From 970be9feabdb2d9fb7f789d0e091a728c947df0f Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Sat, 27 Apr 2019 20:40:31 -0700
Subject: [PATCH] Support rest parameters in function signatures

---
 src/utils/__tests__/getFlowType-test.js | 15 +++++++++++++--
 src/utils/__tests__/getTSType-test.js   | 14 ++++++++++++--
 src/utils/getFlowType.js                | 17 +++++++++++++++--
 src/utils/getTSType.js                  | 13 ++++++++++---
 4 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/src/utils/__tests__/getFlowType-test.js b/src/utils/__tests__/getFlowType-test.js
index 177b848784f..dacbe24ca39 100644
--- a/src/utils/__tests__/getFlowType-test.js
+++ b/src/utils/__tests__/getFlowType-test.js
@@ -216,7 +216,9 @@ describe('getFlowType', () => {
   });
 
   it('detects function signature type', () => {
-    const typePath = expression('x: (p1: number, p2: ?string) => boolean')
+    const typePath = expression(
+      'x: (p1: number, p2: ?string, ...rest: Array<string>) => boolean',
+    )
       .get('typeAnnotation')
       .get('typeAnnotation');
     expect(getFlowType(typePath)).toEqual({
@@ -226,10 +228,18 @@ describe('getFlowType', () => {
         arguments: [
           { name: 'p1', type: { name: 'number' } },
           { name: 'p2', type: { name: 'string', nullable: true } },
+          {
+            name: 'rest',
+            type: {
+              name: 'Array',
+              elements: [{ name: 'string' }],
+              raw: 'Array<string>',
+            },
+          },
         ],
         return: { name: 'boolean' },
       },
-      raw: '(p1: number, p2: ?string) => boolean',
+      raw: '(p1: number, p2: ?string, ...rest: Array<string>) => boolean',
     });
   });
 
@@ -265,6 +275,7 @@ describe('getFlowType', () => {
       raw: 'string => boolean',
     });
   });
+
   it('detects callable signature type', () => {
     const typePath = expression('x: { (str: string): string, token: string }')
       .get('typeAnnotation')
diff --git a/src/utils/__tests__/getTSType-test.js b/src/utils/__tests__/getTSType-test.js
index 3248647d09f..b3a1955d5c8 100644
--- a/src/utils/__tests__/getTSType-test.js
+++ b/src/utils/__tests__/getTSType-test.js
@@ -185,7 +185,9 @@ describe('getTSType', () => {
   });
 
   it('detects function signature type', () => {
-    const typePath = expression('x: (p1: number, p2: string) => boolean')
+    const typePath = expression(
+      'x: (p1: number, p2: string, ...rest: Array<string>) => boolean',
+    )
       .get('typeAnnotation')
       .get('typeAnnotation');
     expect(getTSType(typePath)).toEqual({
@@ -195,10 +197,18 @@ describe('getTSType', () => {
         arguments: [
           { name: 'p1', type: { name: 'number' } },
           { name: 'p2', type: { name: 'string' } },
+          {
+            name: 'rest',
+            type: {
+              name: 'Array',
+              elements: [{ name: 'string' }],
+              raw: 'Array<string>',
+            },
+          },
         ],
         return: { name: 'boolean' },
       },
-      raw: '(p1: number, p2: string) => boolean',
+      raw: '(p1: number, p2: string, ...rest: Array<string>) => boolean',
     });
   });
 
diff --git a/src/utils/getFlowType.js b/src/utils/getFlowType.js
index 8dff69f7ef0..21dd2f5bf24 100644
--- a/src/utils/getFlowType.js
+++ b/src/utils/getFlowType.js
@@ -266,14 +266,27 @@ function handleFunctionTypeAnnotation(
 
   path.get('params').each(param => {
     const typeAnnotation = getTypeAnnotation(param);
-    if (!typeAnnotation) return;
 
     type.signature.arguments.push({
       name: param.node.name ? param.node.name.name : '',
-      type: getFlowTypeWithResolvedTypes(typeAnnotation, typeParams),
+      type: typeAnnotation
+        ? getFlowTypeWithResolvedTypes(typeAnnotation, typeParams)
+        : null,
     });
   });
 
+  if (path.node.rest) {
+    const rest = path.get('rest');
+    const typeAnnotation = getTypeAnnotation(rest);
+
+    type.signature.arguments.push({
+      name: rest.node.name ? rest.node.name.name : '',
+      type: typeAnnotation
+        ? getFlowTypeWithResolvedTypes(typeAnnotation, typeParams)
+        : null,
+    });
+  }
+
   return type;
 }
 
diff --git a/src/utils/getTSType.js b/src/utils/getTSType.js
index f9d020fc49c..5eb38a02884 100644
--- a/src/utils/getTSType.js
+++ b/src/utils/getTSType.js
@@ -30,6 +30,7 @@ const tsTypes = {
   TSAnyKeyword: 'any',
   TSBooleanKeyword: 'boolean',
   TSUnknownKeyword: 'unknown',
+  TSNeverKeyword: 'never',
   TSNullKeyword: 'null',
   TSUndefinedKeyword: 'undefined',
   TSNumberKeyword: 'number',
@@ -227,11 +228,17 @@ function handleTSFunctionType(
 
   path.get('parameters').each(param => {
     const typeAnnotation = getTypeAnnotation(param);
-    if (!typeAnnotation) return;
+
+    let name = param.node.name || '';
+    if (param.node.type === 'RestElement') {
+      name = param.node.argument.name;
+    }
 
     type.signature.arguments.push({
-      name: param.node.name || '',
-      type: getTSTypeWithResolvedTypes(typeAnnotation, typeParams),
+      name,
+      type: typeAnnotation
+        ? getTSTypeWithResolvedTypes(typeAnnotation, typeParams)
+        : null,
     });
   });