format-incremental

#!/usr/bin/env bash
# Copyright 2025 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

################################################################################
# Formats Python files that have been modified.
#
# Usage:
#     check/format-incremental [BASE_REVISION] [--apply] [--all]
#
# By default, the script analyzes Python files that have changed relative to the
# base revision and determines whether they need to be formatted. If any changes
# are needed, it prints the diff and exits with code 1, otherwise it exits with
# code 0.
#
# With '--apply', reformats the files instead of printing the diff and exits
# with code 0.
#
# With '--all', analyzes all files, instead of only changed files.
#
# You can specify a base git revision to compare against (i.e. to use when
# determining whether or not a file is considered to have "changed"). For
# example, you can compare against 'origin/main' or 'HEAD~1'.
#
# If you don't specify a base revision, the following defaults will be tried, in
# order, until one exists:
#
#     1. upstream/main
#     2. origin/main
#     3. main
#
# If none exists, the script fails.
#
# This script is based on the Cirq script of the same name:
# https://github.com/quantumlib/Cirq/blob/main/check/format-incremental
################################################################################

# Get the working directory to the repo root.
thisdir=$(dirname "${BASH_SOURCE[0]:?}") || exit $?
repo_dir=$(git -C "${thisdir}" rev-parse --show-toplevel) || exit $?
cd "${repo_dir}" || exit $?

# Parse arguments.
only_print=1
only_changed=1
rev=""
for arg in "$@"; do
    if [[ "${arg}" == "--apply" ]]; then
        only_print=0
    elif [[ "${arg}" == "--all" ]]; then
        only_changed=0
    elif [ -z "${rev}" ]; then
        if ! git rev-parse --verify --quiet --no-revs "${arg}^{commit}"; then
            echo -e "\033[31mNo revision '${arg}'.\033[0m" >&2
            exit 1
        fi
        rev="${arg}"
    else
        echo -e "\033[31mToo many arguments." \
             "Expected [revision] [--apply] [--all].\033[0m" >&2
        exit 1
    fi
done

declare -a format_files
if (( only_changed == 1 )); then
    # Figure out which branch to compare against.
    if [ -z "${rev}" ]; then
        if [ "$(git cat-file -t upstream/main 2> /dev/null)" == "commit" ]; then
            rev=upstream/main
        elif [ "$(git cat-file -t origin/main 2> /dev/null)" == "commit" ]; then
            rev=origin/main
        elif [ "$(git cat-file -t main 2> /dev/null)" == "commit" ]; then
            rev=main
        else
            echo -e "\033[31mNo default revision found to compare against."\
                 "Argument #1 must be what to diff against" \
                 "(e.g. 'origin/main' or 'HEAD~1').\033[0m" >&2
            exit 1
        fi
    fi
    base=$(git merge-base "${rev}" HEAD)
    if [ "$(git rev-parse "${rev}")" == "${base}" ]; then
        echo -e "Comparing against revision '${rev}'." >&2
    else
        echo -e "Comparing against revision '${rev}' (merge base ${base})." >&2
        rev="${base}"
    fi

    # Get the modified, added, and moved files.
    IFS=$'\n' read -r -d '' -a format_files < \
        <(git diff --name-only --diff-filter=MAR "${rev}" -- '*.py') || true
else
    echo -e "Formatting all Python files." >&2
    IFS=$'\n' read -r -d '' -a format_files < \
        <(git ls-files '*.py')
fi

if (( ${#format_files[@]} == 0 )); then
    echo -e "\033[32mNo files to format.\033[0m"
    exit 0
fi

# Color the output if it goes to a terminal or GitHub Actions log.
arg_color=()
if [[ -t 1 || "${CI}" == true ]]; then
    # Check if ruff supports --color (it might be missing in older/some versions).
    if ruff --help 2>&1 | grep -q -- '--color'; then
        arg_color=("--color" "always")
    fi
fi

# Run ruff for import sorting.
# We do this first so that if it changes files, the formatting step will pick them up.
echo "Running ruff check (isort)..."
check_args=("check" "--select" "I" "${arg_color[@]}")
if (( only_print == 0 )); then
    check_args+=("--fix")
else
      # In check mode, we want to see diffs if possible, but ruff check usually just prints violations.
      # To match previous behavior of "checking" without modifying, we don't add --fix.
      # If we want diffs for imports, --diff can be used.
      check_args+=("--diff")
fi

RUFF_CHECK_STATUS=0
if (( "${#format_files[@]}" )); then
    # We pass all files to ruff; it handles excluding those that shouldn't be touched if configured,
    # but here we are passing a specific list of files.
    ruff "${check_args[@]}" "${format_files[@]}"
    RUFF_CHECK_STATUS=$?
fi

echo "Running ruff format..."
format_args=("format" "${arg_color[@]}")
if (( only_print == 1 )); then
    format_args+=("--check" "--diff")
fi

RUFF_FORMAT_STATUS=0
if (( "${#format_files[@]}" )); then
    ruff "${format_args[@]}" "${format_files[@]}"
    RUFF_FORMAT_STATUS=$?
fi

if (( RUFF_CHECK_STATUS || RUFF_FORMAT_STATUS )); then
  exit 1
fi
exit 0