fix: Improve auto-complete behavior for aliases and maps (#1987)

## Summary

This PR improves auto-complete in the following ways

1. Auto-complete suggestions will not appear after `AS`, since it is assumed that a user will not want to type an existing column or function name as a column alias
2. Accepting an auto-complete suggestion will replace characters after the cursor if they match the accepted suggestion. This is nice when, for example, I have typed `ResourceAttributes[]` and my cursor is before the `]` - accepting a suggestion will now replace the trailing `]` instead of leaving it be (in which case it would be duplicated after inserting the suggestion).

### Screenshots or video

https://github.com/user-attachments/assets/9577393c-6bfa-410b-b5ba-2ba6b00bc26b

### How to test locally or on Vercel

This can be tested in the preview environment.

### References



- Linear Issue: Closes HDX-2612
- Related PRs:

.changeset/smooth-poems-film.md

@@ -0,0 +1,5 @@
+---
+"@hyperdx/app": patch
+---
+
+fix: Improve auto-complete behavior for aliases and maps

packages/app/src/components/SQLEditor/__tests__/utils.test.ts

@@ -0,0 +1,150 @@
+import { Completion, CompletionContext } from '@codemirror/autocomplete';
+import { EditorState } from '@codemirror/state';
+
+import { createIdentifierCompletionSource } from '../utils';
+
+const TEST_COMPLETIONS: Completion[] = [
+  { label: 'column1', type: 'variable' },
+  { label: 'column2', type: 'variable' },
+  { label: 'SELECT', type: 'keyword' },
+  { label: 'count', type: 'function', apply: 'count(' },
+];
+
+/**
+ * Simulates what CodeMirror shows the user: calls the completion source,
+ * extracts the typed prefix (text from `result.from` to cursor), and
+ * filters options by case-insensitive prefix match on the label.
+ *
+ * Returns the filtered labels, or null when the source suppresses completions.
+ */
+function getSuggestionLabels(
+  doc: string,
+  {
+    pos,
+    explicit = false,
+    completions = TEST_COMPLETIONS,
+  }: { pos?: number; explicit?: boolean; completions?: Completion[] } = {},
+): string[] | null {
+  const source = createIdentifierCompletionSource(completions);
+  const state = EditorState.create({ doc });
+  const cursorPos = pos ?? doc.length;
+  const context = new CompletionContext(state, cursorPos, explicit);
+  const result = source(context);
+
+  if (result == null) return null;
+
+  const typedPrefix = doc.slice(result.from, cursorPos).toLowerCase();
+  return result.options
+    .filter(o => o.label.toLowerCase().startsWith(typedPrefix))
+    .map(o => o.label);
+}
+
+/**
+ * Returns the range [from, to] that CodeMirror would replace when the user
+ * accepts a suggestion. This lets us verify that the entire identifier
+ * (including any trailing characters after the cursor) gets replaced.
+ */
+function getReplacementRange(
+  doc: string,
+  pos: number,
+): { from: number; to: number } | null {
+  const source = createIdentifierCompletionSource(TEST_COMPLETIONS);
+  const state = EditorState.create({ doc });
+  const context = new CompletionContext(state, pos, false);
+  const result = source(context);
+  if (result == null) return null;
+  return { from: result.from, to: result.to ?? pos };
+}
+
+describe('Auto-Complete source', () => {
+  it.each([
+    { doc: 'SELECT col', expected: ['column1', 'column2'] },
+    { doc: 'sel', expected: ['SELECT'] },
+    { doc: 'SELECT xyz', expected: [] },
+    { doc: 'SELECT count(*) AS total, col', expected: ['column1', 'column2'] },
+  ])('suggests matching completions for "$doc"', ({ doc, expected }) => {
+    expect(getSuggestionLabels(doc)).toEqual(expected);
+  });
+
+  it('returns all options when prefix is empty (Ctrl+Space)', () => {
+    const labels = getSuggestionLabels('', { explicit: true });
+    expect(labels).toEqual(['column1', 'column2', 'SELECT', 'count']);
+  });
+
+  it('returns null when there is no prefix and no Ctrl+Space', () => {
+    expect(getSuggestionLabels('')).toBeNull();
+  });
+
+  it.each([
+    {
+      name: 'dots and brackets',
+      doc: "ResourceAttributes['service.name']",
+      completions: [
+        { label: "ResourceAttributes['service.name']", type: 'variable' },
+      ],
+      expected: ["ResourceAttributes['service.name']"],
+    },
+    {
+      name: '$ macros',
+      doc: 'WHERE $__date',
+      completions: [
+        { label: '$__dateFilter', type: 'variable' },
+        { label: 'column1', type: 'variable' },
+      ],
+      expected: ['$__dateFilter'],
+    },
+    {
+      name: 'curly braces and colons',
+      doc: 'WHERE {name:',
+      completions: [
+        { label: '{name:String}', type: 'variable' },
+        { label: 'column1', type: 'variable' },
+      ],
+      expected: ['{name:String}'],
+    },
+  ])('supports identifiers with $name', ({ doc, completions, expected }) => {
+    expect(getSuggestionLabels(doc, { completions })).toEqual(expected);
+  });
+
+  describe('AS keyword suppression', () => {
+    it.each([
+      { name: 'AS (uppercase)', doc: 'SELECT count(*) AS ali' },
+      { name: 'as (lowercase)', doc: 'SELECT count(*) as ali' },
+      { name: 'AS with extra whitespace', doc: 'SELECT count(*) AS   ali' },
+    ])('returns null after $name', ({ doc }) => {
+      expect(getSuggestionLabels(doc)).toBeNull();
+    });
+
+    it('does not suppress when AS is part of a larger word', () => {
+      expect(getSuggestionLabels('SELECT CAST')).toEqual([]);
+    });
+  });
+
+  describe('mid-identifier completion', () => {
+    it.each([
+      {
+        name: "cursor before trailing ']",
+        doc: "ResourceAttributes['host.']",
+        pos: 25, // after 'host.'
+        expectedRange: { from: 0, to: 27 },
+      },
+      {
+        name: 'cursor in middle of a word',
+        doc: 'SELECT column1',
+        pos: 10, // after 'col'
+        expectedRange: { from: 7, to: 14 },
+      },
+      {
+        name: 'cursor at end of identifier (no trailing chars)',
+        doc: 'SELECT column1',
+        pos: 14,
+        expectedRange: { from: 7, to: 14 },
+      },
+    ])(
+      'replacement range covers full identifier when $name',
+      ({ doc, pos, expectedRange }) => {
+        expect(getReplacementRange(doc, pos)).toEqual(expectedRange);
+      },
+    );
+  });
+});

