[Selection auto complete] Suggest "+" after digits. (#28121)

## Summary & Motivation
The only possible continuation after typing digits is a `+` so lets
suggest that.

## How I Tested These Changes

jest + manual testing
<img width="1231" alt="Screenshot 2025-02-28 at 9 22 17 AM"
src="https://github.com/user-attachments/assets/620d767e-f2b9-4223-a73a-ba935faa09af"
/>

js_modules/dagster-ui/packages/ui-core/src/selection/SelectionAutoComplete.g4

@@ -46,7 +46,8 @@ incompleteExpr:
 	| leftParenToken postLogicalOperatorWhitespace expr		# UnclosedParenthesizedExpression
 	| expressionLessParenthesizedExpr						# ExpressionlessParenthesizedExpressionWrapper
 	| leftParenToken postLogicalOperatorWhitespace			# UnclosedExpressionlessParenthesizedExpression
-	| PLUS postNeighborTraversalWhitespace					# IncompletePlusTraversalExpression
+	| DIGITS? PLUS postNeighborTraversalWhitespace			# IncompletePlusTraversalExpression
+	| DIGITS postDigitsWhitespace							# IncompleteUpTraversalExpression
 	| colonToken attributeValue postExpressionWhitespace	# IncompleteAttributeExpressionMissingKey;
 
 expressionLessParenthesizedExpr:
@@ -97,6 +98,8 @@ postUpwardTraversalWhitespace: WS*;
 
 postDownwardTraversalWhitespace: WS*;
 
+postDigitsWhitespace: WS*;
+
 // Value can be a quoted string, unquoted string, or identifier
 value:
 	QUOTED_STRING						# QuotedStringValue

js_modules/dagster-ui/packages/ui-core/src/selection/SelectionAutoCompleteVisitor.ts

@@ -17,8 +17,10 @@ import {
   FunctionNameContext,
   IncompleteAttributeExpressionMissingValueContext,
   IncompletePlusTraversalExpressionContext,
+  IncompleteUpTraversalExpressionContext,
   LeftParenTokenContext,
   OrTokenContext,
+  PostDigitsWhitespaceContext,
   PostDownwardTraversalWhitespaceContext,
   PostLogicalOperatorWhitespaceContext,
   PostNeighborTraversalWhitespaceContext,
@@ -30,7 +32,6 @@ import {
 
 const DEFAULT_TEXT_CALLBACK = (value: string) => value;
 
-// set to true for debug output if desired
 const DEBUG = false;
 
 export class SelectionAutoCompleteVisitor extends BaseSelectionVisitor {
@@ -43,7 +44,6 @@ export class SelectionAutoCompleteVisitor extends BaseSelectionVisitor {
 
   public list: Array<Suggestion> = [];
 
-  // Replacement indices from the original code
   public _startReplacementIndex: number;
   public _stopReplacementIndex: number;
 
@@ -78,7 +78,6 @@ export class SelectionAutoCompleteVisitor extends BaseSelectionVisitor {
     this._stopReplacementIndex = cursorIndex;
   }
 
-  // Keep the same accessors and logging as before
   set startReplacementIndex(newValue: number) {
     if (DEBUG) {
       console.log('Autocomplete suggestions being set by stack:', new Error());
@@ -255,6 +254,12 @@ export class SelectionAutoCompleteVisitor extends BaseSelectionVisitor {
     }
   }
 
+  public visitIncompleteUpTraversalExpression(_ctx: IncompleteUpTraversalExpressionContext) {
+    this.list.push(
+      this.createOperatorSuggestion({text: '+', type: 'up-traversal', displayText: '+'}),
+    );
+  }
+
   public visitIncompletePlusTraversalExpression(ctx: IncompletePlusTraversalExpressionContext) {
     if (
       this.nodeIncludesCursor(ctx.postNeighborTraversalWhitespace()) &&
@@ -306,6 +311,18 @@ export class SelectionAutoCompleteVisitor extends BaseSelectionVisitor {
     }
   }
 
+  public visitPostDigitsWhitespace(ctx: PostDigitsWhitespaceContext) {
+    this.startReplacementIndex = ctx.start.startIndex;
+    this.stopReplacementIndex = ctx.stop!.stopIndex;
+    this.list.push(
+      this.createOperatorSuggestion({
+        text: '+',
+        type: 'up-traversal',
+        displayText: '+',
+      }),
+    );
+  }
+
   public visitPostLogicalOperatorWhitespace(ctx: PostLogicalOperatorWhitespaceContext) {
     if (!this.list.length) {
       const isAfterNot = this.line.slice(0, this.cursorIndex).trim().toLowerCase().endsWith('not');

js_modules/dagster-ui/packages/ui-core/src/selection/SelectionInputHighlighter.ts

@@ -44,7 +44,7 @@ export class SyntaxHighlightingVisitor
 
   private addClass(ctx: ParserRuleContext, klass: string) {
     const from = this.cm.posFromIndex(this.startOffset + ctx.start.startIndex);
-    const to = this.cm.posFromIndex(this.startOffset + ctx.stop!.stopIndex + 1);
+    const to = this.cm.posFromIndex(from.ch + ctx.text.length);
     this.cm.markText(from, to, {className: klass});
   }
 

js_modules/dagster-ui/packages/ui-core/src/selection/__tests__/SelectionAutoComplete.test.ts

@@ -1065,4 +1065,12 @@ describe('createAssetSelectionHint', () => {
       to: 12,
     });
   });
+
+  it('suggests + after digits', () => {
+    expect(testAutocomplete('1234|')).toEqual({
+      from: 4,
+      list: [expect.objectContaining({text: '+'})],
+      to: 4,
+    });
+  });
 });