Support factory methods using generics (ktlint-ruleset-standard)

[sya-ri]

Expected Behavior

class Generics<T>(val value: T)

// Error
fun <T> Generics(action: () -> T): Generics<T> = Generics(action())

Expect this code to not error.

ASTNode.isFactoryMethod() needs to be improved.

it.name == it.typeReference?.text

it.name is a method name, and it.typeReference?.text includes generics, so there will be a mismatch.

---

As a problem related to factory methods, even one-liners that use the expression body will result in an error. Since this is an avoidable problem and difficult to analyze, I don't think it's necessary to deal with it.

class NoGenerics(val value: String)

// Error
fun NoGenerics(value: Double) = NoGenerics(value.toString())

Observed Behavior

15:28:16.167 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered RuleSetProviderV3 with id 'standard' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'baseline' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'plain' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'checkstyle' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'json' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'format' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'html' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'plain-summary' in ktlint JAR
15:28:16.392 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintServiceLoader - Discovered ReporterProviderV2 with id 'sarif' in ktlint JAR
15:28:16.393 [main] DEBUG com.pinterest.ktlint.cli.internal.ReporterAggregator - Initializing "plain" reporter with {plain=true, color=false, color_name=DARK_GRAY, format=false}
15:28:16.398 [main] DEBUG com.pinterest.ktlint.cli.internal.FileUtils - Start walkFileTree from directory: 'C:\Users\gbv_s\IdeaProjects\ktlint-function-naming-factory-method-bug'
15:28:16.411 [main] DEBUG com.pinterest.ktlint.cli.internal.FileUtils - Discovered 3 files to be processed in 12 ms
15:28:16.429 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Starting with linting file 'settings.gradle.kts'
15:28:16.429 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Starting with linting file 'build.gradle.kts'
15:28:16.429 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Starting with linting file 'Main.kt'
15:28:16.790 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.EditorConfigLoader - Effective editorconfig properties for file 'C:\Users\gbv_s\IdeaProjects\ktlint-function-naming-factory-method-bug\src\main\kotlin\Main.kt':
	
15:28:16.790 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.EditorConfigLoader - Effective editorconfig properties for file 'C:\Users\gbv_s\IdeaProjects\ktlint-function-naming-factory-method-bug\build.gradle.kts':
	
15:28:16.790 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.EditorConfigLoader - Effective editorconfig properties for file 'C:\Users\gbv_s\IdeaProjects\ktlint-function-naming-factory-method-bug\settings.gradle.kts':
	
