fix(lint): validateStackExpressions reads an object's fields through the guarded reader instead of an inline cast (#15742) (#15791)

* fix(lint): read an object's fields through the guarded reader in buildFieldIndex

`buildFieldIndex` in `validate-expressions.ts` cast every member of an
object's `fields:` list inline (`fields.map(f => (f as AnyRec).name)`).
`Array.isArray` proves the LIST, not its MEMBERS: an empty YAML list item
deserialises to `null`, and the dereference threw out of the whole rule
before the `.filter` two calls later could drop it.

The list is now read through `recordsOf` — the single home of that
coercion — which drops a non-record array member whole and in silence,
the same disposition the two sibling readers in this file
(`buildFieldTypeIndex`, `fieldEntries`) already had. The map shape keeps
`Object.keys`: there the author's key IS the field name.

The sweep's `RESIDUAL_THROWS` rows for `objects[].fields` come out in the
same change — it is exact in both directions, so it now asserts the throw
is gone. `RESIDUAL_INVENTED` is unchanged, measured: the repaired reader
raises no finding about the dropped member.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012zGPuVVX3deAx9LdjK8jCk

* test(lint): keep the #15742 arms in their own top-level describe

They were appended inside the `#15137` assignment-value describe, which
reads as a claim about that suite rather than about `buildFieldIndex`.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012zGPuVVX3deAx9LdjK8jCk

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: claude[bot]

.changeset/lint-validate-expressions-non-record-field-entry.md

@@ -0,0 +1,11 @@
+---
+"@objectstack/lint": patch
+---
+
+`validateStackExpressions` no longer throws on a non-record entry in an object's `fields:` list.
+
+An empty item in a YAML `fields:` list deserialises to `null`, and `buildFieldIndex` cast each member of the list inline (`fields.map(f => (f as AnyRec).name)`) before the `.filter` two calls later could drop it. `Array.isArray` proves the LIST, never its MEMBERS, so linting such a stack failed with `TypeError: Cannot read properties of null (reading 'name')` out of the whole rule instead of reporting anything about the file.
+
+The list is now read through `recordsOf` — the one place that coercion is decided — which drops a non-record member of the array shape whole and in **silence**: it carries no author-written name, so there is nothing to report about it. That matches what the two sibling field readers in the same module (`buildFieldTypeIndex`, `fieldEntries`) already did with the same member, so the three readers now agree. The readable siblings of the junk member are still indexed, so unknown-field findings on that object continue to be reported.
+
+The map shape (`fields: { amount: { … } }`) is unchanged: there the author's key is the field name, which is what this index needs.

packages/lint/src/non-record-object-entry.test.ts

@@ -340,22 +340,22 @@ const SWEPT_COLLECTIONS: readonly SweptCollection[] = [
  * "nothing throws" would have had to be deleted or weakened on the day it was
  * written, and would then never have caught the next one.
  *
- * Every entry names a reader OUTSIDE what #15636 could touch:
+ * It is EMPTY today, and that is a measurement, not an aspiration: no rule in
+ * the table throws on a non-record member of any collection swept here. Two
+ * rows have come out since it was written, each because the sweep went red
+ * demanding a throw that no longer happens — which is the both-directions half
+ * earning its keep, since neither removal started with anyone going looking:
  *
- *  - `objects[].fields` — `buildFieldIndex` in `validate-expressions.ts:137`,
- *    which casts inline instead of through a helper, so the `asArray` sweeps
- *    that produced #15552 and #15636 never saw it. Filed as #15742.
- *
- * `stack.datasets` was here too, for `indexDatasets` in
- * `validate-chart-bindings.ts`. #15741 re-pointed that reader and these
- * assertions went red demanding a throw that no longer happens, which is the
- * both-directions half earning its keep: the rows came out because the sweep
- * failed, not because anyone went looking for them.
+ *  - `stack.datasets` — `indexDatasets` in `validate-chart-bindings.ts`,
+ *    re-pointed by #15741.
+ *  - `objects[].fields` — `buildFieldIndex` in `validate-expressions.ts`, which
+ *    cast each member inline instead of reading through a helper, so the
+ *    `asArray` greps that produced #15552 and #15636 never saw it. It now reads
+ *    the list through `recordsOf` (#15742), which drops a non-record member of
+ *    the array shape whole and in silence, exactly as the file's two sibling
+ *    field readers already did.
  */
-const RESIDUAL_THROWS: Readonly<Record<string, readonly string[]>> = {
-  'objects[].fields · null': ['validateStackExpressions'],
-  'objects[].fields · undefined': ['validateStackExpressions'],
-};
+const RESIDUAL_THROWS: Readonly<Record<string, readonly string[]>> = {};
 
