From 52549de4b81e3134c536acb75e2af984886e1e2e Mon Sep 17 00:00:00 2001
From: Talha Naqvi <talha.naqvi@shopify.com>
Date: Wed, 23 Feb 2022 15:55:57 -0800
Subject: [PATCH 1/2] cleaned up exceptions and added one for estimated item
 size

---
 src/RecyclerFlatList.tsx    | 30 ++++++++++++++++--------------
 src/errors/CustomError.ts   | 10 ++++++++++
 src/errors/ExceptionList.ts | 15 +++++++++++++++
 3 files changed, 41 insertions(+), 14 deletions(-)
 create mode 100644 src/errors/CustomError.ts
 create mode 100644 src/errors/ExceptionList.ts

diff --git a/src/RecyclerFlatList.tsx b/src/RecyclerFlatList.tsx
index 889827626..d2c162121 100644
--- a/src/RecyclerFlatList.tsx
+++ b/src/RecyclerFlatList.tsx
@@ -19,6 +19,8 @@ import AutoLayoutView, { BlankAreaEventHandler } from "./AutoLayoutView";
 import ItemContainer from "./CellContainer";
 import WrapperComponent from "./WrapperComponent";
 import GridLayoutProviderWithProps from "./GridLayoutProviderWithProps";
+import CustomError from "./errors/CustomError";
+import ExceptionList from "./errors/ExceptionList";
 
 export interface RecyclerFlatListProps<T> extends FlatListProps<T> {
   // TODO: This is to make eslint silent. Out prettier and lint rules are conflicting.
@@ -108,25 +110,25 @@ class RecyclerFlatList<T> extends React.PureComponent<
 
   constructor(props) {
     super(props);
-    this.setup();
-  }
-
-  private setup() {
-    const refreshingPrecondition = !(
-      this.props.onRefresh && typeof this.props.refreshing !== "boolean"
-    );
-    const message =
-      'Invariant Violation: `refreshing` prop must be set as a boolean in order to use `onRefresh`, but got `"undefined"`';
-    invariant(refreshingPrecondition, message);
-    if (this.props.estimatedListSize) {
-      if (this.props.horizontal) {
-        this.listFixedDimensionSize = this.props.estimatedListSize.height;
+    this.validateProps();
+    if (props.estimatedListSize) {
+      if (props.horizontal) {
+        this.listFixedDimensionSize = props.estimatedListSize.height;
       } else {
-        this.listFixedDimensionSize = this.props.estimatedListSize.width;
+        this.listFixedDimensionSize = props.estimatedListSize.width;
       }
     }
   }
 
+  private validateProps() {
+    if (this.props.onRefresh && typeof this.props.refreshing !== "boolean") {
+      throw new CustomError(ExceptionList.refreshBooleanMissing);
+    }
+    if (!(this.props.estimatedItemSize > 0)) {
+      throw new CustomError(ExceptionList.estimatedItemSizeMissing);
+    }
+  }
+
   // Some of the state variables need to update when props change
   static getDerivedStateFromProps<T>(
     nextProps: RecyclerFlatListProps<T>,
diff --git a/src/errors/CustomError.ts b/src/errors/CustomError.ts
new file mode 100644
index 000000000..beb48a6be
--- /dev/null
+++ b/src/errors/CustomError.ts
@@ -0,0 +1,10 @@
+export default class CustomError extends Error {
+  constructor(exception: Exception) {
+    super(exception.type + ": " + exception.message);
+    this.name = exception.type;
+  }
+}
+export interface Exception {
+  type: string;
+  message: string;
+}
diff --git a/src/errors/ExceptionList.ts b/src/errors/ExceptionList.ts
new file mode 100644
index 000000000..1afd26258
--- /dev/null
+++ b/src/errors/ExceptionList.ts
@@ -0,0 +1,15 @@
+import { Exception } from "./CustomError";
+
+const ExceptionList: { [key: string]: Exception } = {
+  estimatedItemSizeMissing: {
+    message:
+      "`estimatedItemSize` is a required prop in RecyclerFlatList. Please provide a value that is greater than 0.",
+    type: "InvalidPropException",
+  },
+  refreshBooleanMissing: {
+    message:
+      "`refreshing` prop must be set as a boolean in order to use `onRefresh`, but got `undefined`",
+    type: "InvariantViolation",
+  },
+};
+export default ExceptionList;

From da33d8b89baf04905d4671077bb7b3fa73a7a2fa Mon Sep 17 00:00:00 2001
From: Talha Naqvi <talha.naqvi@shopify.com>
Date: Wed, 23 Feb 2022 16:00:50 -0800
Subject: [PATCH 2/2] lint fix

---
 src/RecyclerFlatList.tsx  | 1 -
 src/errors/CustomError.ts | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/RecyclerFlatList.tsx b/src/RecyclerFlatList.tsx
index d2c162121..0d1f1b917 100644
--- a/src/RecyclerFlatList.tsx
+++ b/src/RecyclerFlatList.tsx
@@ -13,7 +13,6 @@ import {
   RecyclerListView,
   RecyclerListViewProps,
 } from "recyclerlistview";
-import invariant from "invariant";
 
 import AutoLayoutView, { BlankAreaEventHandler } from "./AutoLayoutView";
 import ItemContainer from "./CellContainer";
diff --git a/src/errors/CustomError.ts b/src/errors/CustomError.ts
index beb48a6be..1d7d2fef4 100644
--- a/src/errors/CustomError.ts
+++ b/src/errors/CustomError.ts
@@ -1,6 +1,6 @@
 export default class CustomError extends Error {
   constructor(exception: Exception) {
-    super(exception.type + ": " + exception.message);
+    super(`${exception.type}: ${exception.message}`);
     this.name = exception.type;
   }
 }