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add-compiler-option

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Adds a new compiler option to Metro.

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How to use this skill

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  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
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Source SKILL.md: https://github.com/ZacSweers/metro/blob/HEAD/.agents/skills/add-metro-option/SKILL.md

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Files to Update

When adding a new option, you need to update these files in order:

1. compiler/src/main/kotlin/dev/zacsweers/metro/compiler/MetroOptions.kt

Add the option in four places:

a. Add enum entry in MetroOption

MY_NEW_OPTION(
  RawMetroOption.boolean(  // or RawMetroOption() for non-boolean types
    name = "my-new-option",  // kebab-case name used in CLI
    defaultValue = false,
    valueDescription = "<true | false>",
    description = "Description of what this option does.",
    required = false,
    allowMultipleOccurrences = false,
  )
),

For non-boolean options, use the full RawMetroOption constructor with a valueMapper:

MY_INT_OPTION(
  RawMetroOption(
    name = "my-int-option",
    defaultValue = 10,
    valueDescription = "<count>",
    description = "Description here",
    required = false,
    allowMultipleOccurrences = false,
    valueMapper = { it.toInt() },
  )
),

b. Add property in MetroOptions data class

public val myNewOption: Boolean = MetroOption.MY_NEW_OPTION.raw.defaultValue.expectAs(),

c. Add property in MetroOptions.Builder

public var myNewOption: Boolean = base.myNewOption

d. Add to Builder.build() function

myNewOption = myNewOption,

e. Add to MetroOptions.Companion.load() function

MY_NEW_OPTION -> myNewOption = configuration.getAsBoolean(entry)

For non-boolean types, use the appropriate helper:

  • configuration.getAsString(entry) for String
  • configuration.getAsInt(entry) for Int
  • configuration.getAsSet(entry) for Set types

2. gradle-plugin/src/main/kotlin/dev/zacsweers/metro/gradle/MetroPluginExtension.kt

Add a Gradle DSL property:

/**
 * KDoc description of what this option does.
 *
 * Disabled by default.
 */
public val myNewOption: Property<Boolean> =
  objects.booleanProperty("metro.myNewOption", false)

For options that should support Gradle properties:

objects.booleanProperty("metro.propertyName", defaultValue)

For options without Gradle property support:

objects.property(Boolean::class.java).convention(false)

3. gradle-plugin/src/main/kotlin/dev/zacsweers/metro/gradle/MetroGradleSubplugin.kt

In applyToCompilation, add to the options list:

add(lazyOption("my-new-option", extension.myNewOption))

Note: The option name here must match the name in RawMetroOption.

4. compiler/src/test/kotlin/dev/zacsweers/metro/compiler/MetroCompilerTest.kt

In toPluginOptions(), add handling for the new option:

MetroOption.MY_NEW_OPTION -> {
  processor.option(entry.raw.cliOption, myNewOption)
}

5. (Optional) compiler-tests/src/test/kotlin/dev/zacsweers/metro/compiler/MetroDirectives.kt

Only needed if the option should be controllable from test directives:

val MY_NEW_OPTION by
  valueDirective("Description of the directive.") { it.toBoolean() }

Or for simple on/off directives:

val MY_NEW_OPTION by directive("Description of the directive.")

Option Types

  • Boolean: Use RawMetroOption.boolean() helper
  • Int: Use RawMetroOption() with valueMapper = { it.toInt() }
  • String: Use RawMetroOption() with valueMapper = { it }
  • Enum: Use RawMetroOption() with valueMapper = { it } and parse in load()
  • Set: Use RawMetroOption() with valueMapper = { it.splitToSequence(':').mapToSet { ClassId.fromString(it, false) } }

Naming Conventions

  • Enum entry: SCREAMING_SNAKE_CASE
  • CLI option name: kebab-case
  • Kotlin property: camelCase
  • Gradle property: metro.camelCase

Annotations

  • Use @DelicateMetroGradleApi for experimental options
  • Use @Deprecated for options that will be removed