packages/app/src/components/SQLEditor/utils.ts

@@ -19,21 +19,41 @@ export type SQLCompletion = {
   type?: string;
 };
 
+// Characters that form SQL identifiers in our editor: word chars, dots,
+// single quotes, brackets, $, {, }, and : — to support expressions like
+// `ResourceAttributes['service.name']`, `$__dateFilter`, `{name:Type}`.
+const IDENTIFIER_CHAR = "[\\w.'[\\]${}:]";
+const IDENTIFIER_BEFORE = new RegExp(`${IDENTIFIER_CHAR}+`);
+const IDENTIFIER_AFTER = new RegExp(`^${IDENTIFIER_CHAR}+`);
+const IDENTIFIER_VALID_FOR = new RegExp(`^${IDENTIFIER_CHAR}*$`);
+
 /**
  * Creates a custom CodeMirror completion source for SQL identifiers (column names, table
  * names, functions, etc.) that inserts them verbatim, without quoting.
  */
-function createIdentifierCompletionSource(completions: Completion[]) {
+export function createIdentifierCompletionSource(completions: Completion[]) {
   return (context: CompletionContext) => {
-    // Match word characters, dots, single quotes, brackets, $, {, }, and :
-    // to support identifiers like `ResourceAttributes['service.name']`,
-    // macros like `$__dateFilter`, and query params like `{name:Type}`
-    const prefix = context.matchBefore(/[\w.'[\]${}:]+/);
+    const prefix = context.matchBefore(IDENTIFIER_BEFORE);
     if (!prefix && !context.explicit) return null;
+
+    // Suppress suggestions after AS keyword since the user is typing a custom alias
+    const textBefore = context.state.doc
+      .sliceString(0, prefix?.from ?? context.pos)
+      .trimEnd();
+    if (/\bAS$/i.test(textBefore)) return null;
+
+    // Look forward from cursor to include trailing identifier characters
+    // (e.g. the `']` in `ResourceAttributes['host.']`) so accepting a
+    // suggestion replaces the entire identifier, not just up to the cursor.
+    const docText = context.state.doc.sliceString(context.pos);
+    const suffix = docText.match(IDENTIFIER_AFTER);
+    const to = suffix ? context.pos + suffix[0].length : context.pos;
+
     return {
       from: prefix?.from ?? context.pos,
+      to,
       options: completions,
-      validFor: /^[\w.'[\]${}:]*$/,
+      validFor: IDENTIFIER_VALID_FOR,
     };
   };
 }