Set `--parser` option in Prettier's fixer (#1620)

* Set `--parser` option in Prettier's fixer
* Add expected `--parser` option to tests
* Disable Prettier `--parser` detection if file extension exists
* Manually default Prettier `--parser` to "babylon"
* Add `--parser` test for TypeScript
* Add tests for Prettier `--parser`
* Add JSON5 to the suggested fixer for Prettier

4 files changed, 160 insertions, 2 deletions

diff --git a/autoload/ale/fix/registry.vim b/autoload/ale/fix/registry.vim
index 7b55acfc..e99b8d2e 100644
--- a/autoload/ale/fix/registry.vim
+++ b/autoload/ale/fix/registry.vim
@@ -51,7 +51,7 @@ let s:default_registry = {
 \   },
 \   'prettier': {
 \       'function': 'ale#fixers#prettier#Fix',
-\       'suggested_filetypes': ['javascript', 'typescript', 'json', 'css', 'scss', 'less', 'markdown', 'graphql', 'vue'],
+\       'suggested_filetypes': ['javascript', 'typescript', 'css', 'less', 'scss', 'json', 'json5', 'graphql', 'markdown', 'vue'],
 \       'description': 'Apply prettier to a file.',
 \   },
 \   'prettier_eslint': {
diff --git a/autoload/ale/fixers/prettier.vim b/autoload/ale/fixers/prettier.vim
index dcc35813..e8f4e92e 100644
--- a/autoload/ale/fixers/prettier.vim
+++ b/autoload/ale/fixers/prettier.vim
@@ -30,8 +30,26 @@ endfunction
 function! ale#fixers#prettier#ApplyFixForVersion(buffer, version_output) abort
     let l:executable = ale#fixers#prettier#GetExecutable(a:buffer)
     let l:options = ale#Var(a:buffer, 'javascript_prettier_options')
-
     let l:version = ale#semver#GetVersion(l:executable, a:version_output)
+    let l:parser = ''
+
+    " Append the --parser flag depending on the current filetype (unless it's
+    " already set in g:javascript_prettier_options).
+    if empty(expand('#' . a:buffer . ':e')) && match(l:options, '--parser') == -1
+        let l:prettier_parsers = ['typescript', 'css', 'less', 'scss', 'json', 'json5', 'graphql', 'markdown', 'vue']
+        let l:parser = 'babylon'
+
+        for l:filetype in split(getbufvar(a:buffer, '&filetype'), '\.')
+            if index(l:prettier_parsers, l:filetype) > -1
+                let l:parser = l:filetype
+                break
+            endif
+        endfor
+    endif
+
+    if !empty(l:parser)
+        let l:options = (!empty(l:options) ? l:options . ' ' : '') . '--parser ' . l:parser
+    endif
 
     " 1.4.0 is the first version with --stdin-filepath
     if ale#semver#GTE(l:version, [1, 4, 0])
diff --git a/test/fixers/test_prettier_fixer_callback.vader b/test/fixers/test_prettier_fixer_callback.vader
index c4f36f52..2018c3a6 100644
--- a/test/fixers/test_prettier_fixer_callback.vader
+++ b/test/fixers/test_prettier_fixer_callback.vader
@@ -95,3 +95,143 @@ Execute(The version number should be cached):
   \     . ' --stdin-filepath %s --stdin',
   \ },
   \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), [])
+
+Execute(Should set --parser based on filetype, TypeScript):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=typescript
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser typescript'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, CSS):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=css
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser css'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, LESS):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=less
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser less'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, SCSS):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=scss
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser scss'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, JSON):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=json
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser json'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, JSON5):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=json5
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser json5'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, GraphQL):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=graphql
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser graphql'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, Markdown):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=markdown
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser markdown'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on filetype, Vue):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=vue
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser vue'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
+
+Execute(Should set --parser based on first filetype of multiple filetypes):
+  call ale#test#SetFilename('../prettier-test-files/testfile')
+
+  set filetype=css.scss
+
+  AssertEqual
+  \ {
+  \   'command': 'cd ' . ale#Escape(expand('%:p:h')) . ' && '
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --parser css'
+  \     . ' --stdin-filepath %s --stdin',
+  \ },
+  \ ale#fixers#prettier#ApplyFixForVersion(bufnr(''), ['1.6.0'])
diff --git a/test/prettier-test-files/testfile b/test/prettier-test-files/testfile
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/prettier-test-files/testfile