Forbid accessing blocking functions

lib/src/test/kotlin/graphql/nadel/archunit/ArchUnitUtil.kt

@@ -0,0 +1,7 @@
+package graphql.nadel.archunit
+
+import com.tngtech.archunit.core.domain.JavaClass
+
+inline fun <reified T : Any> JavaClass.isAssignableTo(): Boolean {
+    return isAssignableTo(T::class.java)
+}

lib/src/test/kotlin/graphql/nadel/archunit/NioArchTest.kt

@@ -0,0 +1,36 @@
+package graphql.nadel.archunit
+
+import com.tngtech.archunit.base.DescribedPredicate
+import com.tngtech.archunit.core.domain.JavaAccess
+import com.tngtech.archunit.core.importer.ClassFileImporter
+import com.tngtech.archunit.core.importer.ImportOption
+import com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses
+import org.junit.jupiter.api.Test
+import java.util.concurrent.Future
+
+class NioArchTest {
+    @Test
+    fun `does not use blocking functions`() {
+        val importedClasses = ClassFileImporter()
+            .withImportOption(ImportOption.DoNotIncludeTests())
+            .importPackages("graphql.nadel")
+
+        val rule = noClasses()
+            .should()
+            .accessTargetWhere(
+                object : DescribedPredicate<JavaAccess<*>>("access blocking functions") {
+                    override fun test(t: JavaAccess<*>): Boolean {
+                        // Java Future
+                        if (t.target.owner.isAssignableTo<Future<*>>()) {
+                            return t.target.name == "get"
+                        }
+
+                        // Coroutines. Use startsWith because sometimes the function is runBlocking$default
+                        return t.target.name.startsWith("runBlocking")
+                    }
+                }
+            )
+
+        rule.check(importedClasses)
+    }
+}