#!/bin/bash
#
# Intended for use in CI: check git commits, barf if no tests added.
#
ME=$(basename $0)

# Github label which allows overriding this check
OVERRIDE_LABEL="No New Tests"

# PR head commit; defaults to HEAD when not running in CI.
head=${PR_HEAD:-HEAD}
# Base of this PR.
base=$(git merge-base ${DEST_BRANCH:-main} $head)

# This gives us a list of files touched in all commits, e.g.
#    A    foo.c
#    M    bar.c
# We look for Added or Modified (not Deleted!) files under 'test'.
# --no-renames ensures that renamed tests (#9420) show up as 'A'dded.
if git diff --name-status --no-renames $base $head | grep -E -q '^[AM]\s+(test/|.*_test\.go)'; then
    exit 0
fi

# Nothing changed under test subdirectory.
#
# This is OK if no source code files were changed.
# Also we allow vendor updated without tests so exclude the vendor files
# and also the version files so release PRs do not need tests.
filtered_changes=$(git diff --name-only $base $head |
    grep -E -v '^(test/tools/)?vendor/' |
    grep -E -v '^version/' |
    grep -E -x '.*\.(go|c|h)')
if [[ -z "$filtered_changes" ]]; then
    exit 0
fi

# This PR touches non-test files but adds no tests. Only allow it if the
# '$OVERRIDE_LABEL' github label is set.
if [[ -n "$PR_NUMBER" ]]; then
    for var in GITHUB_TOKEN GITHUB_REPOSITORY; do
        if [[ -z "${!var}" ]]; then
            echo "$ME: cannot query github: \$$var is undefined" >&2
            return 1
        fi
    done

    labels=$(curl --fail -s \
        -H "Authorization: bearer $GITHUB_TOKEN" \
        -H "Accept: application/vnd.github+json" \
        "https://api.github.com/repos/${GITHUB_REPOSITORY}/pulls/$PR_NUMBER" |
        jq -r '.labels[].name')

    if grep -F -x -q "$OVERRIDE_LABEL" <<< "$labels"; then
        echo "$ME: \"$OVERRIDE_LABEL\" label found, ignoring test requirements"
        exit 0
    fi
fi

# This PR touches non-test files but adds no tests, and
# the '$OVERRIDE_LABEL' is not set. Fail loudly.
cat << EOF
$ME: PR does not include changes in the 'tests' directory

Please write a regression test for what you're fixing. Even if it
seems trivial or obvious, try to add a test that will prevent
regressions.

If your change is minor, feel free to piggyback on already-written
tests, possibly just adding a small step to a similar existing test.
Every second counts in CI.

If your commit really, truly does not need tests, you can proceed
by asking a repo maintainer to set the '$OVERRIDE_LABEL' github label.
This will only be done when there's no reasonable alternative.
EOF

exit 1