 /**
  * Where a junk member still draws a finding no author's file justifies — the

packages/lint/src/validate-expressions.test.ts

@@ -3931,3 +3931,42 @@ describe('structural condition shape (#15662)', () => {
     });
   });
 });
+
+describe("validateStackExpressions — a non-record entry in an object's `fields:` list (#15742)", () => {
+  // `buildFieldIndex` used to cast each member inline
+  // (`fields.map(f => (f as AnyRec).name)`), so an empty YAML list item —
+  // which deserialises to `null` — threw `Cannot read properties of null`
+  // out of the whole rule. It reads the list through `recordsOf` now, which
+  // is the one place that decision is made: an array member that is not a
+  // record carries no author-written name, so it is dropped WHOLE and in
+  // silence, the same disposition the file's two sibling field readers
+  // (`buildFieldTypeIndex`, `fieldEntries`) already had. The sweep in
+  // `non-record-object-entry.test.ts` pins the absence of the throw across
+  // every rule; these two arms pin what this rule does INSTEAD, which a
+  // crash-only sweep cannot say.
+  const stackWith = (fields: unknown[], condition: string): Record<string, unknown> => ({
+    objects: [{ name: 'crm_account', fields }],
+    flows: [{
+      name: 'account_flow',
+      nodes: [
+        { id: 'start', type: 'start', config: { objectName: 'crm_account' } },
+        { id: 'check', type: 'decision', config: { condition } },
+      ],
+      edges: [],
+    }],
+  });
+
+  it('is dropped in silence rather than thrown on, and invents no finding', () => {
+    expect(validateStackExpressions(stackWith([null, { name: 'amount', type: 'number' }], 'record.amount > 0'))).toHaveLength(0);
+    expect(validateStackExpressions(stackWith([undefined, { name: 'amount', type: 'number' }], 'record.amount > 0'))).toHaveLength(0);
+  });
+
+  it('still indexes the readable siblings — the junk member does not blank the index', () => {
+    // The failure mode a bare `try/catch` repair would have produced: no
+    // crash, and no field knowledge either, so every unknown-field finding
+    // on the object silently stops being reported.
+    const issues = validateStackExpressions(stackWith([null, { name: 'amount', type: 'number' }], 'record.amont > 0'));
+    expect(issues).toHaveLength(1);
+    expect(issues[0].message).toContain('amount');
+  });
+});

packages/lint/src/validate-expressions.ts

@@ -139,7 +139,17 @@ function buildFieldIndex(objects: AnyRec[]): Map<string, string[]> {
     if (!name) continue;
     const fields = obj.fields;
     let names: string[] = [];
-    if (Array.isArray(fields)) names = fields.map(f => (f as AnyRec).name).filter((n): n is string => typeof n === 'string');
+    // The LIST shape is read through `recordsOf` (#15742). `Array.isArray`
+    // proves the list, never its members: an empty item in a YAML `fields:`
+    // list deserialises to `null`, and the cast this replaced dereferenced it
+    // before the `.filter` two calls later could drop it. The two sibling
+    // readers below already guard (`buildFieldTypeIndex` reads `(f)?.name`,
+    // `fieldEntries` filters before mapping) and both drop such a member in
+    // SILENCE — it carries no author-written name, so there is nothing to
+    // report about it — which is what `recordsOf` does for the array shape too.
+    // The MAP shape keeps `Object.keys`: there the author's KEY is the field
+    // name, which is exactly what this "did you mean?" index needs.
+    if (Array.isArray(fields)) names = recordsOf(fields).map(f => f.name).filter((n): n is string => typeof n === 'string');
     else if (fields && typeof fields === 'object') names = Object.keys(fields as AnyRec);
     // Injected columns come second, de-duplicated by insertion order: a DECLARED
     // `owner_id` is the author's field (the registry lets it win), so the