12 files changed, 120 insertions, 12 deletions
diff --git a/README.md b/README.md
index 3a793d75..e5f5a579 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@ name. That seems to be the fairest way to arrange this table.
 | Haskell | [ghc](https://www.haskell.org/ghc/), [hlint](https://hackage.haskell.org/package/hlint), [hdevtools](https://hackage.haskell.org/package/hdevtools) |
 | HTML | [HTMLHint](http://htmlhint.com/), [proselint](http://proselint.com/), [tidy](http://www.html-tidy.org/) |
 | Java | [javac](http://www.oracle.com/technetwork/java/javase/downloads/index.html) |
-| JavaScript | [eslint](http://eslint.org/), [jscs](http://jscs.info/), [jshint](http://jshint.com/), [flow](https://flowtype.org/), [standard](http://standardjs.com/)
+| JavaScript | [eslint](http://eslint.org/), [jscs](http://jscs.info/), [jshint](http://jshint.com/), [flow](https://flowtype.org/), [standard](http://standardjs.com/), [xo](https://github.com/sindresorhus/xo)
 | JSON | [jsonlint](http://zaa.ch/jsonlint/) |
 | LaTeX | [chktex](http://www.nongnu.org/chktex/), [lacheck](https://www.ctan.org/pkg/lacheck) |
 | Lua | [luacheck](https://github.com/mpeterv/luacheck) |
@@ -95,6 +95,7 @@ name. That seems to be the fairest way to arrange this table.
 | Pug | [pug-lint](https://github.com/pugjs/pug-lint) |
 | Puppet | [puppet](https://puppet.com), [puppet-lint](https://puppet-lint.com) |
 | Python | [flake8](http://flake8.pycqa.org/en/latest/), [mypy](http://mypy-lang.org/), [pylint](https://www.pylint.org/) |
+| ReasonML | [merlin](https://github.com/the-lambda-church/merlin) see `:help ale-integration-reason-merlin` for configuration instructions
 | reStructuredText | [proselint](http://proselint.com/)|
 | RPM spec | [rpmlint](https://github.com/rpm-software-management/rpmlint) (disabled by default; see `:help ale-integration-spec`) |
 | Ruby | [reek](https://github.com/troessner/reek), [rubocop](https://github.com/bbatsov/rubocop), [ruby](https://www.ruby-lang.org) |
diff --git a/ale_linters/reason/merlin.vim b/ale_linters/reason/merlin.vim
new file mode 100644
index 00000000..7bef7df8
--- /dev/null
+++ b/ale_linters/reason/merlin.vim
@@ -0,0 +1,17 @@
+" Author: Andrey Popp -- @andreypopp
+" Description: Report errors in ReasonML code with Merlin
+
+if !exists('g:merlin')
+    finish
+endif
+
+function! ale_linters#reason#merlin#Handle(buffer, lines) abort
+    return merlin#ErrorLocList()
+endfunction
+
+call ale#linter#Define('reason', {
+\   'name': 'merlin',
+\   'executable': 'ocamlmerlin',
+\   'command': 'true',
+\   'callback': 'ale_linters#reason#merlin#Handle',
+\})
diff --git a/autoload/ale.vim b/autoload/ale.vim
index b911c215..b9cd648f 100644
--- a/autoload/ale.vim
+++ b/autoload/ale.vim
@@ -113,5 +113,5 @@ endfunction
 function! ale#Var(buffer, variable_name) abort
     let l:full_name = 'ale_' . a:variable_name
 
-    return getbufvar(a:buffer, l:full_name, g:[l:full_name])
+    return getbufvar(str2nr(a:buffer), l:full_name, g:[l:full_name])
 endfunction
diff --git a/autoload/ale/debugging.vim b/autoload/ale/debugging.vim
index 60c1b37c..f42c9e82 100644
--- a/autoload/ale/debugging.vim
+++ b/autoload/ale/debugging.vim
@@ -51,12 +51,20 @@ endfunction
 function! s:EchoLinterVariables(variable_list) abort
     for l:key in a:variable_list
         echom 'let g:' . l:key . ' = ' . string(g:[l:key])
+
+        if has_key(b:, l:key)
+            echom 'let b:' . l:key . ' = ' . string(b:[l:key])
+        endif
     endfor
 endfunction
 
 function! s:EchoGlobalVariables() abort
     for l:key in s:global_variable_list
         echom 'let g:' . l:key . ' = ' . string(get(g:, l:key, v:null))
+
+        if has_key(b:, l:key)
+            echom 'let b:' . l:key . ' = ' . string(b:[l:key])
+        endif
     endfor
 endfunction
 
diff --git a/autoload/ale/sign.vim b/autoload/ale/sign.vim
index e002f584..0e0250bf 100644
--- a/autoload/ale/sign.vim
+++ b/autoload/ale/sign.vim
@@ -169,6 +169,12 @@ endfunction
 
