Move checkBlockCounts into BaseSequenceBlock as a general blockCountChanged callback

The call to checkBlockCounts from duplicateBlock can be removed outright, as it already gets called via the call to insert.

client/src/components/StreamField/blocks/BaseSequenceBlock.js

@@ -332,6 +332,8 @@ export class BaseSequenceBlock {
         }
       )
     ];
+
+    this.blockCountChanged();
   }
 
   _onRequestInsert(index, opts) {
@@ -342,6 +344,10 @@ export class BaseSequenceBlock {
     newChild.focus({ soft: true });
   }
 
+  blockCountChanged() {
+    /* Called whenever the block count has changed; subclasses can override this to apply
+    checks on max block count and disable insert / duplicate controls accordingly */
+  }
 
   _insert(childBlockDef, initialState, id, index, opts) {
     const prefix = this.prefix + '-' + this.blockCounter;
@@ -408,6 +414,8 @@ export class BaseSequenceBlock {
       }
     }
 
+    this.blockCountChanged();
+
     return child;
   }
 
@@ -435,6 +443,8 @@ export class BaseSequenceBlock {
       /* we have removed the last child; the new last child cannot be moved down */
       this.children[this.children.length - 1].disableMoveDown();
     }
+
+    this.blockCountChanged();
   }
 
   moveBlock(oldIndex, newIndex) {

client/src/components/StreamField/blocks/StreamBlock.js

@@ -221,7 +221,8 @@ export class StreamBlock extends BaseSequenceBlock {
    *
    * Updates the state of add / duplicate block buttons to prevent too many blocks being inserted.
    */
-  checkBlockCounts() {
+  blockCountChanged() {
+    super.blockCountChanged();
     this.canAddBlock = true;
 
     if (typeof this.blockDef.meta.maxNum === 'number' && this.children.length >= this.blockDef.meta.maxNum) {
@@ -276,12 +277,6 @@ export class StreamBlock extends BaseSequenceBlock {
     return this._insert(childBlockDef, value, id, index, opts);
   }
 
-  _insert(childBlockDef, value, id, index, opts) {
-    const result = super._insert(childBlockDef, value, id, index, opts);
-    this.checkBlockCounts();
-    return result;
-  }
-
   _getChildDataForInsertion({ type }) {
     /* Called when an 'insert new block' action is triggered: given a dict of data from the insertion control,
     return the block definition and initial state to be used for the new block.
@@ -292,11 +287,6 @@ export class StreamBlock extends BaseSequenceBlock {
     return [blockDef, initialState, uuidv4()];
   }
 
-  clear() {
-    super.clear();
-    this.checkBlockCounts();
-  }
-
   duplicateBlock(index, opts) {
     const child = this.children[index];
     const childState = child.getState();
@@ -305,13 +295,6 @@ export class StreamBlock extends BaseSequenceBlock {
     this.insert(childState, index + 1, { animate, collapsed: child.collapsed });
     // focus the newly added field if we can do so without obtrusive UI behaviour
     this.children[index + 1].focus({ soft: true });
-
-    this.checkBlockCounts();
-  }
-
-  deleteBlock(index, opts) {
-    super.deleteBlock(index, opts);
-    this.checkBlockCounts();
   }
 
   setState(values) {