kotlinlang #dsl

file ourselves. Using https://editor.swagger.io/ eased the pain, especially since it provides validation errors and code completion. Now I wonder whether I could write a Kotlin DSL for OpenAPI, and generate the

swagger.yaml

on the fly. So the initial results look tempting, as I can write:

openapi {
    openapi { "3.0.1" }
    info {
        title { "Swagger Petstore" }
        version { "1.0.0" }
    }
}

But there are two things I dislike with this solution. One: I have to write a lot of code to get this basic functionality. And two: Nobody prevents me from calling

info

title

multiple times, or even omitting them totally. For example, this would be invalid:

openapi {
    info {
        title { "Swagger Petstore" }
        title { "Swagger Petstore 2" }
        version { "1.0.0" }
    }
}

In contrast, writing the OpenAPI spec with data classes gains me more functionality than writing a custom DSL:

Document(
        openapi = "3.0.1",
        info = Info(
                title = "Swagger Petstore",
                version = "1.0.0"
        )
)

Here I have to add

openapi

and

info

because they are both required, and IntelliJ tells me if there is a duplication error. So my question is: What do I gain from writing a DSL in this case, or is the OpenAPI spec not a good use case for it?

helpermethod

01/04/2018, 5:11 PM

Hi, another question: Is it somehow possible to require that a method is called, something like

foo {
    bar("bar") // this is required
    baz() // this is optional
}

kristofdho

01/23/2018, 11:45 AM

this does allow you to change the order of the

doThis

etc calls, not sure if that's a problem

kikitux

02/22/2018, 4:14 PM

Hello, My name is Alvaro, native spanish speaker, sorry if my english is not very good. I am trying to learn a bit on how Kotlin for DSL fits, however the DSL concept in itself is new to me, so if anyone can point me to any resource that can help me to understand what a DSL is, so i can understand the benefits will help me to move into the next step that is produce a DSL in kotlin

snowe

06/16/2018, 4:42 PM

Yeah I had considered the unaryPlus operator, but then I'd have to define it on

Any

and that definitely isn't a good idea. Wait, unless, can I define

unaryPlus

just in the context of a block?

Dominaezzz

11/13/2018, 10:29 AM

Extension vs member methods for DSLs?

tjb

11/20/2018, 4:44 AM

haha sorry different question: is it difficult to use a DSL written in kotlin in a java project?

tjb

11/26/2018, 3:03 AM

fun match(block: MatchBuilder.() -> Unit = {}) {
        val matchBuilder = MatchBuilder()
        matchBuilder.block()
        match = match.plus(matchBuilder.build())
    }

tjb

11/26/2018, 3:10 AM

match {
            optional = false
        }

        with {
            "hello, world"
        }

Marc Knaup

01/08/2019, 11:04 AM

Hey guys, is there a way to disable parameter name hints using an annotation so that I can write a DSL which doesn’t show any of these hint?

🙁 1

🇳🇴 2

digitalsanctum

01/14/2019, 8:06 PM

Does anyone have an example project to share that has good constructs for Java (builders for Java, data classes for Kotlin). I'm wondering if the pattern is to just create builders in addition to data class constructors using named params, default values, etc.

Marc Reichelt

01/28/2019, 12:44 PM

Mainly, the

Configuration

class does not have an

isDirectory

property - but how could the Groovy code then work in the first place?

GarouDan

01/29/2019, 1:10 AM

If we have something like

group "com.company.team.project"
version "0.0.1"

in our

build.gradle

how can we convert this to a

build.gradle.kts

file? I tried something like:

group("com.company.team.project")
version("0.0.1")

but it didn’t work.

ribesg

01/29/2019, 10:07 AM

Anyone else has intense freezes and lags when editing Gradle Kotlin DSL files?

➕ 1

snowe

01/31/2019, 6:05 PM

what is the kotlin dsl equivalent of

api()

? I thought it might be

apiElements

but then the module that uses

apiElements

fails to find the symbols in that jar.

