Fixing Middleman-spellcheck

by Wojciech Adam Koszek   ⋅   Jun 20, 2015   ⋅   Menlo Park, CA

I liked Middleman for writing my website, I went and fixed up the spell-checking plugin. This piece explains some things step-by-step on how fixing some open source stuff looks like.

Sometimes when you make a change to the software, it is interesting to predict how long will such change take. Fixing Middleman-spellcheck was initially only about letting myself to select words which I would consider correct and do it from within the front-matter of each Middleman’s article files. It ended up taking more than I anticipated, and below is short description on what went wrong.

Middleman plugin infrastructure lets one to run a filter on several stages of the build process, and Middleman-spellcheck runs at the end, once all files are converted from .md to .html files.

Unfortunately the moment I run Middleman with Middleman-spellcheck enabled I got many, many valid words recognized as misspelled words.

Problem appears to be reported as issue #7.

I think no easy model exists for fixing the source code of Gems installed in a system-wide location.

I ended up cloning the repository of the project:

$ cd /w/repos
$ git clone

and basically doing:

$ sudo bash
# cd /Library/Ruby/Gems/2.0.0/gems
# mv middleman-spellcheck-0.7.5 middleman-spellcheck-0.7.5.old
# ln -s /w/repos/middleman-spellcheck middleman-spellcheck-0.7.5

since I don’t know any better way to point Middleman to use a different Gem. Middleman-spell is structured more or less like that:

[wkoszek-macbook:/w/repos/middleman-spellcheck] wk% tree
├── Gemfile
├── LICENSE.txt
├── Rakefile
├── lib
│   ├── middleman-spellcheck
│   │   ├── extension.rb
│   │   ├── spellchecker.rb
│   │   └── version.rb
│   ├── middleman-spellcheck.rb
│   └── middleman_extension.rb
├── middleman-spellcheck.gemspec
└── spec
    └── lib
	└── middleman-spellcheck
	    └── spellcheck_spec.rb

22 directories, 31 files

extension.rb is the Middleman-specific code, while spellcheck.rb is where interaction with Aspell is present.

Here’s our wolf:

  def self.query(text, lang='en')
    result = `echo "#{text}" | #{@@aspell_path} -a -l #{lang}`
    raise 'Aspell command not found' unless result
    new_result = result.split("\n")
    new_result[1..-1] || []

My first guess is was that #{text} has some quotes ", but it wasn’t it. The way I try to attack the problem is always with the simplified use case. The pattern is: find for which input the program is failing and try to reproduce such failure. In my case I have 145 .md files, but managed to find one which is fairly short.

Here are the errors:

spellcheck  Running spell checker for /blog/2012/12/15/book-the-22-laws-of-marketing/
    misspell  The word 'nd' is misspelled
    misspell  The word 'entirely' is misspelled
    misspell  The word 'want' is misspelled
    misspell  The word 'think' is misspelled
    misspell  The word 'to' is misspelled
    misspell  The word 'numbers' is misspelled
    misspell  The word 'has' is misspelled

While nd is probably correctly classified as a problem, “want” and “think” are not. It was time to get more visibility:

diff --git a/lib/middleman-spellcheck/spellchecker.rb b/lib/middleman-spellcheck/spellchecker.rb
index 05a48d1..b82c33a 100644
--- a/lib/middleman-spellcheck/spellchecker.rb
+++ b/lib/middleman-spellcheck/spellchecker.rb
@@ -23,9 +23,12 @@ class Spellchecker
     if @@aspell_cmdargs != ""
       args = @@aspell_cmdargs
-    result = `echo "#{text}" | #{@@aspell_path} #{@@aspell_cmdargs}`
+    print "ARGS:\n#{args}"
+    print "TEXT:\n#{text}\n"
+    result = `echo "#{text}" | #{@@aspell_path} #{args}`
     raise 'Aspell command not found' unless result
     new_result = result.split("\n")
+    print "RESULT:\n#{new_result}\n"
     new_result[1..-1] || []

Unfortunately it wasn’t enough. The problem with middleman-spellcheck is that it used no temporary variables for intermediate results. I had to modify code some more to actually understand what’s wrong:

@@ -40,10 +44,21 @@ class Spellchecker
     # the reported mispelled word is actually a correct word.
     # see:
     words   = text.split(/[^A-Za-z’']+/).join(" ")
-    results = query(words, lang).map do |query_result|
+    results_raw = query(words, lang)
+    results = do |query_result|

+    ww = words.split(" ")
+    print "Words count: ", ww.length
+    for i in 0..35 do
+      word = ww[i]
+      ret = results[i]
+      print "Word:\t#{word}\tRet:\t#{ret}\n"
+    end

Note that what I’m doing is essentially a very bad looking hack over the code, but without it, I simply can’t actually see which word caused the problem to aspell.

I compared the sizes of results[] and words[] and basically saw that there are more results than words. It means that somewhere within my text is a data that aspell sees as 2 words.

For the purposes of debugging I also modified the input file, so that it only had 1 paragraph and was throwing 1 error.

After adding instrumentation, I got this:

Word:	here	Ret:	true
Word:	weren’t	Ret:	false
Word:	entirely	Ret:	true
Word:	due	Ret:	true

Voila. The apostrophe (Hex 2109) seems guilty. We test by hand:

wkoszek-macbook:/w/me] wk% aspell -a
@(#) International Ispell Version 3.1.20 (but really Aspell
& weren 30 0: Warren, warren, wherein, whereon, Wren, ween, were, wren,
Wezen, Webern, we're, wearing, weeny, where, Verne, wen, weren't, Green,
green, preen, wearer, Vern, Ware, ware, warn, wean, when, wire, wore, worn

Here’s our problem. Middleman takes care of the Web typography and converts character ‘ to character ’ internally. So HTML files, which middleman-spellcheck sees use the “aspell unfriendly” version. This causes our problems.

There were several issues with the original code, and I suggested couple of improvements, so that further debugging efforts were easier. In my fix the code passes individual words to aspell, so that in case of problems, we can see what’s going on. I added a “debug” keyword, and couple of others.

My original pull request

UPDATE 2015-06-21: Middleman-spellcheck author merged my pull request, so hopefully you shouldn’t encounter additional problems.

Right now all of my 145 files can be correctly checked with middleman-spellcheck.

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About the author: I'm Wojciech Adam Koszek. I like software, business and design. Poland native. In Bay Area since 2010.   More about me