Guard against decorations being set on update but without changes

Author: grdowns

Extension/src/LanguageServer/client.ts

@@ -654,12 +654,15 @@ class DefaultClient implements Client {
         // Recycle the active text decorations when we receive a new set of inactive regions
         let valuePair: DecorationRangesPair = this.inactiveRegionsDecorations.get(params.uri);
         if (valuePair) {
-            // Disposing of and resetting the decoration will undo previously applied text decorations
-            valuePair.decoration.dispose();
-            valuePair.decoration = decoration;
-
-            // As vscode.TextEditor.setDecorations only applies to visible editors, we must cache the range for when another editor becomes visible
-            valuePair.ranges = params.ranges;
+            // The language server will send notifications regardless of whether the ranges have changed. Unfortunately we must check for changes ourselves
+            if (this.isRangesEqual(valuePair.ranges, params.ranges)) {
+                // Disposing of and resetting the decoration will undo previously applied text decorations
+                valuePair.decoration.dispose();
+                valuePair.decoration = decoration;
+
+                // As vscode.TextEditor.setDecorations only applies to visible editors, we must cache the range for when another editor becomes visible
+                valuePair.ranges = params.ranges;
+            }
         } else { // The entry does not exist. Make a new one
             let toInsert: DecorationRangesPair = {
                 decoration: decoration,
@@ -675,6 +678,21 @@ class DefaultClient implements Client {
         }
     }
 
+    // Helper method to compare two ranges for equality
+    private isRangesEqual(r1: vscode.Range[], r2: vscode.Range[]): boolean {
+        if (r1.length !== r2.length) {
+            return false;
+        }
+
+        for (let e1 of r1) {
+            for (let e2 of r2) {
+                if (e1 !== e2) {
+                    return false;
+                }
+            }
+        }
+    }
+
     /*********************************************
      * requests to the language server
      *********************************************/