 " This function will set the signs which show up on the left.
 function! ale#sign#SetSigns(buffer, loclist) abort
+    if !bufexists(str2nr(a:buffer))
+        " Stop immediately when attempting to set signs for a buffer which
+        " does not exist.
+        return
+    endif
+
     " Find the current markers
     let l:current_sign_list = ale#sign#FindCurrentSigns(a:buffer)
 
diff --git a/custom-checks b/custom-checks
index 440dafe5..37d2840c 100755
--- a/custom-checks
+++ b/custom-checks
@@ -44,24 +44,26 @@ fi
 
 shopt -s globstar
 
-directory="$1"
+directories=("$@")
 
 check_errors() {
     regex="$1"
     message="$2"
 
-    for match in $(
-        grep -n "$regex" "$directory"/**/*.vim \
-        | grep -o '^[^:]\+:[0-9]\+' \
-        | sed 's:^\./::'
-    ); do
-        RETURN_CODE=1
-        echo "$match $message"
+    for directory in "${directories[@]}"; do
+        while IFS= read -r match; do
+            RETURN_CODE=1
+            echo "$match $message"
+        done < <(grep -n "$regex" "$directory"/**/*.vim \
+            | grep -o '^[^:]\+:[0-9]\+' \
+            | sed 's:^\./::')
     done
 }
 
 if (( FIX_ERRORS )); then
-    sed -i "s/^\(function.*)\) *$/\1 abort/" "$directory"/**/*.vim
+    for directory in "${directories[@]}"; do
+        sed -i "s/^\(function.*)\) *$/\1 abort/" "$directory"/**/*.vim
+    done
 fi
 
 check_errors \
diff --git a/doc/ale-reasonml.txt b/doc/ale-reasonml.txt
new file mode 100644
index 00000000..3d411485
--- /dev/null
+++ b/doc/ale-reasonml.txt
@@ -0,0 +1,15 @@
+===============================================================================
+ALE ReasonML Integration                                 *ale-reasonml-options*
+
+
+-------------------------------------------------------------------------------
+merlin                                                    *ale-reasonml-merlin*
+
+  To use merlin linter for ReasonML source code you need to make sure Merlin
+  for Vim is correctly configured. See the corresponding Merlin wiki page for
+  detailed instructions
+  (https://github.com/the-lambda-church/merlin/wiki/vim-from-scratch).
+
+
+-------------------------------------------------------------------------------
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:
diff --git a/doc/ale.txt b/doc/ale.txt
index 7f391964..0e9ad35b 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -153,6 +153,7 @@ The following languages and tools are supported.
 * Pug: 'pug-lint'
 * Puppet: 'puppet', 'puppet-lint'
 * Python: 'flake8', 'mypy', 'pylint'
+* ReasonML: 'merlin'
 * reStructuredText: 'proselint'
 * RPM spec: 'spec'
 * Rust: 'rustc' (see |ale-integration-rust|)
diff --git a/plugin/ale.vim b/plugin/ale.vim
index b6f6f296..0e8c369f 100644
--- a/plugin/ale.vim
+++ b/plugin/ale.vim
@@ -181,7 +181,15 @@ function! ALEInitAuGroups() abort
     augroup ALERunOnFiletypeChangeGroup
         autocmd!
         if g:ale_enabled && g:ale_lint_on_filetype_changed
-            autocmd FileType * call ale#Queue(300, 'lint_file')
+            " Set the filetype after a buffer is opened or read.
+            autocmd BufEnter,BufRead * let b:ale_original_filetype = &filetype
+            " Only start linting if the FileType actually changes after
+            " opening a buffer. The FileType will fire when buffers are opened.
+            autocmd FileType *
+            \   if has_key(b:, 'ale_original_filetype')
+            \   && b:ale_original_filetype !=# expand('<amatch>')
+            \|      call ale#Queue(300, 'lint_file')
+            \|  endif
         endif
     augroup END
 
