1 files changed, 125 insertions, 0 deletions
diff --git a/main/test/src/define/ApplicativeTests.scala b/main/test/src/define/ApplicativeTests.scala
new file mode 100644
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--- /dev/null
+++ b/main/test/src/define/ApplicativeTests.scala
@@ -0,0 +1,125 @@
+package mill.define
+
+import mill.api.Ctx.ImplicitStub
+import utest._
+
+import scala.annotation.compileTimeOnly
+import scala.language.experimental.macros
+
+
+object ApplicativeTests extends TestSuite {
+  implicit def optionToOpt[T](o: Option[T]): Opt[T] = new Opt(o)
+  class Opt[T](val self: Option[T]) extends Applicative.Applyable[Option, T]
+  object Opt extends OptGenerated with Applicative.Applyer[Opt, Option, Applicative.Id, String]{
+
+    val injectedCtx = "helloooo"
+    def underlying[A](v: Opt[A]) = v.self
+    def apply[T](t: T): Option[T] = macro Applicative.impl[Option, T, String]
+
+    def mapCtx[A, B](a: Option[A])(f: (A, String) => B): Option[B] = a.map(f(_, injectedCtx))
+    def zip() = Some(())
+    def zip[A](a: Option[A]) = a.map(Tuple1(_))
+  }
+  class Counter{
+    var value = 0
+    def apply() = {
+      value += 1
+      value
+    }
+  }
+  @compileTimeOnly("Target.ctx() can only be used with a T{...} block")
+  @ImplicitStub
+  implicit def taskCtx: String = ???
+
+  val tests = Tests{
+
+    'selfContained - {
+
+      'simple - assert(Opt("lol " + 1) == Some("lol 1"))
+      'singleSome - assert(Opt("lol " + Some("hello")()) == Some("lol hello"))
+      'twoSomes - assert(Opt(Some("lol ")() + Some("hello")()) == Some("lol hello"))
+      'singleNone - assert(Opt("lol " + None()) == None)
+      'twoNones - assert(Opt("lol " + None() + None()) == None)
+    }
+    'context - {
+      assert(Opt(Opt.ctx() + Some("World")()) == Some("hellooooWorld"))
+    }
+    'capturing - {
+      val lol = "lol "
+      def hell(o: String) = "hell" + o
+      'simple - assert(Opt(lol + 1) == Some("lol 1"))
+      'singleSome - assert(Opt(lol + Some(hell("o"))()) == Some("lol hello"))
+      'twoSomes - assert(Opt(Some(lol)() + Some(hell("o"))()) == Some("lol hello"))
+      'singleNone - assert(Opt(lol + None()) == None)
+      'twoNones - assert(Opt(lol + None() + None()) == None)
+    }
+    'allowedLocalDef - {
+      // Although x is defined inside the Opt{...} block, it is also defined
+      // within the LHS of the Applyable#apply call, so it is safe to life it
+      // out into the `zipMap` arguments list.
+      val res = Opt{ "lol " + Some("hello").flatMap(x => Some(x)).apply() }
+      assert(res == Some("lol hello"))
+    }
+    'upstreamAlwaysEvaluated - {
+      // Whether or not control-flow reaches the Applyable#apply call inside an
+      // Opt{...} block, we always evaluate the LHS of the Applyable#apply
+      // because it gets lifted out of any control flow statements
+      val counter = new Counter()
+      def up = Opt{ "lol " + counter() }
+      val down = Opt{ if ("lol".length > 10) up() else "fail" }
+      assert(
+        down == Some("fail"),
+        counter.value == 1
+      )
+    }
+    'upstreamEvaluatedOnlyOnce - {
+      // Even if control-flow reaches the Applyable#apply call more than once,
+      // it only gets evaluated once due to its lifting out of the Opt{...} block
+      val counter = new Counter()
+      def up = Opt{ "lol " + counter() }
+      def runTwice[T](t: => T) = (t, t)
+      val down = Opt{ runTwice(up()) }
+      assert(
+        down == Some(("lol 1", "lol 1")),
+        counter.value == 1
+      )
+    }
+    'evaluationsInsideLambdasWork - {
+      // This required some fiddling with owner chains inside the macro to get
+      // working, so ensure it doesn't regress
+      val counter = new Counter()
+      def up = Opt{ "hello" + counter() }
+      val down1 = Opt{ (() => up())() }
+      val down2 = Opt{ Seq(1, 2, 3).map(n => up() * n) }
+      assert(
+        down1 == Some("hello1"),
+        down2 == Some(Seq("hello2", "hello2hello2", "hello2hello2hello2"))
+      )
+    }
+    'appliesEvaluatedOncePerLexicalCallsite - {
+      // If you have multiple Applyable#apply() lexically in the source code of
+      // your Opt{...} call, each one gets evaluated once, even if the LHS of each
+      // apply() call is identical. It's up to the downstream zipMap()
+      // implementation to decide if it wants to dedup them or do other things.
+      val counter = new Counter()
+      def up = Opt{ "hello" + counter() }
+      val down = Opt{ Seq(1, 2, 3).map(n => n + up() + up()) }
+      assert(down == Some(Seq("1hello1hello2", "2hello1hello2", "3hello1hello2")))
+    }
+    'appliesEvaluateBeforehand - {
+      // Every Applyable#apply() within a Opt{...} block evaluates before any
+      // other logic within that block, even if they would happen first in the
+      // normal Scala evaluation order
+      val counter = new Counter()
+      def up = Opt{ counter() }
+      val down = Opt{
+        val res = counter()
+        val one = up()
+        val two = up()
+        val three = up()
+        (res, one, two, three)
+      }
+      assert(down == Some((4, 1, 2, 3)))
+    }
+  }
+}