Make more code conform to strict null checks (#10219

* Make more code conform to strict null checks

* Fix types

* Fix tests

* Fix remaining test assertions

* Iterate PR

src/components/views/elements/EditableTextContainer.tsx

@@ -32,7 +32,7 @@ interface IProps {
 
     /* callback to update the value. Called with a single argument: the new
      * value. */
-    onSubmit?: (value: string) => Promise<{} | void>;
+    onSubmit: (value: string) => Promise<{} | void>;
 
     /* should the input submit when focus is lost? */
     blurToSubmit?: boolean;
@@ -40,7 +40,7 @@ interface IProps {
 
 interface IState {
     busy: boolean;
-    errorString: string;
+    errorString: string | null;
     value: string;
 }
 
@@ -72,7 +72,7 @@ export default class EditableTextContainer extends React.Component<IProps, IStat
         this.state = {
             busy: false,
             errorString: null,
-            value: props.initialValue,
+            value: props.initialValue ?? "",
         };
     }
 

src/components/views/elements/SSOButtons.tsx

@@ -113,7 +113,7 @@ const SSOButton: React.FC<ISSOButtonProps> = ({
         brandClass = `mx_SSOButton_brand_${brandName}`;
         icon = <img src={brandIcon} height="24" width="24" alt={brandName} />;
     } else if (typeof idp?.icon === "string" && idp.icon.startsWith("mxc://")) {
-        const src = mediaFromMxc(idp.icon, matrixClient).getSquareThumbnailHttp(24);
+        const src = mediaFromMxc(idp.icon, matrixClient).getSquareThumbnailHttp(24) ?? undefined;
         icon = <img src={src} height="24" width="24" alt={idp.name} />;
     }
 

src/components/views/elements/SearchWarning.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactNode } from "react";
 import { logger } from "matrix-js-sdk/src/logger";
 
 import EventIndexPeg from "../../../indexing/EventIndexPeg";
@@ -31,13 +31,13 @@ export enum WarningKind {
 }
 
 interface IProps {
-    isRoomEncrypted: boolean;
+    isRoomEncrypted?: boolean;
     kind: WarningKind;
 }
 
 export default function SearchWarning({ isRoomEncrypted, kind }: IProps): JSX.Element {
-    if (!isRoomEncrypted) return null;
-    if (EventIndexPeg.get()) return null;
+    if (!isRoomEncrypted) return <></>;
+    if (EventIndexPeg.get()) return <></>;
 
     if (EventIndexPeg.error) {
         return (
@@ -69,8 +69,8 @@ export default function SearchWarning({ isRoomEncrypted, kind }: IProps): JSX.El
     const brand = SdkConfig.get("brand");
     const desktopBuilds = SdkConfig.getObject("desktop_builds");
 
-    let text = null;
-    let logo = null;
+    let text: ReactNode | undefined;
+    let logo: JSX.Element | undefined;
     if (desktopBuilds.get("available")) {
         logo = <img src={desktopBuilds.get("logo")} />;
         const buildUrl = desktopBuilds.get("url");
@@ -116,7 +116,7 @@ export default function SearchWarning({ isRoomEncrypted, kind }: IProps): JSX.El
     // for safety
     if (!text) {
         logger.warn("Unknown desktop builds warning kind: ", kind);
-        return null;
+        return <></>;
     }
 
     return (

src/components/views/elements/Validation.tsx

@@ -26,7 +26,7 @@ interface IResult {
     text: string;
 }
 
-interface IRule<T, D = void> {
+interface IRule<T, D = undefined> {
     key: string;
     final?: boolean;
     skip?(this: T, data: Data, derivedData: D): boolean;
@@ -90,14 +90,12 @@ export default function withValidation<T = void, D = void>({
         { value, focused, allowEmpty = true }: IFieldState,
     ): Promise<IValidationResult> {
         if (!value && allowEmpty) {
-            return {
-                valid: null,
-                feedback: null,
-            };
+            return {};
         }
 
         const data = { value, allowEmpty };
-        const derivedData: D | undefined = deriveData ? await deriveData.call(this, data) : undefined;
+        // We know that if deriveData is set then D will not be undefined
+        const derivedData: D = (await deriveData?.call(this, data)) as D;
 
         const results: IResult[] = [];
         let valid = true;
@@ -149,10 +147,7 @@ export default function withValidation<T = void, D = void>({
 
         // Hide feedback when not focused
         if (!focused) {
-            return {
-                valid,
-                feedback: null,
-            };
+            return { valid };
         }
 
         let details;