cleanup: UNSAFE_componentWillReceiveProps -> modern lifecycles (React 19)

The 4 class components on UNSAFE_componentWillReceiveProps converted:
- FromNow, FireStats: state is a pure mirror of props -> getDerivedStateFromProps
- Fires: split the derived state (getDerivedStateFromProps) from the URL-
  canonicalization side effect (componentDidUpdate, guarded by prevProps) so
  the side effect never runs inside the pure gDSFP
- SelectionMap: marker is also locally draggable, so gDSFP would clobber a
  drag -> componentDidUpdate guarded on a real center/distance value change
  (no clobber, no setState loop), merged with the existing fit()

Browser-verified: /fires count, fire detail + FromNow, active-fire URL
canonicalizes to /fire/archive/:id, home SelectionMap renders stably (no
render loop). No UNSAFE_ warnings remain from our code. REST smoke
byte-identical.

imports/ui/components/FromNow/FromNow.js

@@ -18,13 +18,9 @@ class FromNow extends Component {
     };
   }
 
-  UNSAFE_componentWillReceiveProps(nextProps) {
-    if (this.props.when !== nextProps.when) {
-      // console.log(`Next when ${nextProps.when}`);
-      this.setState({
-        when: nextProps.when
-      });
-    }
+  // state.when just mirrors props.when (was UNSAFE_componentWillReceiveProps)
+  static getDerivedStateFromProps(props, state) {
+    return props.when !== state.when ? { when: props.when } : null;
   }
 
   shouldComponentUpdate(nextProps, nextState) {
@@ -36,7 +32,6 @@ class FromNow extends Component {
   }
 
   render() {
-    console.log(`Render from now ${this.state.when}`);
     return (
       <span data-toggle="tooltip" className="from-now" title={this.thatIs()}>{this.state.when}</span>
     );
@@ -49,9 +44,6 @@ FromNow.propTypes = {
   whenDate: PropTypes.instanceOf(Date)
 };
 
-FromNow.defaultProps = {
-};
-
 /*
  * const FromNowContainer = withTracker((props) => {
  *

imports/ui/components/SelectionMap/SelectionMap.js

@@ -60,18 +60,22 @@ class SelectionMap extends Component {
     }
   }
 
-  UNSAFE_componentWillReceiveProps(nextProps) {
-    const nextCenter = nextProps.center[0] ? nextProps.center : this.state.center;
-    const nextMarker = nextProps.center[0] ? nextProps.center : this.state.marker;
-    this.setState({
-      center: nextCenter,
-      marker: nextMarker,
-      distance: nextProps.distance || this.state.distance
-    });
-    // this.fit();
-  }
-
-  componentDidUpdate() {
+  // Was UNSAFE_componentWillReceiveProps: pull center/distance from props into
+  // state when they actually change. Done in componentDidUpdate (not
+  // getDerivedStateFromProps) because the marker is also locally draggable, so
+  // we must guard on a real value change to avoid clobbering a drag / looping.
+  componentDidUpdate(prevProps) {
+    const { center, distance } = this.props;
+    const centerChanged = center[0] &&
+      (center[0] !== this.state.center[0] || center[1] !== this.state.center[1]);
+    const distanceChanged = distance && distance !== this.state.distance;
+    if (centerChanged || distanceChanged) {
+      this.setState({
+        center: center[0] ? center : this.state.center,
+        marker: center[0] ? center : this.state.marker,
+        distance: distance || this.state.distance
+      });
+    }
     this.fit();
   }
 

imports/ui/pages/Fires/Fires.js

@@ -37,18 +37,25 @@ class Fire extends React.Component {
     };
   }
 
-  UNSAFE_componentWillReceiveProps(nextProps) {
-    if (this.props.when !== nextProps.when || this.props.loading !== nextProps.loading || this.props.notfound !== nextProps.notfound) {
-      // console.log(`Next when ${nextProps.when}`);
-      if (nextProps.fire && (nextProps.alert || nextProps.active || nextProps.fromHash)) {
-        // change url to archive with new _id
-        nextProps.history.replace(`/fire/archive/${hexId(nextProps.fire._id)}`);
+  // state mirrors props purely for shouldComponentUpdate (render reads props
+  // directly). Was the derived-state half of UNSAFE_componentWillReceiveProps.
+  static getDerivedStateFromProps(props, state) {
+    if (props.when !== state.when || props.loading !== state.loading || props.notfound !== state.notfound) {
+      return { loading: props.loading, notfound: props.notfound, when: props.when };
+    }
+    return null;
+  }
+
+  componentDidUpdate(prevProps) {
+    // side effect (must not run in getDerivedStateFromProps): once the fire is
+    // resolved via alert/active/hash, canonicalize the URL to /fire/archive/:id
+    if (prevProps.when !== this.props.when || prevProps.loading !== this.props.loading || prevProps.notfound !== this.props.notfound) {
+      const {
+        fire, alert, active, fromHash, history
+      } = this.props;
+      if (fire && (alert || active || fromHash)) {
+        history.replace(`/fire/archive/${hexId(fire._id)}`);
       }
-      this.setState({
-        loading: nextProps.loading,
-        notfound: nextProps.notfound,
-        when: nextProps.when
-      });
     }
   }
 

imports/ui/pages/FiresMap/FireStats.js

@@ -17,17 +17,19 @@ class FireStats extends Component {
     };
   }
 
-  UNSAFE_componentWillReceiveProps(nextProps) {
-    if (this.props.lastCheck !== nextProps.lastCheck ||
-        this.props.lastFireDetected !== nextProps.lastFireDetected ||
-        this.props.loadingAll !== nextProps.loadingAll
+  // state mirrors props (was UNSAFE_componentWillReceiveProps)
+  static getDerivedStateFromProps(props, state) {
+    if (props.lastCheck !== state.lastCheck ||
+        props.lastFireDetected !== state.lastFireDetected ||
+        props.loadingAll !== state.loadingAll
     ) {
-      this.setState({
-        lastFireDetected: nextProps.lastFireDetected,
-        lastCheck: nextProps.lastCheck,
-        loadingAll: nextProps.loadingAll
-      });
+      return {
+        lastFireDetected: props.lastFireDetected,
+        lastCheck: props.lastCheck,
+        loadingAll: props.loadingAll
+      };
     }
+    return null;
   }
 
   shouldComponentUpdate(nextProps, nextState) {
@@ -54,7 +56,4 @@ FireStats.propTypes = {
   lastCheck: PropTypes.instanceOf(Date)
 };
 
-FireStats.defaultProps = {
-};
-
 export default withTranslation()(FireStats);