From 08dc16aa4b794fd0b924679e0aabc2b8a58854bf Mon Sep 17 00:00:00 2001
From: Paul Loyd <pavelko95@gmail.com>
Date: Wed, 29 Nov 2017 01:16:29 +0300
Subject: [PATCH] Add support for $ReadOnly and $Exact

---
 src/globals.js              | 13 +++++++++++++
 tests/samples/exact.js      | 10 ++++++++++
 tests/samples/exact.json    | 24 ++++++++++++++++++++++++
 tests/samples/readOnly.js   | 10 ++++++++++
 tests/samples/readOnly.json | 24 ++++++++++++++++++++++++
 5 files changed, 81 insertions(+)
 create mode 100644 tests/samples/exact.js
 create mode 100644 tests/samples/exact.json
 create mode 100644 tests/samples/readOnly.js
 create mode 100644 tests/samples/readOnly.json

diff --git a/src/globals.js b/src/globals.js
index cb92be9..9d1046d 100644
--- a/src/globals.js
+++ b/src/globals.js
@@ -93,6 +93,14 @@ function shape(params: (?Type)[], resolve: TypeId => Type): ?Type {
     };
 }
 
+function unwrap(params: (?Type)[]): ?Type {
+    invariant(params.length === 1);
+
+    const [type] = params;
+
+    return type ? clone(type) : null;
+}
+
 export default {
     Object: object,
     Buffer: buffer,
@@ -102,4 +110,9 @@ export default {
     $ElementType: elemType,
     $NonMaybeType: stripMaybe,
     $Shape: shape,
+    $ReadOnly: unwrap,
+    $Exact: unwrap, // TODO: another semantic for exact types?
+    // TODO: $Keys
+    // TODO: $Values
+    // TODO: $Diff
 };
diff --git a/tests/samples/exact.js b/tests/samples/exact.js
new file mode 100644
index 0000000..e436c26
--- /dev/null
+++ b/tests/samples/exact.js
@@ -0,0 +1,10 @@
+type X = {
+    x: string;
+    y: boolean;
+}
+
+type Y = $Exact<X>;
+
+type Z = $Exact<{z: string}>;
+
+export type {Y, Z};
diff --git a/tests/samples/exact.json b/tests/samples/exact.json
new file mode 100644
index 0000000..b399291
--- /dev/null
+++ b/tests/samples/exact.json
@@ -0,0 +1,24 @@
+{
+    "types": [
+        {
+            "id": ["exact", "X"],
+            "kind": "record",
+            "fields": [
+                {"name": "x", "value": {"kind": "string"}, "required": true},
+                {"name": "y", "value": {"kind": "boolean"}, "required": true}
+            ]
+        },
+        {
+            "id": ["exact", "Y"],
+            "kind": "reference",
+            "to": ["exact", "X"]
+        },
+        {
+            "id": ["exact", "Z"],
+            "kind": "record",
+            "fields": [
+                {"name": "z", "value": {"kind": "string"}, "required": true}
+            ]
+        }
+    ]
+}
diff --git a/tests/samples/readOnly.js b/tests/samples/readOnly.js
new file mode 100644
index 0000000..c5026a7
--- /dev/null
+++ b/tests/samples/readOnly.js
@@ -0,0 +1,10 @@
+type X = {
+    x: string;
+    y: boolean;
+}
+
+type Y = $ReadOnly<X>;
+
+type Z = $ReadOnly<{z: string}>;
+
+export type {Y, Z};
diff --git a/tests/samples/readOnly.json b/tests/samples/readOnly.json
new file mode 100644
index 0000000..ef99e6b
--- /dev/null
+++ b/tests/samples/readOnly.json
@@ -0,0 +1,24 @@
+{
+    "types": [
+        {
+            "id": ["readOnly", "X"],
+            "kind": "record",
+            "fields": [
+                {"name": "x", "value": {"kind": "string"}, "required": true},
+                {"name": "y", "value": {"kind": "boolean"}, "required": true}
+            ]
+        },
+        {
+            "id": ["readOnly", "Y"],
+            "kind": "reference",
+            "to": ["readOnly", "X"]
+        },
+        {
+            "id": ["readOnly", "Z"],
+            "kind": "record",
+            "fields": [
+                {"name": "z", "value": {"kind": "string"}, "required": true}
+            ]
+        }
+    ]
+}