ['kotlinc', 'ktlint', 'languageserver']
  Enabled Linters: ['kotlinc', 'ktlint', 'languageserver']
 Suggested Fixers: 
  'remove_trailing_lines' - Remove all blank lines at the end of a file.
  'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
 Linter Variables:

let g:ale_kotlin_kotlinc_classpath = ''
let g:ale_kotlin_kotlinc_config_file = '.ale_kotlinc_config'
let g:ale_kotlin_kotlinc_enable_config = 0
let g:ale_kotlin_kotlinc_module_filename = 'module.xml'
let g:ale_kotlin_kotlinc_options = ''
let g:ale_kotlin_kotlinc_sourcepath = ''
let g:ale_kotlin_kotlinc_use_module_file = 0
let g:ale_kotlin_languageserver_executable = 'kotlin-language-server'
 Global Variables:

let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = 0
let g:ale_command_wrapper = ''
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = 0
let g:ale_completion_max_suggestions = v:null
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'E'
let g:ale_echo_msg_format = '[%linter%] [%severity%] %code:%%s'
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'W'
let g:ale_enabled = 1
let g:ale_fix_on_save = 0
let g:ale_fixers = {'c': ['clang-format'], 'rust': ['rustfmt'], 'cpp': ['clang-format'], 'python': ['black']}
let g:ale_history_enabled = 1
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 1000
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_insert_leave = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {}
let g:ale_linters_explicit = 0
let g:ale_list_vertical = 0
let g:ale_list_window_size = 10
let g:ale_loclist_msg_format = '[%linter%] [%severity%] %code:%%s'
let g:ale_lsp_root = {}
let g:ale_max_buffer_history_size = 20
let g:ale_max_signs = -1
let g:ale_maximum_file_size = v:null
let g:ale_open_list = 0
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_set_balloons = 0
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = 1
let g:ale_sign_error = 'XX'
let g:ale_sign_info = '!!'
let g:ale_sign_offset = 1000000
let g:ale_sign_style_error = 'XX'
let g:ale_sign_style_warning = '!!'
let g:ale_sign_warning = '!!'
let g:ale_sign_highlight_linenrs = 0
let g:ale_statusline_format = v:null
let g:ale_type_map = {}
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 0
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1
  Command History:

(executable check - success) kotlinc
(finished - exit code 1) ['/bin/zsh', '-c', 'kotlinc    ''/home/lovecraft/hello.kt''']

<<<NO OUTPUT RETURNED>>>

(executable check - failure) ktlint

[ndtho8205]

I am also dealing with the same problem. Big thanks for your suggestion, it seems like the code forgot to set output_stream when running the kotlinc linter (kotlinc.vim#L176).

'output_stream': 'stderr'

So I added one line only and it works.

call ale#linter#Define('kotlin', {
\   'name': 'kotlinc',
\   'executable': 'kotlinc',
\   'output_stream': 'stderr',           <------ add this line
\   'command': function('ale_linters#kotlin#kotlinc#RunWithImportPaths'),
\   'callback': 'ale_linters#kotlin#kotlinc#Handle',
\   'lint_file': 1,
\})

I also took a look to the test, but really I can't understand how to verify it :))) So I guess this is just a workaround.

[RyanSquared]

the tests work based on an example output which is usually copy pasted from a terminal, so this change shouldn't affect tests. if you'd like to open a PR and test it out on some actual kotlin project that would be helpful.

[ndtho8205]

I tested it on my kotlin + maven project, so far it works fine. So I make a pull request. Just a really small change :) Btw, my first ever pull request to a project that I really like :))

[hsanson]

@ndtho8205 do you mind telling me which version of kotlinc you are using? trying this PR I cannot get ALE work with Kotlin/Native: 1.3.72. ALE fails with invalid argument: -cp.

Just want to verify if kotlinc outputs all important information only to stderr and not both stderr and stdout before merging this.

[ndtho8205]

Sorry for my late response.

There are two types of Kotlin compiler: kotlinc-jvm and kotlinc-native (you can download them from here). The interface of those two are completely different. ALE linter currently only works on kotlinc-jvm which have argument -cp (--classpath) to include directories for searching java class files. Since you are using kotlinc-native, the ALE will fail.

