refactor: add codefmt#formatterhelpers#ResolveFlagToArray (#138)

Refactor some common boilerplate so that it's easier to apply this logic
to executables and options across all plugins. Implemented in prettier
and zprint for starters, with no functional changes to either plugin.

Author: agriffis

autoload/codefmt/formatterhelpers.vim

@@ -13,6 +13,9 @@
 " limitations under the License.
 
 
+let s:plugin = maktaba#plugin#Get('codefmt')
+
+
 ""
 " @public
 " Format lines in the current buffer via a formatter invoked by {cmd}, which
@@ -31,6 +34,7 @@ function! codefmt#formatterhelpers#Format(cmd) abort
   call maktaba#buffer#Overwrite(1, line('$'), l:formatted)
 endfunction
 
+
 ""
 " @public
 " Attempt to format a range of lines from {startline} to {endline} in the
@@ -62,3 +66,44 @@ function! codefmt#formatterhelpers#AttemptFakeRangeFormatting(
 
   call maktaba#buffer#Overwrite(1, line('$'), l:full_formatted)
 endfunction
+
+
+""
+" @public
+" Resolve a flag (function, string or array) to a normalized array, with special
+" handling to convert a spaceless string to a single-element array. This is the
+" common case for executables, and more importantly, is backward-compatible for
+" existing user settings.
+"
+" @throws WrongType if the flag doesn't resolve to a string or array
+function! codefmt#formatterhelpers#ResolveFlagToArray(flag_name) abort
+  let l:FlagFn = s:plugin.Flag(a:flag_name)
+  if maktaba#value#IsFuncref(l:FlagFn)
+    let l:value = maktaba#function#Call(l:FlagFn)
+  else
+    let l:value = l:FlagFn
+  endif
+
+  " After (conditionally) calling the function, the resulting value should be
+  " either a list that we can use directly, or a string that we can treat as
+  " a single-element list, mainly for backward compatibility.
+  if maktaba#value#IsString(l:value)
+    if l:value =~ '\s'
+      " Uh oh, there are spaces in the string. Rather than guessing user intent
+      " with shell quoting and word splitting, handle this (hopefully unusual)
+      " case by telling them to update their configuration.
+      throw maktaba#error#WrongType(
+            \ '%s flag is a string with spaces, please make it a list. ' .
+            \ 'Resolved value was: %s',
+            \ a:flag_name, l:value)
+    endif
+    " Convert spaceless string to single-element list.
+    let l:value = [l:value]
+  elseif !maktaba#value#IsList(l:value)
+    throw maktaba#error#WrongType(
+          \ '%s flag should be a list after calling. Found %s',
+          \ a:flag_name, maktaba#value#TypeName(l:value))
+  endif
+
+  return l:value
+endfunction

autoload/codefmt/prettier.vim

@@ -16,7 +16,7 @@
 let s:plugin = maktaba#plugin#Get('codefmt')
 
 " See https://prettier.io for a list of supported file types.
-let s:supported_filetypes = ['javascript', 'markdown', 'html', 'css', 'yaml', 
+let s:supported_filetypes = ['javascript', 'markdown', 'html', 'css', 'yaml',
       \ 'jsx', 'less', 'scss', 'mdx', 'vue']
 
 
@@ -30,7 +30,9 @@ function! codefmt#prettier#GetFormatter() abort
           \ 'and configure the prettier_executable flag'}
 
   function l:formatter.IsAvailable() abort
-    return executable(s:plugin.Flag('prettier_executable'))
+    let l:cmd = codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'prettier_executable')
+    return !empty(l:cmd) && executable(l:cmd[0])
   endfunction
 
   function l:formatter.AppliesToBuffer() abort
@@ -42,17 +44,8 @@ function! codefmt#prettier#GetFormatter() abort
   " @flag(prettier_executable), only targeting the range between {startline} and
   " {endline}.
   function l:formatter.FormatRange(startline, endline) abort
-    let l:Prettier_options = s:plugin.Flag('prettier_options')
-    if type(l:Prettier_options) is# type([])
-      let l:prettier_options = l:Prettier_options
-    elseif maktaba#value#IsCallable(l:Prettier_options)
-      let l:prettier_options = maktaba#function#Call(l:Prettier_options)
-    else
-      throw maktaba#error#WrongType(
-          \ 'prettier_options flag must be list or callable. Found %s',
-          \ string(l:Prettier_options))
-    endif
-    let l:cmd = [s:plugin.Flag('prettier_executable'), '--stdin', '--no-color']
+    let l:cmd = codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'prettier_executable') + ['--stdin', '--no-color']
 
     " prettier is able to automatically choose the best parser if the filepath
     " is provided. Otherwise, fall back to the previous default: babylon.
@@ -74,7 +67,9 @@ function! codefmt#prettier#GetFormatter() abort
     let l:lines_end = join(l:lines[0 : a:endline - 1], "\n")
     call extend(l:cmd, ['--range-end', string(strchars(l:lines_end))])
 
-    call extend(l:cmd, l:prettier_options)
+    call extend(l:cmd, codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'prettier_options'))
+
     try
       let l:result = maktaba#syscall#Create(l:cmd).WithStdin(l:input).Call()
       let l:formatted = split(l:result.stdout, "\n")

autoload/codefmt/zprint.vim

@@ -38,7 +38,9 @@ function! codefmt#zprint#GetFormatter() abort
         \ 'and configure the zprint_executable flag'}
 
   function l:formatter.IsAvailable() abort
-    return executable(s:plugin.Flag('zprint_executable'))
+    let l:cmd = codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'zprint_executable')
+    return !empty(l:cmd) && executable(l:cmd[0])
   endfunction
 
   function l:formatter.AppliesToBuffer() abort
@@ -50,25 +52,15 @@ function! codefmt#zprint#GetFormatter() abort
   " @flag(zprint_executable), only targeting the range between {startline} and
   " {endline}.
   function l:formatter.FormatRange(startline, endline) abort
-    " Must be upper-cased to call as a function
-    let l:ZprintOptions = s:plugin.Flag('zprint_options')
-    if type(l:ZprintOptions) is# type([])
-      " Assign upper-case to lower-case
-      let l:zprint_options = l:ZprintOptions
-    elseif maktaba#value#IsCallable(l:ZprintOptions)
-      " Call upper-case to assign lower-case
-      let l:zprint_options = maktaba#function#Call(l:ZprintOptions)
-    else
-      throw maktaba#error#WrongType(
-            \ 'zprint_options flag must be list or callable. Found %s',
-            \ string(l:ZprintOptions))
-    endif
-    let l:cmd_args = [s:plugin.Flag('zprint_executable')]
-    call extend(l:cmd_args, l:zprint_options)
+    let l:exe = codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'zprint_executable')
+    let l:opts = codefmt#formatterhelpers#ResolveFlagToArray(
+          \ 'zprint_options')
 
     " Prepare the syscall, changing to the containing directory in case the user
     " has configured {:search-config? true} in ~/.zprintrc
-    let l:cmd = maktaba#syscall#Create(l:cmd_args).WithCwd(expand('%:p:h'))
+    let l:cmd = maktaba#syscall#Create(l:exe + l:opts).WithCwd(expand('%:p:h'))
+
     " zprint does not support range formatting yet:
     " https://github.com/kkinnear/zprint/issues/122
     " This fake range formatting works well for top-level forms, although it's