Close #3285 - lint_file is now dynamic

`lint_file` can now be computed dynamically with a callback function,
which can return a deferred result, as per `ale#command#Run`. This
allows linters to dynamically switch between checking files on disk,
or checking code on the fly.

Some tests have been fixed on Windows.

5 files changed, 154 insertions, 15 deletions

diff --git a/test/smoke_test.vader b/test/smoke_test.vader
index 53e08a8d..0b126cc6 100644
--- a/test/smoke_test.vader
+++ b/test/smoke_test.vader
@@ -1,8 +1,10 @@
 Before:
+  Save g:ale_enabled
   Save g:ale_set_lists_synchronously
   Save g:ale_buffer_info
   Save &shell
 
+  let g:ale_enabled = 1
   let g:ale_buffer_info = {}
   let g:ale_set_lists_synchronously = 1
 
diff --git a/test/test_computed_lint_file_values.vader b/test/test_computed_lint_file_values.vader
new file mode 100644
index 00000000..399e96fe
--- /dev/null
+++ b/test/test_computed_lint_file_values.vader
@@ -0,0 +1,134 @@
+Before:
+  Save g:ale_enabled
+  Save g:ale_run_synchronously
+  Save g:ale_set_lists_synchronously
+  Save g:ale_buffer_info
+
+  let g:ale_enabled = 1
+  let g:ale_buffer_info = {}
+  let g:ale_run_synchronously = 1
+  let g:ale_set_lists_synchronously = 1
+
+  function! TestCallback(buffer, output)
+    " Windows adds extra spaces to the text from echo.
+    return [{
+    \ 'lnum': 2,
+    \ 'col': 3,
+    \ 'text': 'testlinter1',
+    \}]
+  endfunction
+  function! TestCallback2(buffer, output)
+    " Windows adds extra spaces to the text from echo.
+    return [{
+    \ 'lnum': 1,
+    \ 'col': 3,
+    \ 'text': 'testlinter2',
+    \}]
+  endfunction
+  function! TestCallback3(buffer, output)
+    " Windows adds extra spaces to the text from echo.
+    return [{
+    \ 'lnum': 3,
+    \ 'col': 3,
+    \ 'text': 'testlinter3',
+    \}]
+  endfunction
+
+  " These two linters computer their lint_file values after running commands.
+  call ale#linter#Define('foobar', {
+  \ 'name': 'testlinter1',
+  \ 'callback': 'TestCallback',
+  \ 'executable': has('win32') ? 'cmd' : 'echo',
+  \ 'command': has('win32') ? 'echo foo bar' : '/bin/sh -c ''echo foo bar''',
+  \ 'lint_file': {b -> ale#command#Run(b, 'echo', {-> 1})},
+  \})
+  call ale#linter#Define('foobar', {
+  \ 'name': 'testlinter2',
+  \ 'callback': 'TestCallback2',
+  \ 'executable': has('win32') ? 'cmd' : 'echo',
+  \ 'command': has('win32') ? 'echo foo bar' : '/bin/sh -c ''echo foo bar''',
+  \ 'lint_file': {b -> ale#command#Run(b, 'echo', {-> ale#command#Run(b, 'echo', {-> 1})})},
+  \})
+  " This one directly computes the result.
+  call ale#linter#Define('foobar', {
+  \ 'name': 'testlinter3',
+  \ 'callback': 'TestCallback3',
+  \ 'executable': has('win32') ? 'cmd' : 'echo',
+  \ 'command': has('win32') ? 'echo foo bar' : '/bin/sh -c ''echo foo bar''',
+  \ 'lint_file': {b -> 1},
+  \})
+
+  let g:filename = tempname()
+  call writefile([], g:filename)
+  call ale#test#SetFilename(g:filename)
+
+After:
+  delfunction TestCallback
+
+  call ale#engine#Cleanup(bufnr(''))
+  Restore
+  call ale#linter#Reset()
+
+  " Items and markers, etc.
+  call setloclist(0, [])
+  call clearmatches()
+  call ale#sign#Clear()
+
+  if filereadable(g:filename)
+    call delete(g:filename)
+  endif
+
+  unlet g:filename
+
+Given foobar(A file with some lines):
+  foo
+  bar
+  baz
+
+Execute(lint_file results where the result is eventually computed should be run):
+  call ale#Queue(0, 'lint_file')
+  call ale#test#FlushJobs()
+
+  AssertEqual
+  \ [
+  \   {
+  \     'bufnr': bufnr('%'),
+  \     'lnum': 1,
+  \     'vcol': 0,
+  \     'col': 3,
+  \     'text': 'testlinter2',
+  \     'type': 'E',
+  \     'nr': -1,
+  \     'pattern': '',
+  \     'valid': 1,
+  \   },
+  \   {
+  \     'bufnr': bufnr('%'),
+  \     'lnum': 2,
+  \     'vcol': 0,
+  \     'col': 3,
+  \     'text': 'testlinter1',
+  \     'type': 'E',
+  \     'nr': -1,
+  \     'pattern': '',
+  \     'valid': 1,
+  \   },
+  \   {
+  \     'bufnr': bufnr('%'),
+  \     'lnum': 3,
+  \     'vcol': 0,
+  \     'col': 3,
+  \     'text': 'testlinter3',
+  \     'type': 'E',
+  \     'nr': -1,
+  \     'pattern': '',
+  \     'valid': 1,
+  \   },
+  \ ],
+  \ ale#test#GetLoclistWithoutModule()
+
+Execute(Linters where lint_file eventually evaluates to 1 shouldn't be run if we don't want to run them):
+  call ale#Queue(0, '')
+  call ale#test#FlushJobs()
+
+  AssertEqual [], ale#test#GetLoclistWithoutModule()
diff --git a/test/test_deferred_command_string.vader b/test/test_deferred_command_string.vader
index 026be6fe..173b6bb2 100644
--- a/test/test_deferred_command_string.vader
+++ b/test/test_deferred_command_string.vader
@@ -12,7 +12,7 @@ Before:
   call ale#linter#Define('foobar', {
   \ 'name': 'lint_file_linter',
   \ 'callback': 'LintFileCallback',
-  \ 'executable': 'echo',
+  \ 'executable': has('win32') ? 'cmd' : 'echo',
   \ 'command': {b -> ale#command#Run(b, 'echo', {-> ale#command#Run(b, 'echo', {-> 'foo'})})},
   \ 'read_buffer': 0,
   \})
@@ -28,7 +28,7 @@ After:
 
