bloaty

#!/usr/bin/env python3
# Small utility on top of cargo bloat.

import json
import subprocess
import sys
import os

command = sys.argv[1]

BASELINE_FILE = "bloaty.log"

def run_cargo_bloat():
    completed = subprocess.run("cargo bloat --release --message-format json -n 0", shell=True, check=True, capture_output=True)
    if completed.returncode != 0:
        sys.exit(completed.stderr)
    baseline = json.loads(completed.stdout)
    data = {}
    for f in baseline["functions"]:
        name = f["name"]
        size = f["size"]
        if name in baseline:
            data[name] += size
        else:
            data[name] = size
    return {"functions":data}

def read_baseline():
    if os.path.isfile(BASELINE_FILE):
        with open(BASELINE_FILE, "r") as infile:
            return json.load(infile)
    else:
        sys.exit("No baseline - run: bloaty save <description>")

if command == "save":
    data = run_cargo_bloat()
    data["bloatydescription"] = ' '.join(sys.argv[2:])
    with open(BASELINE_FILE, "w") as outfile:
        json_object = json.dumps(data, indent=4)
        outfile.write(json_object)
elif command == "show":
    baseline = read_baseline()
    print(baseline["bloatydescription"])
elif command == "diff":
    baseline = read_baseline()
    print("# Comparing with " + baseline["bloatydescription"])
    current = run_cargo_bloat()
    total_diff_bytes = 0
    for (name, current_size) in current["functions"].items():
        if name in baseline["functions"]:
            old_size = baseline["functions"][name]
            diff_bytes = current_size - old_size
            if diff_bytes != 0:
                total_diff_bytes += diff_bytes
                print(f"{name}: {diff_bytes} - old={old_size}, new={current_size}")
        else:
            print(f"New function: {name}, size={current_size}")
    print(f"Total: {total_diff_bytes}")
else:
    sys.exit(f"Unknown command: {command} - use save/show/diff")