$ kotlinc -help             #<--- the compiler that I installed (kotlin-compiler-1.3.72.zip)
Usage: kotlinc-jvm <options> <source files>
where possible options include:
  -classpath (-cp) <path>    List of directories and JAR/ZIP archives to search for user class files
  -d <directory|jar>         Destination for generated class files
  -include-runtime           Include Kotlin runtime into the resulting JAR
  -java-parameters           Generate metadata for Java 1.8 reflection on method parameters
  ...

$ ./kotlinc -help             #<--- file extracted from kotlin-native-linux-1.3.72.tar.gz
Usage: kotlinc-native <options> <source files>
where possible options include:
  -g                         Enable emitting debug information
  -enable-assertions (-ea)   Enable runtime assertions in generated code
  -friend-modules <path>     Paths to friend modules
  -generate-no-exit-test-runner (-trn)
  ...

Regarding the outputs of kotlinc, you can check its test cases from here and here. Based on these test cases, I think that all warning and errors will go to stderr.

I think you might need the output of ALEInfo so I include it here :D In this case, ALE with the pull request successfully captured the error output.

(executable check - success) kotlinc
(finished - exit code 0) ['/usr/bin/zsh', '-c', 'cd ''/home/ndtho8205/Desktop/kotlin-maven-example'' && mvn dependency:build-classpath']

<<<OUTPUT STARTS>>>
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------< org.jetbrains.kotlin.examples:dagger-maven-example >---------
[INFO] Building dagger-maven-example 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:build-classpath (default-cli) @ dagger-maven-example ---
[INFO] Dependencies classpath:
/home/ndtho8205/.m2/repository/com/google/dagger/dagger/2.9/dagger-2.9.jar:/home/ndtho8205/.m2/repository/javax/inject/javax.inject/1/javax.inject-1.jar:/home/ndtho8205/.m2/repository/org/jetbrains/kotlin/kotlin-stdlib/1.3.72/kotlin-stdlib-1.3.72.jar:/home/ndtho8205/.m2/repository/org/jetbrains/kotlin/kotlin-stdlib-common/1.3.72/kotlin-stdlib-common-1.3.72.jar:/home/ndtho8205/.m2/repository/org/jetbrains/annotations/13.0/annotations-13.0.jar:/home/ndtho8205/.m2/repository/junit/junit/4.12/junit-4.12.jar:/home/ndtho8205/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.655 s
[INFO] Finished at: 2020-04-19T16:00:55+09:00
[INFO] ------------------------------------------------------------------------
<<<OUTPUT ENDS>>>

(executable check - failure) ktlint
(executable check - failure) kotlin-language-server
(finished - exit code 1) ['/usr/bin/zsh', '-c', 'kotlinc  -cp ''/home/ndtho8205/.m2/repository/com/google/dagger/dagger/2.9/dagger-2.9.jar:/home/ndtho8205/.m2/repository/javax/inject/javax.inject/1/javax.inject-1.jar:/home/ndtho8205/.m2/repository/org/jetbrains/kotlin/kotlin-stdlib/1.3.72/kotlin-stdlib-1.3.72.jar:/home/ndtho8205/.m2/repository/org/jetbrains/kotlin/kotlin-stdlib-common/1.3.72/kotlin-stdlib-common-1.3.72.jar:/home/ndtho8205/.m2/repository/org/jetbrains/annotations/13.0/annotations-13.0.jar:/home/ndtho8205/.m2/repository/junit/junit/4.12/junit-4.12.jar:/home/ndtho8205/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar''  /home/ndtho8205/Desktop/kotlin-maven-example/src/main/kotlin/ ''/home/ndtho8205/Desktop/kotlin-maven-example/src/main/kotlin/CoffeeApp.kt''']

<<<OUTPUT STARTS>>>
src/main/kotlin/CoffeeApp.kt:15:22: error: unresolved reference: DaggerCoffeeApp_Coffee
        val coffee = DaggerCoffeeApp_Coffee.builder().build()
                     ^
src/main/kotlin/CoffeeApp.kt:16:9: error: unresolved reference: offee
        offee.maker().brew()
        ^
<<<OUTPUT ENDS>>>

[hsanson]

Thanks, was able to verify the PR works as expected.