fix merging snippets

increase nesting level of the snippet based on how many snippets need to be merged instead an arbitrary value of 10 and reorder the indexes afterwards to avoid floating point problems where nestinglevel< 1e-15 would be added upon index > 1, where the index then wouldn't change.

Author: superle3

src/vs/editor/contrib/snippet/browser/snippetSession.ts

@@ -289,7 +289,13 @@ export class OneSnippet {
 	merge(others: OneSnippet[]): void {
 
 		const model = this._editor.getModel();
-		this._nestingLevel *= 10;
+		const nestingLevel = Math.max(8, ...others.map((o, i) => {
+			if (i < this._placeholderGroups[this._placeholderGroupsIdx].length) {
+				return o._snippet.placeholderInfo.last!.index || 8;
+			}
+			return 8;
+		})) + 2;
+		this._nestingLevel *= nestingLevel;
 
 		this._editor.changeDecorations(accessor => {
 
@@ -309,9 +315,9 @@ export class OneSnippet {
 
 				for (const nestedPlaceholder of nested._snippet.placeholderInfo.all) {
 					if (nestedPlaceholder.isFinalTabstop) {
-						nestedPlaceholder.index = placeholder.index + ((indexLastPlaceholder + 1) / this._nestingLevel);
+						nestedPlaceholder.index = placeholder.index + ((indexLastPlaceholder + 1) / nestingLevel);
 					} else {
-						nestedPlaceholder.index = placeholder.index + (nestedPlaceholder.index / this._nestingLevel);
+						nestedPlaceholder.index = placeholder.index + (nestedPlaceholder.index / nestingLevel);
 					}
 				}
 				this._snippet.replace(placeholder, nested._snippet.children);
@@ -339,6 +345,15 @@ export class OneSnippet {
 			// Last, re-create the placeholder groups by sorting placeholders by their index.
 			this._placeholderGroups = groupBy(this._snippet.placeholders, Placeholder.compareByIndex);
 		});
+		// Reorder indexes to only use ints to avoid floating point issues
+		for (const [i, placeholderGroup] of this._placeholderGroups.entries()) {
+			for (const placeholder of placeholderGroup) {
+				if (placeholder.isFinalTabstop) {
+					break;
+				}
+				placeholder.index = i + 1;
+			}
+		}
 	}
 
 	getEnclosingRange(): Range | undefined {