Class PythonParameterDefaultValueProvider

java.lang.Object

io.micronaut.python.processing.PythonParameterDefaultValueProvider

All Implemented Interfaces:

Ordered, ParameterDefaultValueProvider

public final class PythonParameterDefaultValueProvider
extends Object
implements ParameterDefaultValueProvider

Supplies the declared default value of a Python parameter, where that default is an immutable literal the generated code can reproduce.

A Python default is evaluated by the interpreter, so in general it is applied by the stub constructor rather than by the caller. A literal is the exception: host: str = "localhost" carries its value into ArgumentDef#defaultValue() at compile time, so it can be passed explicitly and is indistinguishable from letting Python apply it.

Anything else — a mutable literal, a default_factory (an DefaultFactoryDef), a call, a name — yields Optional.empty(), leaving those parameters to the stub's own defaulting. In particular a fresh mutable default must not be materialised here, as Python evaluates a mutable default once at definition time and shares it between calls.

Since:

5.2.0

Author:

graemerocher

Field Summary

Fields inherited from interface Ordered

HIGHEST_PRECEDENCE, LOWEST_PRECEDENCE

Constructor Summary

Constructors

Constructor	Description
PythonParameterDefaultValueProvider()

Method Summary

Modifier and Type	Method	Description
Optional<io.micronaut.sourcegen.model.ExpressionDef>	defaultValueExpression(ParameterElement parameter, @Nullable io.micronaut.sourcegen.model.ExpressionDef target)	Supplies an expression evaluating to the parameter's declared default value.
boolean	supports(ParameterElement parameter)	Whether this provider can supply default values for the given parameter, which is typically a test of the element's language specific implementation type.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface Ordered

getOrder

Constructor Details

PythonParameterDefaultValueProvider

public PythonParameterDefaultValueProvider()

Method Details

supports

public boolean supports(ParameterElement parameter)

Description copied from interface: ParameterDefaultValueProvider

Whether this provider can supply default values for the given parameter, which is typically a test of the element's language specific implementation type.

Specified by:

supports in interface ParameterDefaultValueProvider

Parameters:

parameter - The parameter

Returns:

True if ParameterDefaultValueProvider.defaultValueExpression(ParameterElement, ExpressionDef) should be consulted for this parameter

defaultValueExpression

public Optional<io.micronaut.sourcegen.model.ExpressionDef> defaultValueExpression(ParameterElement parameter,
 @Nullable io.micronaut.sourcegen.model.ExpressionDef target)

Description copied from interface: ParameterDefaultValueProvider

Supplies an expression evaluating to the parameter's declared default value.

The returned expression must be assignable to the erasure of ParameterElement.getType() and must be safe to evaluate at most once per invocation, in argument position. Implementations should be side effect free, as this method may be called more than once for the same parameter.

Specified by:

defaultValueExpression in interface ParameterDefaultValueProvider

Parameters:

parameter - The parameter, for which ParameterElement.hasDefault() is true

target - The receiver of the call the parameter belongs to, or null when the default is obtained without one — as for a constructor, or where the language emits a static accessor

Returns:

The expression, or Optional.empty() if the default cannot be materialised at the call site, in which case the caller falls back to the default value of the parameter's type