 Given foobar (Some imaginary filetype):
 Execute(It should be possible to compute an executable to check based on the result of commands):
-  AssertLinter 'echo', 'foo'
+  AssertLinter has('win32') ? 'cmd' : 'echo', 'foo'
 
   ALELint
   call ale#test#FlushJobs()
@@ -40,7 +40,7 @@ Execute(It should be possible to compute an executable to check based on the res
 Execute(It handle the deferred command failing):
   let g:ale_emulate_job_failure = 1
 
-  AssertLinter 'echo', 0
+  AssertLinter has('win32') ? 'cmd' : 'echo', 0
 
   ALELint
   call ale#test#FlushJobs()
diff --git a/test/test_linter_defintion_processing.vader b/test/test_linter_defintion_processing.vader
index 2c85299b..d000b158 100644
--- a/test/test_linter_defintion_processing.vader
+++ b/test/test_linter_defintion_processing.vader
@@ -174,7 +174,7 @@ Execute(PreProcess should process the lint_file option correctly):
   \}
 
   AssertThrows call ale#linter#PreProcess('testft', g:linter)
-  AssertEqual '`lint_file` must be `0` or `1`', g:vader_exception
+  AssertEqual '`lint_file` must be `0`, `1`, or a Function', g:vader_exception
 
   let g:linter.lint_file = 0
 
@@ -185,14 +185,17 @@ Execute(PreProcess should process the lint_file option correctly):
   let g:linter.lint_file = 1
 
   AssertEqual 1, ale#linter#PreProcess('testft', g:linter).lint_file
-  " The default for read_buffer should change to 0 when lint_file is 1.
-  AssertEqual 0, ale#linter#PreProcess('testft', g:linter).read_buffer
+  " The default for read_buffer should still be 1
+  AssertEqual 1, ale#linter#PreProcess('testft', g:linter).read_buffer
 
   let g:linter.read_buffer = 1
 
-  " We shouldn't be able to set both options to 1 at the same time.
-  AssertThrows call ale#linter#PreProcess('testft', g:linter)
-  AssertEqual 'Only one of `lint_file` or `read_buffer` can be `1`', g:vader_exception
+  " We should be able to set `read_buffer` and `lint_file` at the same time.
+  AssertEqual 1, ale#linter#PreProcess('testft', g:linter).read_buffer
+
+  let g:linter.lint_file = function('type')
+
+  Assert type(ale#linter#PreProcess('testft', g:linter).lint_file) is v:t_func
 
 Execute(PreProcess should set a default value for lint_file):
   let g:linter = {
diff --git a/test/test_swiftlint_executable_detection.vader b/test/test_swiftlint_executable_detection.vader
index dfd4930b..ac83ff8f 100644
--- a/test/test_swiftlint_executable_detection.vader
+++ b/test/test_swiftlint_executable_detection.vader
@@ -23,22 +23,22 @@ Execute(React Native apps using CocoaPods should take precedence over the defaul
   call ale#test#SetFilename('swiftlint-test-files/react-native/testfile.swift')
 
   AssertEqual
-  \ ale#path#Simplify(g:dir . '/swiftlint-test-files/react-native/ios/Pods/SwiftLint/swiftlint'),
-  \ ale_linters#swift#swiftlint#GetExecutable(bufnr(''))
+  \ tolower(ale#path#Simplify(g:dir . '/swiftlint-test-files/react-native/ios/Pods/SwiftLint/swiftlint')),
+  \ tolower(ale_linters#swift#swiftlint#GetExecutable(bufnr('')))
 
 Execute(CocoaPods installation should take precedence over the default executable):
   call ale#test#SetFilename('swiftlint-test-files/cocoapods/testfile.swift')
 
   AssertEqual
-  \ ale#path#Simplify(g:dir . '/swiftlint-test-files/cocoapods/Pods/SwiftLint/swiftlint'),
-  \ ale_linters#swift#swiftlint#GetExecutable(bufnr(''))
+  \ tolower(ale#path#Simplify(g:dir . '/swiftlint-test-files/cocoapods/Pods/SwiftLint/swiftlint')),
+  \ tolower(ale_linters#swift#swiftlint#GetExecutable(bufnr('')))
 
 Execute(Top level CocoaPods installation should take precedence over React Native installation):
   call ale#test#SetFilename('swiftlint-test-files/cocoapods-and-react-native/testfile.swift')
 
   AssertEqual
-  \ ale#path#Simplify(g:dir . '/swiftlint-test-files/cocoapods-and-react-native/Pods/SwiftLint/swiftlint'),
-  \ ale_linters#swift#swiftlint#GetExecutable(bufnr(''))
+  \ tolower(ale#path#Simplify(g:dir . '/swiftlint-test-files/cocoapods-and-react-native/Pods/SwiftLint/swiftlint')),
+  \ tolower(ale_linters#swift#swiftlint#GetExecutable(bufnr('')))
 
 Execute(use-global should override other versions):
   let g:ale_swift_swiftlint_use_global = 1