[ES|QL] Improve PROMQL command params map parsing (elastic#250633)

## Summary

Improves `PROMQL` command parsing:

- Mostly improves params map index pattern parsing. Now the parser
properly breaks down index patterns into their constituent parts
(cluster, index, selector) and wraps them in a new "bare" list AST node
type.
- Added support for a new 'bare' list subtype—lists without any
enclosing brackets.
- The pretty printers (BasicPrettyPrinter and WrappingPrettyPrinter) now
know how to format these correctly, without adding extra brackets or
weird indentation.
- Also added a helper `Builder.expression.list.bare()` for constructing
these nodes programmatically.


### Checklist


- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Author: vadimkibana

src/platform/packages/shared/kbn-esql-language/src/ast/builder/builder.ts

@@ -375,6 +375,21 @@ export namespace Builder {
           name: '',
         };
       };
+
+      export const bare = (
+        template: Omit<AstNodeTemplate<ESQLList>, 'name' | 'values'> &
+          Partial<Pick<ESQLList, 'values'>> = {},
+        fromParser?: Partial<AstNodeParserFields>
+      ): ESQLList => {
+        return {
+          values: [],
+          ...template,
+          ...Builder.parserFields(fromParser),
+          type: 'list',
+          subtype: 'bare',
+          name: '',
+        };
+      };
     }
 
     export namespace literal {

src/platform/packages/shared/kbn-esql-language/src/commands/definitions/utils/promql.ts

@@ -17,7 +17,7 @@ import {
 import { promqlFunctionDefinitions } from '../generated/promql_functions';
 import { buildFunctionDocumentation } from './documentation';
 import { withAutoSuggest } from './autocomplete/helpers';
-import { isIdentifier, isSource } from '../../../ast/is';
+import { isIdentifier, isList, isSource } from '../../../ast/is';
 import { SuggestionCategory } from '../../../shared/sorting';
 import { techPreviewLabel } from './shared';
 
@@ -153,6 +153,21 @@ export function getIndexFromPromQLParams({
 
     const { value } = indexEntry ?? {};
 
+    if (isList(value) && value.values.length > 0) {
+      const listText = value.text?.trim();
+      if (listText) {
+        return listText;
+      }
+
+      const names = value.values
+        .map((item) => (isIdentifier(item) || isSource(item) ? item.name : ''))
+        .filter(Boolean);
+
+      if (names.length > 0) {
+        return names.join(',');
+      }
+    }
+
     if ((isIdentifier(value) || isSource(value)) && !value.name.includes(EDITOR_MARKER)) {
       return value.name;
     }

src/platform/packages/shared/kbn-esql-language/src/commands/registry/promql/columns_after.test.ts

@@ -60,4 +60,25 @@ describe('PROMQL columnsAfter', () => {
 
     expect(result).toEqual([]);
   });
+
+  it('passes multiple indices to fromFrom', async () => {
+    const fromFrom = jest.fn().mockResolvedValue([]);
+
+    await columnsAfter(
+      synth.cmd`PROMQL index=metrics,logs-tsdb rate(http_requests_total[5m])`,
+      [],
+      '',
+      {
+        fromFrom,
+        fromJoin: () => Promise.resolve([]),
+        fromEnrich: () => Promise.resolve([]),
+      }
+    );
+
+    expect(fromFrom).toHaveBeenCalledTimes(1);
+
+    const [cmd] = fromFrom.mock.calls[0];
+    expect(String(cmd)).toContain('metrics');
+    expect(String(cmd)).toContain('logs-tsdb');
+  });
 });

src/platform/packages/shared/kbn-esql-language/src/commands/registry/promql/validate.ts

@@ -10,11 +10,12 @@
 import type {
   ESQLAst,
   ESQLAstAllCommands,
+  ESQLAstExpression,
   ESQLAstPromqlCommand,
   ESQLLocation,
   ESQLMessage,
 } from '../../../types';
-import { isIdentifier } from '../../../ast/is';
+import { isIdentifier, isList, isSource } from '../../../ast/is';
 import type { ICommandContext } from '../types';
 import { getMessageFromId } from '../../definitions/utils';
 import { sourceExists } from '../../definitions/utils/sources';
@@ -219,7 +220,7 @@ function collectPromqlParamValues(
         continue;
       }
 
-      const rawValue = entry.value.text?.trim() ?? '';
+      const rawValue = getPromqlParamValueText(entry.value);
       const value = looksLikePromqlParamAssignment(rawValue) ? '' : rawValue;
 
       values.set(key, {
@@ -245,6 +246,24 @@ function collectPromqlParamValues(
   return values;
 }
 
+function getPromqlParamValueText(value: ESQLAstExpression | undefined): string {
+  if (!value) return '';
+
+  const text = value.text?.trim();
+  if (text) return text;
+
+  if (isList(value)) {
+    const parts = value.values
+      .map((item) => item.text?.trim() || (isIdentifier(item) || isSource(item) ? item.name : ''))
+      .filter(Boolean);
+
+    return parts.join(',');
+  }
+
+  if (isIdentifier(value) || isSource(value)) return value.name;
+
+  return '';
+}
 /*
  * Extracts the PromQL query text from the AST.
  *
@@ -314,7 +333,7 @@ function getPromqlQueryTail(command: ESQLAstPromqlCommand): string {
         continue;
       }
 
-      const rawValue = entry.value.text ?? '';
+      const rawValue = getPromqlParamValueText(entry.value);
       const keyPrefix = `${key}=`;
       const valuePrefix = `${keyPrefix}${rawValue}`;
       const lowerRest = rest.toLowerCase();