Ninja

Warnings

• breaking Versions of the `ninja` Python package after 1.13 no longer support Python 3.7. Similarly, versions after 1.11.1.1 dropped support for Python 2-3.6.
  Fix: Upgrade your Python environment to 3.8 or newer if using recent `ninja` versions.
• breaking The `pipes` module, which `ninja` relies on, was deprecated and removed in Python 3.13. This causes build failures when `ninja` is used with Python 3.13 or newer.
  Fix: Downgrade your Python environment to 3.12 or earlier when using the `ninja` Python package. Alternatively, use a virtual environment with an older Python version.
• gotcha Ninja is designed as a low-level build system. Its `.ninja` input files are intended to be generated by a higher-level build system (like CMake or Meson), not written or maintained by hand for complex projects. Attempting to manage complex build logic directly within `.ninja` files is an anti-pattern.
  Fix: For complex projects, use a build system generator (e.g., CMake, Meson) to produce the `.ninja` files. Use `ninja_syntax` for simpler, programmatic generation if direct Python control is desired.
• gotcha Building the `ninja` Python package from source using `--no-binary=ninja` can fail if CMake is not already installed on the system, as `ninja`'s build process sometimes requires CMake.
  Fix: Ensure CMake is installed and in your PATH before attempting to install `ninja` with `--no-binary` flags, or prefer installing pre-built binary wheels.
• gotcha Incorrectly generated dependency files (`dep-files`) by certain compilers can lead to `ninja` always triggering full re-builds even when no changes have occurred.
  Fix: Verify the `dep-file` output format of your compiler. If necessary, wrap your compiler with a script to correct the `dep-file` format, or configure `ninja` to use alternative dependency scanning if available.

Install

• pip install ninja Install latest version

Imports

• ninja_syntax

  from ninja_syntax import Writer

  Used to programmatically generate .ninja build files. The module is provided by the `ninja` package.

Quickstart

This quickstart demonstrates how to use `ninja_syntax` to programmatically generate a `build.ninja` file for a simple C project, and then execute the `ninja` command to build it. Ensure you have a C compiler (like `gcc`) installed and that `ninja` (the executable) is in your system's PATH.

import subprocess
from ninja_syntax import Writer
import os

# Create a simple build.ninja file
with open('build.ninja', 'w') as f:
    writer = Writer(f)
    writer.variable('cflags', '-Wall -Wextra')
    writer.rule('cc', 'gcc $cflags -c $in -o $out')
    writer.rule('link', 'gcc $in -o $out')
    writer.build('hello.o', 'cc', 'hello.c')
    writer.build('hello', 'link', 'hello.o')
    writer.default('hello')

# Create a dummy source file
with open('hello.c', 'w') as f:
    f.write("""
#include <stdio.h>

int main() {
    printf("Hello, Ninja!\n");
    return 0;
}
""")

print("Generated build.ninja and hello.c. Running ninja...")

try:
    # Run ninja
    result = subprocess.run(['ninja'], capture_output=True, text=True, check=True)
    print("Ninja build successful!")
    print("\nStdout:\n", result.stdout)
    if result.stderr:
        print("\nStderr:\n", result.stderr)

    # Optionally, run the built executable
    print("\nRunning built executable...")
    exec_result = subprocess.run(['./hello'], capture_output=True, text=True, check=True)
    print("Executable output:\n", exec_result.stdout)

except subprocess.CalledProcessError as e:
    print(f"Ninja build failed with error: {e}")
    print("\nStdout:\n", e.stdout)
    print("\nStderr:\n", e.stderr)
except FileNotFoundError:
    print("Error: 'ninja' command not found. Please ensure Ninja is installed and in your PATH.")

# Clean up generated files (optional)
# os.remove('build.ninja')
# os.remove('hello.c')
# if os.path.exists('hello.o'):
#     os.remove('hello.o')
# if os.path.exists('hello'):
#     os.remove('hello')