15:28:16.803 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.803 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.803 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.803 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.803 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:argument-list-wrapping' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.804 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.805 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.805 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.internal.rulefilter.RunAfterRuleFilter - Rule with id 'standard:indent' should run after the rule with id 'standard:class-signature'. However, the latter rule is not loaded and is allowed to be ignored. For best results, it is advised load the rule.
15:28:16.815 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.internal.RuleProviderSorter - Rules will be executed in order below:
           - internal:ktlint-suppression, 
           - standard:annotation-spacing, 
           - standard:blank-line-before-declaration, 
           - standard:chain-wrapping, 
           - standard:class-naming, 
           - standard:colon-spacing, 
           - standard:comma-spacing, 
           - standard:comment-spacing, 
           - standard:comment-wrapping, 
           - standard:context-receiver-wrapping, 
           - standard:curly-spacing, 
           - standard:discouraged-comment-location, 
           - standard:dot-spacing, 
           - standard:double-colon-spacing, 
           - standard:enum-entry-name-case, 
           - standard:enum-wrapping, 
           - standard:filename, 
           - standard:final-newline, 
           - standard:fun-keyword-spacing, 
           - standard:function-naming, 
           - standard:function-return-type-spacing, 
           - standard:function-start-of-body-spacing, 
           - standard:function-type-reference-spacing, 
           - standard:if-else-bracing, 
           - standard:import-ordering, 
           - standard:kdoc-wrapping, 
           - standard:keyword-spacing, 
           - standard:modifier-list-spacing, 
           - standard:modifier-order, 
           - standard:multiline-expression-wrapping, 
           - standard:multiline-if-else, 
           - standard:no-blank-line-before-rbrace, 
           - standard:no-blank-line-in-list, 
           - standard:no-blank-lines-in-chained-method-calls, 
           - standard:no-consecutive-blank-lines, 
           - standard:no-consecutive-comments, 
           - standard:no-empty-class-body, 
           - standard:no-empty-file, 
           - standard:no-empty-first-line-in-class-body, 
           - standard:no-empty-first-line-in-method-block, 
           - standard:no-line-break-after-else, 
           - standard:no-line-break-before-assignment, 
           - standard:no-multi-spaces, 
           - standard:no-trailing-spaces, 
           - standard:no-unit-return, 
           - standard:no-unused-imports, 
           - standard:no-wildcard-imports, 
           - standard:nullable-type-spacing, 
           - standard:op-spacing, 
           - standard:package-name, 
           - standard:parameter-list-spacing, 
           - standard:parameter-list-wrapping, 
           - standard:parameter-wrapping, 
           - standard:paren-spacing, 
           - standard:property-naming, 
           - standard:property-wrapping, 
           - standard:range-spacing, 
           - standard:spacing-around-angle-brackets, 
           - standard:spacing-between-declarations-with-annotations, 
           - standard:spacing-between-declarations-with-comments, 
           - standard:spacing-between-function-name-and-opening-parenthesis, 
           - standard:statement-wrapping, 
           - standard:string-template, 
           - standard:try-catch-finally-spacing, 
           - standard:type-argument-list-spacing, 
           - standard:type-parameter-list-spacing, 
           - standard:unary-op-spacing, 
           - standard:unnecessary-parentheses-before-trailing-lambda, 
           - standard:annotation, 
           - standard:if-else-wrapping, 
           - standard:no-single-line-block-comment, 
           - standard:wrapping, 
           - standard:argument-list-wrapping, 
           - standard:no-semi, 
           - standard:function-signature, 
           - standard:trailing-comma-on-call-site, 
           - standard:trailing-comma-on-declaration-site, 
           - standard:indent, 
           - standard:block-comment-initial-star-alignment, 
           - standard:string-template-indent, 
           - standard:max-line-length
15:28:16.990 [pool-1-thread-2] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Finished with linting file 'settings.gradle.kts'
15:28:16.991 [pool-1-thread-1] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Finished with linting file 'build.gradle.kts'
15:28:17.017 [pool-1-thread-3] DEBUG com.pinterest.ktlint.rule.engine.api.KtLintRuleEngine - Finished with linting file 'Main.kt'
C:/Users/gbv_s/IdeaProjects/ktlint-function-naming-factory-method-bug/src/main/kotlin/Main.kt:12:5: Function name should start with a lowercase letter (except factory methods) and use camel case (standard:function-naming)
C:/Users/gbv_s/IdeaProjects/ktlint-function-naming-factory-method-bug/src/main/kotlin/Main.kt:15:9: Function name should start with a lowercase letter (except factory methods) and use camel case (standard:function-naming)

Summary error count (descending) by rule:
  standard:function-naming: 2
15:28:17.019 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintCommandLine - Finished processing in 864ms / 3 file(s) scanned / 2 error(s) found
15:28:17.019 [main] DEBUG com.pinterest.ktlint.cli.internal.KtlintCommandLine - Exit ktlint with exit code: 1

Steps to Reproduce

https://github.com/sya-ri/ktlint-function-naming-factory-method-bug

class NoGenerics(val value: String)

class Generics<T>(val value: T)

// No error
fun NoGenerics(value: Int): NoGenerics = NoGenerics(value.toString())

// No error
fun <T> NoGenerics(value: T): NoGenerics = NoGenerics(value.toString())

// Error: support one-liner
fun NoGenerics(value: Double) = NoGenerics(value.toString())

// Error
fun <T> Generics(action: () -> T): Generics<T> = Generics(action())

Your Environment

• Version of ktlint used: 1.1.0-kotlin-dev-SNAPSHOT (ktlint-cli-1.1.0-kotlin-dev-20231106.165144-8.jar)
• Relevant parts of the .editorconfig settings
• Name and version (or code for custom task) of integration used (Gradle plugin, Maven plugin, command line, custom Gradle task): custom Gradle task
• Version of Gradle used (if applicable): 8.2
• Operating System and version: Windows 11 Home / 23H2 / 22631.2506

[paul-dingemans]

Thnx for reporting and examples. I will investigate.

[paul-dingemans]

// Error: support one-liner
fun NoGenerics(value: Double) = NoGenerics(value.toString())

I do see value in supporting this. I have added a kind of 'lame' implementation for this which allows exactly this example. So in this way an overload of a class constructor or another factory method can be made without having to specify the type explitcitly.

[paul-dingemans]

Reference from PR #2553 is to be ignored for this issue.