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wheels env merge

Overview

The wheels env merge command allows you to merge multiple environment configuration files (.env files) into a single consolidated file. This is particularly useful when working with different environments (development, staging, production) or when you have base configurations that need to be combined with environment-specific overrides.

Command Syntax

wheels env merge <source1> <source2> [source3...] [options]

Parameters

Required Parameters

  • source1 - First source .env file to merge

  • source2 - Second source .env file to merge

Optional Parameters

  • source3, source4, ... - Additional source .env files to merge (unlimited)

  • --output - Output file name (default: .env.merge)

  • --dryRun - Show what would be merged without actually writing the file

Basic Usage Examples

Simple Two-File Merge

wheels env merge .env.defaults .env.local

This merges .env.defaults and .env.local into .env.merge

Custom Output File

wheels env merge .env.defaults .env.local --output=.env

This merges the files and saves the result as .env

Production Environment Merge

wheels env merge source1=.env source2=.env.production --output=.env.merged

Combines base configuration with production-specific settings

Multiple File Merge

wheels env merge source1=base.env source2=common.env source3=dev.env source4=local.env --output=.env.development

Merges multiple files in the specified order (unlimited number of source files supported)

Dry Run (Preview)

wheels env merge base.env override.env --dryRun

Shows what the merged result would look like without creating a file

How It Works

File Processing Order

Files are processed in the order they are specified on the command line. Later files take precedence over earlier ones when there are conflicting variable names.

Supported File Formats

  • Properties format (standard .env format):

    DATABASE_HOST=localhost
DATABASE_PORT=5432
API_KEY=your-secret-key

  • JSON format:

    {
  "DATABASE_HOST": "localhost",
  "DATABASE_PORT": "5432",
  "API_KEY": "your-secret-key"
}

File Parsing Details

  • Empty lines and comments (lines starting with #) are skipped in properties files

  • Values can contain = signs (everything after the first = is considered the value)

  • Leading and trailing whitespace is trimmed from keys and values

  • The command automatically detects whether a file is JSON or properties format

Conflict Resolution

When the same variable exists in multiple files:

  • The value from the last processed file wins

  • Conflicts are tracked and reported with details showing:

    • The variable name

    • The original value and source file

    • The new value and source file

  • You'll see a summary showing which values were overridden

Output Features

Organized Structure

The merged output file is automatically organized:

  • Variables are grouped by prefix (e.g., DATABASE_*, API_*)

  • Groups are sorted alphabetically

  • Variables within groups are sorted alphabetically

  • Includes generated header comments with:

    • Generation timestamp

    • Source information

    • Section headers for each variable group

Security Features

When using --dryRun or viewing output, sensitive values are automatically masked:

  • Variables containing password, secret, key, or token (case-insensitive) show as ***MASKED***

  • The actual values are still written to the output file (only display is masked)

  • Each variable shows its source file for traceability

Common Use Cases

Development Workflow

# Start with base configuration
wheels env merge source1=.env.base source2=.env.development --output=.env

# Add local overrides
wheels env merge source1=.env source2=.env.local --output=.env

Multi-Environment Setup

# Merge base, environment, and local configs
wheels env merge source1=.env.base source2=.env.staging source3=.env.local --output=.env

Deployment Preparation

# Create production configuration
wheels env merge source1=.env.base source2=.env.production --output=.env.prod

# Preview staging configuration
wheels env merge source1=.env.base source2=.env.staging --dryRun

Configuration Validation

# Check what the final configuration looks like
wheels env merge source1=.env.defaults source2=.env.current --dryRun

Sample Output

Command Execution

Merging environment files:
  1. .env.defaults
  2. .env.local
  3. .env.override

Merged 3 files into .env.merge
  Total variables: 15

Conflicts resolved (later files take precedence):
  DATABASE_HOST: 'db.example.com' (.env.defaults) → 'localhost' (.env.local)
  DEBUG_MODE: 'false' (.env.defaults) → 'true' (.env.override)

Dry Run Output

Merged result (DRY RUN):

DATABASE Variables:
  DATABASE_HOST = localhost (from .env.local)
  DATABASE_NAME = myapp (from .env.defaults)
  DATABASE_PASSWORD = ***MASKED*** (from .env.local)
  DATABASE_PORT = 5432 (from .env.defaults)

API Variables:
  API_BASE_URL = https://api.example.com (from .env.defaults)
  API_KEY = ***MASKED*** (from .env.local)
  API_TOKEN = ***MASKED*** (from .env.override)

Other Variables:
  APP_NAME = MyApplication (from .env.defaults)
  DEBUG_MODE = true (from .env.override)

Generated File Format

# Merged Environment Configuration
# Generated by wheels env merge command
# Date: 2024-12-15 14:30:45

# API Configuration
API_BASE_URL=https://api.example.com
API_KEY=actual-key-value
API_TOKEN=actual-token-value

# DATABASE Configuration
DATABASE_HOST=localhost
DATABASE_NAME=myapp
DATABASE_PASSWORD=actual-password
DATABASE_PORT=5432

# Other Configuration
APP_NAME=MyApplication
DEBUG_MODE=true

Error Handling

The command will stop and show an error if:

  • Source files don't exist

  • Less than two source files are provided

  • Output file cannot be written (permissions, disk space, etc.)

  • File read operations fail

Important Notes

  1. Default output filename is .env.merge (not .env.merged)

  2. Multiple files supported - You can merge any number of files (not just 2 or 3)

  3. Option format - Use double dashes for options: --output, --dryRun

  4. Value preservation - Values containing = signs are properly preserved

  5. Comment handling - Comments in source files are not preserved in the merged output

Best Practices

  1. Use descriptive file names that indicate their purpose (.env.base, .env.production, .env.local)

  2. Order files by precedence - place base/default files first, overrides last

  3. Use dry-run first to preview results before committing to a merge

  4. Keep sensitive data in local files that aren't committed to version control

  5. Document your merge strategy in your project's README

  6. Backup important configurations before merging

  7. Review conflicts - Pay attention to the conflicts report to ensure expected overrides

Tips

  • The merged file includes helpful comments showing when it was generated

  • Variables are automatically organized by prefix for better readability

  • Use the --dryRun option to understand what changes will be made

  • The command validates all source files exist before starting the merge process

  • You can merge as many files as needed in a single command

  • The source file information is preserved during dry runs for debugging

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