Set prettier working directory to where .prettierignore is (#3101)

Prettier does not use `.prettierignore` unless the current directory is the root where the `.prettierignore` file resides.

* Update Prettier tests
* Look for prettierignore to determine project root

4 files changed, 27 insertions, 1 deletions

diff --git a/autoload/ale/fixers/prettier.vim b/autoload/ale/fixers/prettier.vim
index 23120777..e0f4972e 100644
--- a/autoload/ale/fixers/prettier.vim
+++ b/autoload/ale/fixers/prettier.vim
@@ -34,6 +34,21 @@ function! ale#fixers#prettier#ProcessPrettierDOutput(buffer, output) abort
     return a:output
 endfunction
 
+function! ale#fixers#prettier#GetProjectRoot(buffer) abort
+    let l:config = ale#path#FindNearestFile(a:buffer, '.prettierignore')
+
+    if !empty(l:config)
+        return fnamemodify(l:config, ':h')
+    endif
+
+    " Fall back to the directory of the buffer
+    return fnamemodify(bufname(a:buffer), ':p:h')
+endfunction
+
+function! ale#fixers#prettier#CdProjectRoot(buffer) abort
+    return ale#path#CdString(ale#fixers#prettier#GetProjectRoot(a:buffer))
+endfunction
+
 function! ale#fixers#prettier#ApplyFixForVersion(buffer, version) abort
     let l:executable = ale#fixers#prettier#GetExecutable(a:buffer)
     let l:options = ale#Var(a:buffer, 'javascript_prettier_options')
@@ -97,7 +112,7 @@ function! ale#fixers#prettier#ApplyFixForVersion(buffer, version) abort
     " 1.4.0 is the first version with --stdin-filepath
     if ale#semver#GTE(a:version, [1, 4, 0])
         return {
-        \   'command': ale#path#BufferCdString(a:buffer)
+        \   'command': ale#fixers#prettier#CdProjectRoot(a:buffer)
         \       . ale#Escape(l:executable)
         \       . (!empty(l:options) ? ' ' . l:options : '')
         \       . ' --stdin-filepath %s --stdin',
diff --git a/test/fixers/test_prettier_fixer_callback.vader b/test/fixers/test_prettier_fixer_callback.vader
index 1087a160..fdd97df3 100644
--- a/test/fixers/test_prettier_fixer_callback.vader
+++ b/test/fixers/test_prettier_fixer_callback.vader
@@ -297,6 +297,17 @@ Execute(Should set --parser for experimental language, Handlebars):
   \     . ' --stdin-filepath %s --stdin',
   \ }
 
+Execute(Changes to directory where .prettierignore is found):
+  call ale#test#SetFilename('../prettier-test-files/with_prettierignore/src/testfile.js')
+
+  GivenCommandOutput ['1.6.0']
+  AssertFixer
+  \ {
+  \   'command': ale#path#CdString(expand('%:p:h:h'))
+  \     . ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' --stdin-filepath %s --stdin',
+  \ }
+
 Execute(The prettier_d post-processor should permit regular JavaScript content):
   AssertEqual
   \ [
diff --git a/test/prettier-test-files/with_prettierignore/.prettierignore b/test/prettier-test-files/with_prettierignore/.prettierignore
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/prettier-test-files/with_prettierignore/.prettierignore
diff --git a/test/prettier-test-files/with_prettierignore/src/testfile.js b/test/prettier-test-files/with_prettierignore/src/testfile.js
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/prettier-test-files/with_prettierignore/src/testfile.js