A shell script for fetching pull request review comments based on current git context

pr_comment.sh

#!/bin/bash

# Script to fetch Pull Request review comments based on the current Git context.

set -euo pipefail # Exit on error, unset variable, or pipe failure

# --- Configuration ---
# Prefer 'origin' remote, fall back to 'upstream'
readonly PRIMARY_REMOTE="origin"
readonly FALLBACK_REMOTE="upstream"

# --- Helper Functions ---

# Print error message to stderr and exit
error_exit() {
  echo "Error: $1" >&2
  exit 1
}

# Check if a command exists in PATH
check_command() {
  local cmd="$1"
  if ! command -v "$cmd" &> /dev/null; then
    error_exit "Required command '$cmd' is not installed or not found in PATH."
  fi
}

# Get the remote URL, preferring primary, falling back to secondary
get_git_remote_url() {
  local url
  url=$(git config --get remote."$PRIMARY_REMOTE".url || true) # Allow command to fail without exiting script
  if [[ -z "$url" ]]; then
    echo "Warning: Remote '$PRIMARY_REMOTE' not found, trying '$FALLBACK_REMOTE'..." >&2
    url=$(git config --get remote."$FALLBACK_REMOTE".url || true)
  fi

  if [[ -z "$url" ]]; then
    error_exit "Could not determine remote URL (checked '$PRIMARY_REMOTE' and '$FALLBACK_REMOTE')."
  fi
  echo "$url"
}

# Parse GitHub organization and repository name from a URL
parse_org_repo() {
  local url="$1"
  local org_repo
  # Handles https://, git@, and removes .git suffix
  org_repo=$(echo "$url" | sed -E 's/^(https?:\/\/|git@)[^:\/]+[:\/]//; s/\.git$//')
  if [[ ! "$org_repo" == */* ]]; then
    error_exit "Could not parse organization/repository from remote URL: $url"
  fi
  echo "$org_repo" # Returns format "org/repo"
}

# Get the current Git branch name
get_current_branch() {
  local branch
  branch=$(git branch --show-current)
  if [[ -z "$branch" ]]; then
    error_exit "Could not determine current branch."
  fi
  echo "$branch"
}

# Find the PR number associated with a branch and repo
# Tries open PRs first, then the most recent closed/merged PR.
find_pr_number() {
  local branch="$1"
  local org_repo="$2"
  local pr_number

  echo "--> Searching for open PR associated with branch '$branch'..." >&2
  pr_number=$(gh pr list --head "$branch" --repo "$org_repo" --state open --json number --limit 1 --jq '.[0].number // empty' || true)

  if [[ -z "$pr_number" ]]; then
    echo "--> No open PR found. Searching for most recent closed/merged PR..." >&2
    # Use --state all and filter with --search for merged/closed states and the specific head branch
    # Also sort by updated date descending to get the most recent one.
    pr_number=$(gh pr list --repo "$org_repo" --state all --search "head:\"$branch\" is:merged,closed sort:updated-desc" --json number --limit 1 --jq '.[0].number // empty' || true)

    if [[ -z "$pr_number" ]]; then
      error_exit "No open, closed, or merged Pull Request found for branch '$branch' in $org_repo."
    else
      echo "--> Found most recent closed/merged PR: #$pr_number" >&2
    fi
  else
      echo "--> Found open PR Number: #$pr_number" >&2
  fi

  echo "$pr_number"
}

# Fetch comments for a given PR number
fetch_pr_comments() {
    local org_repo="$1"
    local pr_number="$2"
    local api_path="/repos/$org_repo/pulls/$pr_number/comments"
    local output

    echo "--> Fetching comments for PR #$pr_number..." >&2
    # Try with cache first
    output=$(gh api "$api_path" --cache 1h -q '[.[] | {reviewer: .user.login, comment: .body, file: .path, line: (.original_line // .line)}]' 2>/dev/null || true)

    # Validate output or retry without cache
    if [[ -z "$output" ]] || (! echo "$output" | jq empty > /dev/null 2>&1 ); then
        echo "--> Retrying comment fetch without cache..." >&2
        output=$(gh api "$api_path" --cache 0 -q '[.[] | {reviewer: .user.login, comment: .body, file: .path, line: (.original_line // .line)}]' 2>/dev/null || true)

        # Final validation after retry
        if [[ -z "$output" ]] || (! echo "$output" | jq empty > /dev/null 2>&1 ); then
            error_exit "Failed to fetch or process comments from GitHub API for PR #$pr_number, even after retry."
        fi
    fi
    echo "$output"
}

# --- Main Script Logic ---

# --- Argument Parsing ---
pr_number_arg=""
if [[ $# -gt 0 ]] && [[ "$1" =~ ^[0-9]+$ ]]; then
    pr_number_arg="$1"
    echo "--> Using provided PR number: #$pr_number_arg" >&2
fi

# --- Initial Checks ---
check_command "git"
check_command "gh"
check_command "jq"
if ! git rev-parse --is-inside-work-tree &> /dev/null; then
  error_exit "Not inside a git repository."
fi

# Detect Context
remote_url=$(get_git_remote_url)
org_repo=$(parse_org_repo "$remote_url")
echo "--> Detected Repository: $org_repo" >&2

# --- Determine PR Number ---
if [[ -n "$pr_number_arg" ]]; then
    pr_number="$pr_number_arg"
    # Optional: Add a check here to verify the PR exists in the repo?
    # gh pr view "$pr_number" --repo "$org_repo" > /dev/null || error_exit "PR #$pr_number not found in $org_repo."
else
    # Only detect branch and find PR if number wasn't provided
    current_branch=$(get_current_branch)
    echo "--> Detected Branch: $current_branch" >&2
    pr_number=$(find_pr_number "$current_branch" "$org_repo")
fi

# Fetch and Output Comments
comments_json=$(fetch_pr_comments "$org_repo" "$pr_number")

if [[ "$comments_json" == "[]" ]]; then
    echo "--> No review comments found for PR #$pr_number." >&2
else
    # Format the output for better readability (e.g., for LLM input)
    echo "Review comments for PR #$pr_number in $org_repo:"
    echo "---"
    echo "$comments_json" | jq -c '.[]' | while IFS= read -r comment_obj; do
        file=$(echo "$comment_obj" | jq -r '.file')
        line=$(echo "$comment_obj" | jq -r '.line')
        reviewer=$(echo "$comment_obj" | jq -r '.reviewer')
        comment_body=$(echo "$comment_obj" | jq -r '.comment')

        echo "File: $file"
        echo "Line: $line"
        echo "Reviewer: $reviewer"
        echo "Comment:"
        # Indent comment body slightly for clarity
        # Use parameter expansion or printf instead of sed for simple substitution
        while IFS= read -r line; do
          printf '  %s\n' "$line"
        done <<< "$comment_body"
        echo "---"
    done
fi