GarouDan

02/09/2019, 8:47 PM

It looks like this call

System.getProperty("configuration.build.dir")

is not right. It is returning null but I could verify that a non empty value is passed in xcode.

GarouDan

02/11/2019, 11:09 PM

Guys, I’m trying to translate this excerpt

jsJar.dependsOn(populateWebFolder)

from a

build.gradle

file to a

build.gradle.kts

. How can I do this? This is part of:

def webFolder = new File(project.buildDir, "../src/jsMain/web")
def jsCompilations = kotlin.targets.js.compilations

task populateWebFolder(dependsOn: [jsMainClasses]) {
    doLast {
        copy {
            from jsCompilations.main.output
            from kotlin.sourceSets.jsMain.resources.srcDirs
            jsCompilations.test.runtimeDependencyFiles.each {
                if (it.exists() && !it.isDirectory()) {
                    from zipTree(it.absolutePath).matching { include '*.js' }
                }
            }
            into webFolder
        }
    }
}

jsJar.dependsOn(populateWebFolder)

task run(type: JavaExec, dependsOn: [jvmMainClasses, jsJar]) {
    main = "sample.SampleJvmKt"
    classpath { [
            kotlin.targets.jvm.compilations.main.output.allOutputs.files,
            configurations.jvmRuntimeClasspath,
    ] }
    args = []
}

GarouDan

02/25/2019, 6:29 PM

Hi, does someone know how can I translate this task to

build.gradle.kts

compileTestKotlin2Js {
    kotlinOptions.metaInfo = true
    kotlinOptions.outputFile = "$project.buildDir.path/js-tests/${project.name}-tests.js"
    kotlinOptions.sourceMap = true
    kotlinOptions.moduleKind = 'commonjs'
//    kotlinOptions.moduleName = project.name + "-test"
    kotlinOptions.main = "call"
}

This one here I could do something like:

compileKotlin2Js {
    kotlinOptions.metaInfo = true
    kotlinOptions.outputFile = "$project.buildDir.path/js/${project.name}.js"
    kotlinOptions.sourceMap = true
    kotlinOptions.moduleKind = 'commonjs'
    kotlinOptions.main = "call"
}

tasks.withType<Kotlin2JsCompile> {
	kotlinOptions {
		//		languageVersion = "1.3"
		metaInfo = true
		outputFile = "${project.buildDir.path}/js/${project.name}.js"
		sourceMap = true
		sourceMapEmbedSources = "always"
		moduleKind = "commonjs" // umd
		main = "call"
	}
}

Marc Knaup

02/25/2019, 8:03 PM

Is this repo still relevant? https://github.com/gradle/kotlin-dsl Latest release there: 1.1.3 Latest release in Gradle Plugin Repo: 1.2.2 #confusing

Kirill Grouchnikov

03/28/2019, 6:13 PM

How would I even know that I can type + something

mgrzechocinski

04/12/2019, 7:11 AM

Hi. Would it be recorded?

Marc Reichelt

05/01/2019, 12:21 PM

Does anyone know what’s a good way to migrate Groovy Gradle Logic to Gradle Kotlin DSL? For example, I’m a little stuck on this one - even with code completion from Kotlin DSL (which is awesome!) I don’t know how I would migrate this: https://github.com/grpc/grpc-java/blob/master/examples/example-kotlin/build.gradle#L43-L51

Marc Knaup

05/08/2019, 10:04 PM

Maybe both channels should be renamed to prevent the confusion 😄

➕ 1

Marc Knaup

05/09/2019, 3:28 PM

There's also confusion about the #gradle channel, so I would rename that too or open it to all Gradle+Kotlin-related questions 🙂

Slackbot

05/22/2019, 6:05 AM

This message was deleted.

mingkangpan

05/26/2019, 2:52 PM

@SqlMarker
object SQLBuilder {
    fun query(init: SqlSelectBuilder.() -> Unit): SqlSelectBuilder {
        val builder = SqlSelectBuilder()
        builder.init()
        return builder
    }
}

08/12/2019, 6:02 PM

I have a DSL function whose lambda returns

Any?

allowing any object to be returned. This lambda's receiver is also a DSL type meaning there are functions you can call inside of it. The problem is that these functions return

Unit

thus completing the contract of the enclosing lambda and avoiding the need to actually return an object. Is there any way to avoid this?

