tessl/npm-google-closure-compiler

Node.js wrapper and build tool plugins for Google's Closure Compiler that compiles, optimizes, and compresses JavaScript code

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Overview

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Command Line Interface

Name: tessl/npm-google-closure-compiler
Author: tessl

The google-closure-compiler package provides a command-line interface that wraps the Closure Compiler with additional Node.js-specific features like platform selection and argument processing.

Capabilities

CLI Executable

The package installs a google-closure-compiler executable that can be used directly from the command line.

# Basic usage
google-closure-compiler --js=input.js --js_output_file=output.js

# With compilation level
google-closure-compiler --js=src/**/*.js --compilation_level=ADVANCED --js_output_file=dist/app.min.js

# Platform selection (CLI-specific flag)
google-closure-compiler --platform=native --js=app.js --js_output_file=app.min.js
google-closure-compiler --platform=java --js=app.js --js_output_file=app.min.js
google-closure-compiler --platform=native,java --js=app.js --js_output_file=app.min.js

Platform Selection

The CLI supports a special --platform flag for choosing the compiler implementation.

# Platform options:
--platform=native         # Use native binary (fastest, platform-specific)
--platform=java           # Use Java JAR (requires Java runtime)
--platform=native,java    # Try native first, fallback to Java
--platform=java,native    # Try Java first, fallback to native

Usage Examples:

# Force native binary usage
google-closure-compiler --platform=native --js=app.js --js_output_file=app.min.js

# Force Java usage (useful for CI/CD environments)
google-closure-compiler --platform=java --js=app.js --js_output_file=app.min.js

# Use with multiple input files
google-closure-compiler \
  --platform=native \
  --js=src/utils.js \
  --js=src/main.js \
  --compilation_level=SIMPLE \
  --js_output_file=dist/bundle.js

# Module compilation with CommonJS support
google-closure-compiler \
  --js=src/**/*.js \
  --module_resolution=NODE \
  --process_common_js_modules \
  --entry_point=src/main.js \
  --compilation_level=ADVANCED \
  --js_output_file=dist/bundle.js

# Type checking only (no output generation)
google-closure-compiler \
  --js=src/**/*.js \
  --compilation_level=ADVANCED \
  --checks_only \
  --warning_level=VERBOSE

Argument Processing

The CLI automatically processes and normalizes command-line arguments.

# Boolean arguments - all equivalent:
google-closure-compiler --debug=true --js=app.js
google-closure-compiler --debug true --js=app.js  
google-closure-compiler --debug --js=app.js

# Array arguments - multiple values:
google-closure-compiler --js=file1.js --js=file2.js --js=file3.js
google-closure-compiler file1.js file2.js file3.js  # Default arguments become --js

# String escaping for complex paths:
google-closure-compiler --js="src/**/*.js" --js_output_file="dist/app.min.js"

Standard Closure Compiler Flags

All standard Google Closure Compiler flags are supported. Common examples:

# Compilation levels
--compilation_level=WHITESPACE_ONLY    # Remove whitespace only
--compilation_level=SIMPLE             # Basic optimizations
--compilation_level=ADVANCED           # Advanced optimizations with type checking

# Language options
--language_in=ECMASCRIPT_2018
--language_out=ECMASCRIPT5

# Source maps
--create_source_map=output.js.map
--source_map_format=V3

# Module resolution
--module_resolution=NODE
--process_common_js_modules

# Output formatting
--formatting=PRETTY_PRINT
--output_wrapper="(function(){%output%})()"

# Debugging and warnings
--debug
--warning_level=VERBOSE
--jscomp_warning=checkTypes

Usage Examples:

# Advanced compilation with source maps
google-closure-compiler \
  --js=src/**/*.js \
  --compilation_level=ADVANCED \
  --js_output_file=dist/app.min.js \
  --create_source_map=dist/app.min.js.map \
  --source_map_format=V3 \
  --warning_level=VERBOSE

# Simple optimization for legacy browsers
google-closure-compiler \
  --js=modern-app.js \
  --compilation_level=SIMPLE \
  --language_out=ECMASCRIPT5 \
  --js_output_file=legacy-app.js

# Node.js module compilation
google-closure-compiler \
  --js=src/**/*.js \
  --compilation_level=ADVANCED \
  --module_resolution=NODE \
  --process_common_js_modules \
  --js_output_file=dist/bundle.js

Exit Codes and Error Handling

The CLI returns standard exit codes for script integration.

# Exit codes:
# 0 - Success
# 1 - Compilation error
# 1 - Process spawn error (Java not found, etc.)

Usage in Scripts:

#!/bin/bash

# Check compilation success
if google-closure-compiler --js=app.js --js_output_file=app.min.js; then
  echo "Compilation successful"
else
  echo "Compilation failed with exit code $?"
  exit 1
fi

# With error capture
ERROR_OUTPUT=$(google-closure-compiler --js=app.js --js_output_file=app.min.js 2>&1)
if [ $? -ne 0 ]; then
  echo "Compilation failed: $ERROR_OUTPUT"
fi

NPX Usage

The package can be used with npx without installation:

# One-time usage with npx
npx google-closure-compiler --js=app.js --js_output_file=app.min.js

# Platform selection with npx
npx google-closure-compiler --platform=native --js=app.js --js_output_file=app.min.js

Implementation Details

The CLI performs several preprocessing steps:

Platform Detection: Determines available compiler implementations
Argument Parsing: Uses minimist to parse command-line arguments
Boolean Conversion: Converts string 'true'/'false' to actual booleans
Default Arguments: Treats non-flagged arguments as --js inputs
Platform Flag Removal: Strips --platform before passing to compiler

// Internal CLI processing (for reference):
interface CLIProcessing {
  // Parse arguments with minimist
  parseArgs(argv: string[]): Object;
  
  // Convert platform preference to supported platform
  getFirstSupportedPlatform(platforms: string[]): 'native' | 'java';
  
  // Move default arguments to --js flag
  processDefaultArguments(args: Object): Object;
  
  // Convert string booleans to actual booleans
  normalizeBooleans(args: Object): Object;
}