autoblame.sh

#!/usr/bin/env bash
#
# Given a scalac command line which produces a stack trace, such as
#  <this program> some-scalac crasher.scala
# Tracks down a scala git repository if it can; parses the stack trace
# for files and line numbers; and outputs -3 lines to +3 lines for
# each line in the stack trace, as the file was at the time of the commit.

MaxFrames=10

binDir="$(dirname $(readlink $(which $1)))"
scalaRepo="$(cd "$binDir" && git rev-parse --show-toplevel 2>/dev/null || echo $SCALA_SRC_HOME )"
echo >&2 "Extracted repository root: $scalaRepo"
declare inputLines compilerVersion filesBackThen

run () { echo "% $@" && "$@"; }
rungit () { ( cd "$scalaRepo" && run git --no-pager "$@"; ) }

packageLines () {
  local file="$1"
  local pkg="$2"
  local text="$(egrep '\bpackage\b' "$1")"

  ( IFS=. && for segment in $pkg; do printf "$text\n" | grep -q "$segment" || return 1; done; return 0; )
}

findLine () {
  class="$1"
  method="$2"
  file="$3"
  lineno="$4"

  wcLines () { rungit show $compilerVersion:$1 | wc -l | tr -d ' '; }

  fileChoice="$(
    for f in $(printf "%s\n" "$filesBackThen" | egrep -v ^test/ | egrep "\b${file}$"); do
      [[ $(wcLines "$f") -ge "$lineno" ]] && \
        packageLines "$f" "${class%.*}" && \
        echo "$f"
    done
  )"

  if [[ $fileChoice = *[[:space:]]* ]]; then
    echo "Skipping stack frame $file:$lineno, can't figure out file among $fileChoice"
  else
    last=$(wcLines "$fileChoice")
    start=$(( lineno - 3 ))
    end=$(( lineno + 3 ))
    [[ $end -gt $last ]] && end=$last
    rungit blame --abbrev=5 -C20 -M10 --show-name --show-number --date=short -L $start,$end "$fileChoice" "$compilerVersion" || exit 1
    echo ""
  fi
}

finder () {
  local -i frames=0
  while read line; do
    if [[ $line =~ ^[[:space:]]*at([^\(]*)\(([^\)]*)\) ]]; then
      classAndMethod="${BASH_REMATCH[1]}"
      fileAndLine="${BASH_REMATCH[2]}"
      method="${classAndMethod##*.}"
      class="${classAndMethod%.*}"
      file="${fileAndLine%:*}"
      lineno="${fileAndLine##*:}"
      findLine "$class" "$method" "$file" "$lineno"
      (( frames += 1 ))
      [[ $frames -gt $MaxFrames ]] && exit 0;
    fi
  done
}

extractCompilerVersion () {
  # Scala compiler version 2.11.0-20130606-140622-209ee3cbc5 -- Copyright 2002-2013, LAMP/EPFL
  local compilerVersion="$("$1" -version 2>&1 | words | egrep '^[0-9]' | head -n1)"
  # if it's something like "2.11.0-20130608-041104-feb660ccd7" it's still
  # very long, and if it's not, it needs a "v" in front to be a git version.
  # the eternal struggle continues.
  if [[ ${#compilerVersion} -gt 15 ]]; then
    compilerVersion="${compilerVersion##*-}"
  else
    compilerVersion="v${compilerVersion}"
  fi

  echo "$compilerVersion"
}

compilerVersion="$(extractCompilerVersion "$1")"
echo >&2 "Extracted scala compiler version: $compilerVersion"
rungit log -n1 "$compilerVersion"

filesBackThen="$(rungit ls-tree --full-tree -r "$compilerVersion" -- . | awk '{ print $NF }')"
inputLines="$("$@" 2>&1)"

printf "$inputLines" | finder