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Migration Guide Cleanup #7001

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Jun 28, 2022
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Migration Guide Cleanup #7001

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34 changes: 17 additions & 17 deletions docs/guides/migrate/migration-guide.md
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Original file line number Diff line number Diff line change
Expand Up @@ -382,7 +382,7 @@ In ZIO 2.x, when we are zipping together different effects:
- `Tuple`s are not nested.
- `Unit`s do not contribute to the output.

Assume we have these effects
Assume we have these effects:

```scala mdoc:silent:nest
val x1: UIO[Int] = ZIO.succeed(???)
Expand All @@ -393,15 +393,16 @@ val x4: UIO[Boolean] = ZIO.succeed(???)

In ZIO 1.x, the output of zipping together these effects are nested:

```scala
```scala mdoc:compile-only
val zipped = x1 <*> x2 <*> x3 <*> x4
// zipped: ZIO[Any, Nothing, (((Int, Unit), String), Boolean)] = zio.ZIO$FlatMap@3ed3c202
// zipped: ZIO[Any, Nothing, (((Int, Unit), String), Boolean)] = ...
```

While in ZIO 2.x, we have more ergonomics result type and also the `Unit` data-type doesn't contribute to the output:

```scala mdoc:nest
```scala mdoc:compile-only
val zipped = x1 <*> x2 <*> x3 <*> x4
// zipped: ZIO[Any, Nothing, (Int, String, Boolean)] = ...
```

This change is not only for the `ZIO` data type but also for all other data types like `ZStream`, `ZSTM`, etc.
Expand Down Expand Up @@ -473,7 +474,7 @@ The error channel of `leftProjection` doesn't contain type information of the ot

In ZIO 2.x, the `ZIO#left` and `ZIO#right`, contains all type information so then we can `unleft` or `unright` to inverse that projection:

```scala mdoc:nest
```scala mdoc:compile-only
val effect = ZIO.attempt(Left[Int, String](5))
val leftProjection = effect.left
val unlefted = leftProjection.map(_ * 2).unleft
Expand Down Expand Up @@ -588,8 +589,8 @@ for {
2. By removing these services from the environment, all usage of `ZEnv`, `Console`, `Clock`, `Random`, or `System` in the environment type of `ZIO`, `ZStream` and `ZLayer` should be generally deleted:

```diff
val myApp: ZIO[Clock with Console with Random with UserRepo with Logging, IOException, Unit] = ???
val myApp: ZIO[UserRepo with Logging, IOException, Unit] = ???
- val myApp: ZIO[Clock with Console with Random with UserRepo with Logging, IOException, Unit] = ???
+ val myApp: ZIO[UserRepo with Logging, IOException, Unit] = ???
```

3. If we want to use the live version in tests we can use these test aspects instead of providing them as layers:
Expand Down Expand Up @@ -2057,13 +2058,13 @@ Even though highly polymorphic versions of ZIO concurrent data structures (e.g.

Therefore, we simplified these data structures by specializing them in their more monomorphic versions without significant loss of features:

| ZIO 1.x (removed) | ZIO 2.x |
|-------------------------------------|----------------------|
|`ZRef[+EA, +EB, -A, +B]` | `Ref[A]` |
|`ZTRef[+EA, +EB, -A, +B]` | `TRef[A]` |
|`ZRefM[-RA, -RB, +EA, +EB, -A, +B]` | `Ref.Synchronized[A]`|
|`ZQueue[-RA, -RB, +EA, +EB, -A, +B]` | `Queue[A]` |
|`ZHub[-RA, -RB, +EA, +EB, -A, +B]` | `Hub[A]` |
| ZIO 1.x (removed) | ZIO 2.x |
|--------------------------------------|-----------------------|
| `ZRef[+EA, +EB, -A, +B]` | `Ref[A]` |
| `ZTRef[+EA, +EB, -A, +B]` | `TRef[A]` |
| `ZRefM[-RA, -RB, +EA, +EB, -A, +B]` | `Ref.Synchronized[A]` |
| `ZQueue[-RA, -RB, +EA, +EB, -A, +B]` | `Queue[A]` |
| `ZHub[-RA, -RB, +EA, +EB, -A, +B]` | `Hub[A]` |

## Ref

Expand Down Expand Up @@ -2449,10 +2450,9 @@ Every data type in ZIO (`ZIO`, `ZStream`, etc.) has a variety of constructor fun

While these are precise, ZIO 2.0 provides the `ZIO.from` constructor which can intelligently choose the most likely constructor based on the input type. So instead of writing `ZIO.fromEither(Right(3))` we can easily write `ZIO.from(Right(3))`. Let's try some of them:

```scala mdoc:invisible
```scala mdoc:compile-only
import zio.stream.ZStream
```
```scala mdoc:nest

ZIO.fromOption(Some("Ok!"))
ZIO.from(Some("Ok!"))

Expand Down