diff --git a/test/sign/test_sign_placement.vader b/test/sign/test_sign_placement.vader
index 396ef5c4..518e1b81 100644
--- a/test/sign/test_sign_placement.vader
+++ b/test/sign/test_sign_placement.vader
@@ -132,3 +132,6 @@ Execute(Loclist items with sign_id values should be kept):
   \   ['16', '1000004', 'ALEErrorSign'],
   \ ],
   \ ParseSigns()
+
+Execute(No excpetions should be thrown when setting signs for invalid buffers):
+  call ale#sign#SetSigns(123456789, [{'lnum': 15, 'col': 2, 'type': 'W', 'text': 'e'}])
diff --git a/test/test_ale_info.vader b/test/test_ale_info.vader
index d5a8ed62..83d32cb0 100644
--- a/test/test_ale_info.vader
+++ b/test/test_ale_info.vader
@@ -37,6 +37,7 @@ Before:
   let g:command_header = "\n  Command History:\n"
 
 After:
+  unlet! b:ale_linters
   unlet! g:output
   unlet! g:globals_string
   unlet! g:command_header
@@ -45,6 +46,7 @@ After:
   unlet! g:ale_testft_testlinter1_foo
   unlet! g:ale_testft_testlinter1_bar
   unlet! g:ale_testft2_testlinter2_foo
+  unlet! b:ale_testft2_testlinter2_foo
   unlet! g:ale_testft2_testlinter2_bar
 
 Given nolintersft (Empty buffer with no linters):
@@ -60,6 +62,26 @@ Execute (ALEInfo with no linters should return the right output):
               \" . g:globals_string . g:command_header, g:output
 
 Given (Empty buffer with no filetype):
+Execute (ALEInfo should return buffer-local global ALE settings):
+  let b:ale_linters = {'x': ['y']}
+  let g:globals_string = substitute(
+  \ g:globals_string,
+  \ 'let g:ale_linters = {}',
+  \ "let g:ale_linters = {}\nlet b:ale_linters = {'x': ['y']}",
+  \ ''
+  \)
+
+  redir => g:output
+  silent ALEInfo
+  redir END
+  AssertEqual "\n
+              \ Current Filetype: \n
+              \Available Linters: []\n
+              \  Enabled Linters: []\n
+              \ Linter Variables:\n
+              \" . g:globals_string . g:command_header, g:output
+
+Given (Empty buffer with no filetype):
 Execute (ALEInfo with no filetype should return the right output):
   redir => g:output
   silent ALEInfo
@@ -167,6 +189,26 @@ Execute (ALEInfo should return appropriately named global variables):
               \ . g:globals_string . g:command_header, g:output
 
 Given testft.testft2 (Empty buffer with two filetypes):
+Execute (ALEInfo should buffer-local linter variables):
+  let g:ale_testft2_testlinter2_foo = 123
+  let b:ale_testft2_testlinter2_foo = 456
+
+  call ale#linter#Define('testft', g:testlinter1)
+  call ale#linter#Define('testft2', g:testlinter2)
+  redir => g:output
+  silent ALEInfo
+  redir END
+  AssertEqual "\n
+              \ Current Filetype: testft.testft2\n
+              \Available Linters: ['testlinter1', 'testlinter2']\n
+              \  Enabled Linters: ['testlinter1', 'testlinter2']\n
+              \ Linter Variables:\n
+              \\n
+              \let g:ale_testft2_testlinter2_foo = 123\n
+              \let b:ale_testft2_testlinter2_foo = 456"
+              \ . g:globals_string . g:command_header, g:output
+
+Given testft.testft2 (Empty buffer with two filetypes):
 Execute (ALEInfo should return command history):
   let g:ale_buffer_info[bufnr('%')] = {
   \ 'history': [
diff --git a/test/test_ale_var.vader b/test/test_ale_var.vader
index aee8e048..576b403f 100644
--- a/test/test_ale_var.vader
+++ b/test/test_ale_var.vader
@@ -12,5 +12,10 @@ Execute(ale#Var should return buffer overrides):
 
   AssertEqual 'def', ale#Var(bufnr(''), 'some_variable')
 
+Execute(ale#Var should return buffer overrides for buffer numbers as strings):
+  let b:ale_some_variable = 'def'
+
+  AssertEqual 'def', ale#Var(string(bufnr('')), 'some_variable')
+
 Execute(ale#Var should throw exceptions for undefined variables):
   AssertThrows call ale#Var(bufnr(''), 'undefined_variable_name')