get rid of a bunch of cheating the typescript strict null checker in …

…jupyter typescript

src/smc-webapp/jupyter/cell-list.tsx

@@ -142,11 +142,14 @@ export class CellList extends Component<CellListProps> {
   } // reset scroll request state
 
   scroll_cell_list = (scroll: any) => {
-    const elt = $(this.cell_list_ref)!;
+    const elt = $(this.cell_list_ref);
+    if (elt == null) {
+      return;
+    }
     if (elt.length > 0) {
       let cur, top;
       if (typeof scroll === "number") {
-        elt.scrollTop(elt.scrollTop()! + scroll);
+        elt.scrollTop(elt.scrollTop() + scroll);
         return;
       }
 
@@ -158,7 +161,7 @@ export class CellList extends Component<CellListProps> {
           top = cur.position().top - elt.position().top;
           if (top < PADDING) {
             scroll = "cell top";
-          } else if (top > elt.height()! - PADDING) {
+          } else if (top > elt.height() - PADDING) {
             scroll = "cell bottom";
           } else {
             return;
@@ -168,37 +171,37 @@ export class CellList extends Component<CellListProps> {
       switch (scroll) {
         case "list up":
           // move scroll position of list up one page
-          return elt.scrollTop(elt.scrollTop()! - elt.height()! * 0.9);
+          return elt.scrollTop(elt.scrollTop() - elt.height() * 0.9);
         case "list down":
           // move scroll position of list up one page
-          return elt.scrollTop(elt.scrollTop()! + elt.height()! * 0.9);
+          return elt.scrollTop(elt.scrollTop() + elt.height() * 0.9);
         case "cell top":
-          cur = elt.find(`#${this.props.cur_id}`)!;
-          if (cur.length > 0) {
+          cur = elt.find(`#${this.props.cur_id}`);
+          if (cur != null && cur.length > 0) {
             return elt.scrollTop(
-              elt.scrollTop()! +
+              elt.scrollTop() +
                 (cur.position().top - elt.position().top) -
                 PADDING
             );
           }
           break;
         case "cell center":
-          cur = elt.find(`#${this.props.cur_id}`)!;
-          if (cur.length > 0) {
+          cur = elt.find(`#${this.props.cur_id}`);
+          if (cur != null && cur.length > 0) {
             return elt.scrollTop(
-              elt.scrollTop()! +
-                (cur.position()!.top - elt.position()!.top) -
-                elt.height()! * 0.5
+              elt.scrollTop() +
+                (cur.position().top - elt.position().top) -
+                elt.height() * 0.5
             );
           }
           break;
         case "cell bottom":
           cur = elt.find(`#${this.props.cur_id}`);
           if (cur.length > 0) {
             return elt.scrollTop(
-              elt.scrollTop()! +
+              elt.scrollTop() +
                 (cur.position().top - elt.position().top) -
-                elt.height()! * 0.9 +
+                elt.height() * 0.9 +
                 PADDING
             );
           }

src/smc-webapp/jupyter/nbconvert.tsx

@@ -40,9 +40,10 @@ class Error extends Component<ErrorProps> {
 
   componentWillReceiveProps(nextProps) {
     if (
-      // TODO: is nbconvert suppose to exist here?
-      !misc.is_string(this.props.nbconvert!.get("error")) &&
-      misc.is_string(nextProps.nbconvert!.get("error"))
+      this.props.nbconvert != null &&
+      !misc.is_string(this.props.nbconvert.get("error")) &&
+      nextProps.nbconvert != null &&
+      misc.is_string(nextProps.nbconvert.get("error"))
     ) {
       setTimeout(() => this.scroll(), 10);
     }
@@ -129,10 +130,10 @@ export class NBConvert extends Component<NBConvertProps> {
   }
 
   render_download() {
-    if (this.props.nbconvert!.get("error")) {
+    if (this.props.nbconvert == null || this.props.nbconvert.get("error") || this.props.nbconvert_dialog == null) {
       return;
     }
-    const to = this.props.nbconvert_dialog!.get("to");
+    const to = this.props.nbconvert_dialog.get("to");
     const info = NAMES[to];
     if (info == null) {
       return;
@@ -275,7 +276,10 @@ export class NBConvert extends Component<NBConvertProps> {
   }
 
   args = () => {
-    return ["--to", this.props.nbconvert_dialog!.get("to")]; // TODO: is this.props.nbconvert_dialog defined?
+    if (this.props.nbconvert_dialog == null) {
+      return []; // broken case -- shouldn't happen
+    }
+    return ["--to", this.props.nbconvert_dialog.get("to")];
   };
 
   run = () => {

src/smc-webapp/jupyter/top-buttonbar.tsx

@@ -194,7 +194,7 @@ export class TopButtonbar0 extends Component<TopButtonbarProps> {
 
   render_select_cell_type() {
     let cell_type: any;
-    if (this.props.sel_ids != null ? this.props.sel_ids!.size > 1 : false) {
+    if (this.props.sel_ids != null ? this.props.sel_ids.size > 1 : false) {
       cell_type = "multi";
     } else {
       cell_type =

src/smc-webapp/jupyter/uncommitted-changes.tsx

@@ -16,7 +16,7 @@ const STYLE: React.CSSProperties = {
 
 interface UncommittedChangesProps {
   has_uncommitted_changes?: boolean;
-  delay_ms?: number; // assumed not to change, default 5000
+  delay_ms: number; // assumed not to change, default 5000
 }
 
 interface UncommittedChangesState {
@@ -54,7 +54,7 @@ export class UncommittedChanges extends Component<
       this._last_change = new Date();
     }
     if (new_props.has_uncommitted_changes) {
-      setTimeout(this._check, this.props.delay_ms! + 10);
+      setTimeout(this._check, this.props.delay_ms + 10);
     }
   }
   componentWillUnmount() {
@@ -63,7 +63,7 @@ export class UncommittedChanges extends Component<
   componentDidMount() {
     this._mounted = true;
     this._last_change = new Date(); // from truly undefined to known
-    setTimeout(this._check, this.props.delay_ms! + 10);
+    setTimeout(this._check, this.props.delay_ms + 10);
   }
   render() {
     if (!this.props.has_uncommitted_changes) {