Piping output of shell command to grep causes "grep: write error" - crystal-lang

Question

I wrote a tool in Crystal that takes some command line parameters, and turns those into, basically, "find stuff | xargs grep" where xargs is instructed to use multiple processes. This is run via Process.run, and output and error are redirected into a custom IO object which filters what comes out of grep a bit, writing everything that isn't filtered into STDOUT.
When I run this normally, it mostly seems to run fine. There do seem to be some instances of output getting cut off before the search completes though, so I'm not sure I can fully trust the results. When I pipe the output from this command into grep, however, it always cuts off the search early and says "grep: write error". I have no idea why this is happening, and would love some help. Eventually I'll likely rewrite this to do everything in pure Crystal, but for now this is a quick solution to search the codebase I'm working on.
Here is the code that is getting run:
class FindFilterIO
include IO
##generic_filter = [".diff", ".iml", "/target/"]
##web_filter = [".css", ".js", ".jsp", ".ftl"]
def initialize(#web_search : Bool = false)
end
def read(slice : Bytes)
raise "FindFilterIO does not support reading!"
end
def write(slice : Bytes)
str = String.new slice
if ##generic_filter.any? { |e| str.includes? e }
return
end
if #web_search
if !##web_filter.any? { |e| str.includes? e }
return
end
end
STDOUT.write(slice)
end
end
cmd = "find . -not \\( -path ./.svn -prune \\) " \
"-not \\( -path ./.idea -prune \\) " \
"-type f -print0 " \
"| xargs -0 -P 1 -n 100 grep -E -n --color=always "
cmd += if #html_id
"'id=['\"'\"'\"]#{#search_text}['\"'\"'\"]|\##{#search_text}'"
elsif #html_class
"'class=['\"'\"'\"]#{#search_text}['\"'\"'\"]|\\.#{#search_text}'"
else
"'#{#search_text}'"
end
io = FindFilterIO.new web_search: (#html_id || #html_class)
Process.run(cmd, output: io, error: io, shell: true, chdir: File.join(#env.home_dir, #env.branch, "repodir"))

Answer 1

This seems to have been fixed now that the issue at https://github.com/crystal-lang/crystal/issues/2065 has been closed. Will need to do some more testing to make sure it's totally fixed, but using my older code seems to be working fine now.