@MyDsl interface Foo {
  fun bar(lambda: Bar.() -> Any?)
}
@MyDsl interface Bar {
  fun someHelper(size: Int)
  fun otherHelper(flag: Boolean)
}

bar {
  someHelper(2)
  otherHelper(true)
  // should be required to return an object here
}

I tried to get clever with an overload of

bar

whose lambda returned

Unit

and was marked as an error, but you can't

@JvmName

an interface function. converting it to a class results in the

Unit

-returned lambda always being preferred. There's a Kotlin-internal annotation to lower its overload precedence, but I don't have access to that.

Shawn

09/05/2019, 5:58 PM

super newb question - does anyone have a blog post or two that collects like DSL best practices? I recently tried my hand at making a simple config-like language for a toy link shortener and am not sure if I put certain things in the right place

benfleis

09/18/2019, 7:16 AM

Hey all, I have used Kotlin a bit here and there, but never really stuck my nose into the DSL opportunities. I have an existing, small custom DSL (perhaps close to a simplified haskell), whose main purpose is to provide a tiny, restrictive language (~40 functions). Is it possible either syntactically, or at compile time, to place heavy restrictions on the allowable functionality within a kotlin DSL? Thus for example, could I prevent basic string manipulation, except through my own pre-defined string manipulation functions? (I suspect this is partially in contrast to typical kotlin/DSL goals, but lack the experience.) Any tips/pointers to related work greatly appreciated. My googling so far has not led to any results.

Marc Knaup

10/04/2019, 7:26 AM

TIL:

someFuncReturningBool() && otherFuncReturningBool()

and

someFuncReturningBool() and otherFuncReturningBool()

is not the same. The former short-circuits, the latter doesn’t. That hit me unexpectedly when I thought “oh that’s nice, I can just use

and

instead of

&&

in my DSL to make it more human-readable”.

rule {
   condition {
      terms.assignmentAddress.isProvided() and
         terms.assignmentAddress.country.isNotSupported() // exception because access not allowed if isProvided() returns false
   }

   issue {
      "Terms: The address of the assignment is located in a country that is not supported."
   }
}

I presume there are only two ways to fix this. a) Use

&&

instead of

and

😥 b) Make all the functions which can be used in

condition {}

that currently return

Boolean

return something like

Condition

instead. That in turn would have an

and

infix operator which makes two

Condition

instances form a new

Condition

and thus allows for chaining with

and

. That would basically build a tree of

Condition

. I guess there are no alternatives for supporting

and

here?

Title

Marc Knaup

10/04/2019, 7:26 AM

TIL:

someFuncReturningBool() && otherFuncReturningBool()

and

someFuncReturningBool() and otherFuncReturningBool()

is not the same. The former short-circuits, the latter doesn’t. That hit me unexpectedly when I thought “oh that’s nice, I can just use

and

instead of

&&

in my DSL to make it more human-readable”.

rule {
   condition {
      terms.assignmentAddress.isProvided() and
         terms.assignmentAddress.country.isNotSupported() // exception because access not allowed if isProvided() returns false
   }

   issue {
      "Terms: The address of the assignment is located in a country that is not supported."
   }
}

I presume there are only two ways to fix this. a) Use

&&

instead of

and

😥 b) Make all the functions which can be used in

condition {}

that currently return

Boolean

return something like

Condition

instead. That in turn would have an

and

infix operator which makes two

Condition

instances form a new

Condition

and thus allows for chaining with

and

. That would basically build a tree of

Condition

. I guess there are no alternatives for supporting

and

here?

efemoney

10/08/2019, 12:46 AM

You have to be careful,

and

is a bitwise operator not a boolean operator.

Marc Knaup

10/08/2019, 3:29 AM

I know. Yet it's defined on

Boolean

, hence the confusion :)

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