preview code coverage changes for github.com/google/go-github

cov-preview

#!/bin/sh
#/ cov-preview [base]
#/
#/ Compare coverage of the worktree against the base. Exits non-zero When the
#/ coverage of modified code is less than 100% or the net coverage decreases.
#/ This is intended to mimic the codecov rules on github.com/google/go-github.
#/ Changes that remove covered code may error here but not on codecov.
#/
#/ Default base is HEAD (meaning  you are comparing uncommitted changes against
#/ the last commit).

set -e

GO_PATH_COVER_TAG="v0.2.0"

if [ "$#" -gt 1 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
  grep '^#/' <"$0" | cut -c4-
  exit 1
fi

BASE="${1:-HEAD}"

COV_DIR="$(mktemp -d)"
WORKTREE_DIR="$(mktemp -d)"
git worktree add -q --detach "$WORKTREE_DIR" "$BASE"
trap 'git worktree remove -f "$WORKTREE_DIR"; rm -rf "$WORKTREE_DIR" "$COV_DIR"' EXIT

git diff -U0 --no-color "$BASE" > "$COV_DIR"/patch.diff

echo "Running tests on the current worktree".
go test -coverprofile="$COV_DIR"/head.out ./...

(
  cd "$WORKTREE_DIR"
  echo "Running tests on $BASE"
  go test -coverprofile="$COV_DIR"/base.out ./...
)

stats="$(
  go run github.com/seriousben/go-patch-cover/cmd/go-patch-cover@"$GO_PATH_COVER_TAG" \
    -o json \
    "$COV_DIR"/head.out \
    "$COV_DIR"/patch.diff \
    "$COV_DIR"/base.out
)"

jq -r '. | "
Coverage:
  head:
    covered_lines: \(.cover_count)
    total_lines:   \(.num_stmt)
    coverage:      \(.coverage * 10000|round / 10000)%
  base:
    covered_lines: \(.prev_cover_count)
    total_lines:   \(.prev_num_stmt)
    coverage:      \(.prev_coverage * 10000|round / 10000)%
  patch:
    covered_lines: \(.patch_cover_count)
    total_lines:   \(.patch_num_stmt)
    coverage:      \(.patch_coverage * 10000|round / 10000)%
  delta:
    covered_lines: \(.cover_count - .prev_cover_count)
    total_lines:   \(.num_stmt - .prev_num_stmt)
    coverage:      \((.coverage - .prev_coverage) * 10000|round / 10000)%
"' <<<"$stats"

delta="$(jq -r '
  if .coverage < .prev_coverage then
    (.prev_coverage - .coverage) * 10000|round / 10000
  else "" end
' <<<"$stats"
)"

if [ -n "$delta" ]; then
  err=1
  echo "Coverage decreased by ${delta}%" 1>&2
fi

patch_uncovered_lines="$(jq -r '.patch_num_stmt - .patch_cover_count' <<<"$stats")"
if [ "$patch_uncovered_lines" -gt 0 ]; then
  err=1
  echo "Patch contains $patch_uncovered_lines uncovered lines" 1>&2
fi

[ -z "$err" ] || exit 1