Improve history types, handling unknown category

app/src/frontend/building/edit-history/building-edit-summary.tsx

@@ -3,7 +3,7 @@ import { Link } from 'react-router-dom';
 
 import './building-edit-summary.css';
 
-import { dataFields } from '../../data_fields';
+import { Category, DataFieldDefinition, dataFields } from '../../data_fields';
 import { arrayToDictionary, parseDate } from '../../helpers';
 import { EditHistoryEntry } from '../../models/edit-history-entry';
 
@@ -26,22 +26,26 @@ function formatDate(dt: Date) {
     });
 }
 
+function enrichHistoryEntries(forwardPatch: object, reversePatch: object) {
+    return Object
+        .entries(forwardPatch)
+        .map(([key, value]) => {
+            const info = dataFields[key] as DataFieldDefinition;
+            return {
+                title: info.title || `Unknown field (${key})`,
+                category: info.category || Category.Unknown,
+                value: value,
+                oldValue: reversePatch && reversePatch[key]
+            };
+        });
+}
+
 const BuildingEditSummary: React.FunctionComponent<BuildingEditSummaryProps> = ({
     historyEntry,
     showBuildingId = false,
     hyperlinkCategories = false
 }) => {
-    const entriesWithMetadata = Object
-            .entries(historyEntry.forward_patch)
-            .map(([key, value]) => {
-                const info = dataFields[key] || {};
-                return {
-                    title: info.title || `Unknown field (${key})`,
-                    category: info.category || 'Unknown',
-                    value: value,
-                    oldValue: historyEntry.reverse_patch && historyEntry.reverse_patch[key]
-                };
-            });
+    const entriesWithMetadata = enrichHistoryEntries(historyEntry.forward_patch, historyEntry.reverse_patch);
     const entriesByCategory = arrayToDictionary(entriesWithMetadata, x => x.category);
 
     const categoryHyperlinkTemplate = hyperlinkCategories && historyEntry.building_id != undefined ?
@@ -61,7 +65,7 @@ const BuildingEditSummary: React.FunctionComponent<BuildingEditSummaryProps> = (
             {
                 Object.entries(entriesByCategory).map(([category, fields]) => 
                     <CategoryEditSummary
-                        category={category}
+                        category={category as keyof typeof Category} // https://github.com/microsoft/TypeScript/issues/14106
                         fields={fields}
                         hyperlinkCategory={hyperlinkCategories}
                         hyperlinkTemplate={categoryHyperlinkTemplate}

app/src/frontend/building/edit-history/category-edit-summary.tsx

@@ -8,7 +8,7 @@ import { categories, Category } from '../../data_fields';
 import { FieldEditSummary } from './field-edit-summary';
 
 interface CategoryEditSummaryProps {
-    category: string;
+    category: keyof typeof Category; // https://github.com/microsoft/TypeScript/issues/14106
     fields: {
         title: string;
         value: any;
@@ -19,9 +19,7 @@ interface CategoryEditSummaryProps {
 }
 
 const CategoryEditSummary : React.FunctionComponent<CategoryEditSummaryProps> = props => {
-    const category: Category = Category[props.category];
-    console.log(category);
-    console.log(typeof(category));
+    const category = Category[props.category];
     const categoryInfo = categories[category] || {name: undefined, slug: undefined};
     const categoryName = categoryInfo.name || 'Unknown category';
     const categorySlug = categoryInfo.slug || 'categories';

app/src/frontend/data_fields.ts

@@ -11,6 +11,8 @@ export enum Category {
     Community = 'Community',
     Planning = 'Planning',
     Like = 'Like',
+
+    Unknown = 'Unknown'
 }
 
 export const categories = {
@@ -79,6 +81,18 @@ export const categoriesOrder: Category[] = [
     Category.Like,
 ];
 
+/**
+ * This interface is used only in code which uses dataFields, not in the dataFields definition itself
+ * Cannot make dataFields an indexed type ({[key: string]: DataFieldDefinition}),
+ * because then we wouldn't have type-checking for whether a given key exists on dataFields,
+ * e.g. dataFields.foo_bar would not be highlighted as an error.
+ */
+export interface DataFieldDefinition {
+    category: Category;
+    title: string;
+    tooltip?: string;
+}
+
 export const dataFields = {
     location_name: {
         category: Category.Location,