angreal-arguments

Angreal Arguments

Add command-line arguments to angreal tasks using the @argument decorator.

Basic Usage

import angreal

@angreal.command(name="greet", about="Greet someone")
@angreal.argument(name="name", long="name", help="Name to greet")
def greet(name="World"):
    print(f"Hello, {name}!")

CLI: angreal greet --name Alice

Decorator Order

Critical: @argument must come AFTER @command:

# Correct
@angreal.command(name="build", about="Build project")
@angreal.argument(name="release", long="release", is_flag=True, takes_value=False)
def build(release=False):
    pass

# Wrong - will fail
@angreal.argument(name="release", is_flag=True)  # Error!
@angreal.command(name="build", about="Build project")
def build(release=False):
    pass

The @argument Decorator

@angreal.argument(
    name,                   # Required: must match function parameter
    short=None,             # Short flag: "v" for -v
    long=None,              # Long flag: "verbose" for --verbose
    help=None,              # Help text for --help
    long_help=None,         # Extended help text (shown with --help)
    required=None,          # Is argument required?
    default_value=None,     # Default (must be string)
    takes_value=True,       # Takes a value? (default True)
    is_flag=False,          # Boolean flag? (default False)
    python_type="str",      # Type: "str", "int", "float"
    multiple_values=None,   # Can be repeated?
    require_equals=None,    # Require --arg=value syntax
    number_of_values=None,  # Exact number of values required
    min_values=None,        # Minimum values when multiple
    max_values=None,        # Maximum values when multiple
)

Parameter Details

Parameter	Type	Description
name	str	Required. Must match function parameter name
short	str	Single character for short flag (e.g., "v" for -v)
long	str	Long flag name (e.g., "verbose" for --verbose)
help	str	Brief help text shown in --help output
long_help	str	Extended help text for detailed documentation
required	bool	Whether the argument must be provided
default_value	str	Default value (always a string, converted by python_type)
takes_value	bool	Whether argument accepts a value (default: True)
is_flag	bool	Boolean flag mode (default: False)
python_type	str	Type conversion: "str", "int", "float"
multiple_values	bool	Allow repeating the argument
require_equals	bool	Require --arg=value instead of --arg value
number_of_values	int	Exact number of values required
min_values	int	Minimum number of values (with multiple_values)
max_values	int	Maximum number of values (with multiple_values)

Argument Types

String Arguments

@angreal.command(name="echo", about="Echo message")
@angreal.argument(name="message", long="message", help="Message to display")
def echo(message="default"):
    print(message)

Integer Arguments

@angreal.command(name="repeat", about="Repeat N times")
@angreal.argument(name="count", long="count", python_type="int", help="Iterations")
def repeat(count=1):
    for i in range(int(count)):
        print(i)

Boolean Flags

Use is_flag=True with takes_value=False:

@angreal.command(name="build", about="Build project")
@angreal.argument(
    name="verbose",
    short="v",
    long="verbose",
    is_flag=True,
    takes_value=False,
    help="Enable verbose output"
)
def build(verbose=False):
    if verbose:
        print("Verbose mode enabled")

CLI: angreal build --verbose or angreal build -v

Required Arguments

@angreal.command(name="deploy", about="Deploy application")
@angreal.argument(
    name="target",
    long="target",
    required=True,
    help="Deployment target (required)"
)
def deploy(target):
    print(f"Deploying to {target}")

Multiple Values

@angreal.command(name="compile", about="Compile files")
@angreal.argument(
    name="file",
    long="file",
    multiple_values=True,
    help="Files to process"
)
def compile(file=None):
    files = file or []
    for f in files:
        print(f"Processing {f}")

CLI: angreal compile --file a.txt --file b.txt

Complete Example

import angreal

@angreal.command(name="build", about="Build the project")
@angreal.argument(
    name="target",
    long="target",
    default_value="debug",
    help="Build target (debug or release)"
)
@angreal.argument(
    name="verbose",
    short="v",
    long="verbose",
    is_flag=True,
    takes_value=False,
    help="Verbose output"
)
@angreal.argument(
    name="jobs",
    short="j",
    long="jobs",
    python_type="int",
    default_value="4",
    help="Parallel jobs"
)
def build(target="debug", verbose=False, jobs=4):
    if verbose:
        print(f"Building {target} with {jobs} jobs")

CLI: angreal build --target release -v -j 8

Common Patterns

Environment Selection

@angreal.argument(
    name="env",
    short="e",
    long="env",
    default_value="development",
    help="Environment: development, staging, production"
)

Dry Run Mode

@angreal.argument(
    name="dry_run",
    short="n",
    long="dry-run",
    is_flag=True,
    takes_value=False,
    help="Show what would be done without making changes"
)

File I/O

@angreal.argument(
    name="input",
    short="i",
    long="input",
    required=True,
    help="Input file path"
)
@angreal.argument(
    name="output",
    short="o",
    long="output",
    help="Output file path (default: stdout)"
)

Function Signature Matching

Parameter names must match argument name values:

@angreal.command(name="cmd", about="Example")
@angreal.argument(name="target", long="target", required=True)
@angreal.argument(name="verbose", long="verbose", is_flag=True, takes_value=False)
def cmd(target, verbose=False):  # Names match!
    pass

Help Text Best Practices

# Good - includes default and constraints
@angreal.argument(
    name="workers",
    long="workers",
    python_type="int",
    default_value="4",
    help="Number of worker processes (1-16, default: 4)"
)

Advanced Parameters

Long Help Text

Use long_help for extended documentation:

@angreal.argument(
    name="format",
    long="format",
    help="Output format",
    long_help="""Output format for the generated report.

Supported formats:
  - json: Machine-readable JSON output
  - csv: Comma-separated values
  - table: Human-readable table (default)

Example: --format=json"""
)

Require Equals Syntax

Force --arg=value instead of --arg value:

@angreal.argument(
    name="config",
    long="config",
    require_equals=True,
    help="Config file (use --config=path)"
)

CLI: angreal cmd --config=settings.toml (not --config settings.toml)

Exact Number of Values

Require exactly N values:

@angreal.argument(
    name="point",
    long="point",
    number_of_values=2,
    help="X Y coordinates"
)
def plot(point):
    x, y = point  # Always receives exactly 2 values

CLI: angreal plot --point 10 20

Value Count Constraints

Limit how many values can be provided:

@angreal.argument(
    name="tags",
    long="tag",
    multiple_values=True,
    min_values=1,
    max_values=5,
    help="Tags (1-5 required)"
)
def tag(tags):
    for t in tags:
        print(f"Tag: {t}")

CLI: angreal tag --tag foo --tag bar --tag baz