Chart builder: drop unparseable expressions mid-edit, polite glyphed inline feedback

docs/architecture/10-interaction-and-feedback.md

@@ -368,6 +368,19 @@ bullet is the contract; cite it, not the source.)_
 other shows the text visually with no live role. Two live regions would announce the same
 message twice.
 
+**Resolved — inline _live_ validation feedback is polite, glyphed, and field-linked.** A
+validator that re-checks on **every keystroke** (the Chart Builder expression inputs — a
+calculated field, a filter in expression mode) is **not** an assertive `alert`: that would
+interrupt on each character (APG _Alert_ "avoid frequent interruptions"; WCAG 2.2.4). It is a
+**polite `role="status"`** line, and severity reads from a **status glyph** (round error /
+triangle warning, arch 09 §5.2) **plus** colour — never colour alone (§3; WCAG 1.4.1), exactly
+like the guidance warnings above it. The owning `<input>` carries `aria-invalid` for the state
+and `aria-describedby` pointing at the message node so the text is available on focus, not only
+when it changes (GOV.UK _error-message_ field association). Contrast the editor's **render**
+error, which is a discrete, post-debounce result and stays the single `alert` of the rule
+above. _(Consulted via /council → WAI-ARIA APG Alert, GOV.UK error-message, NN/g #9. This
+bullet is the contract; cite it, not the source.)_
+
 **Resolved — feature-modal dismissal & initial focus.** A feature modal (Datasets, Chart
 Builder) is a **passive** `dialog-modal`: dismissed by the close
 button, Escape, or a backdrop click (a passive modal carries no in-flight transaction, so

docs/chart-builder-enhancement-scope.md

@@ -25,7 +25,34 @@
 Newest first. The at-a-glance build-order tracker is §4; per-item detail is §3. This log is
 the quick "where are we" — read it first.
 
-- **2026-06-11** — **1C + 1D + 1E shipped (the Data section). Up next: Phase 2 (2A value-or-field channels, then 2B field shelf).**
+- **2026-06-11 (later)** — **Owed debts on the Data section closed. Up next: Phase 2 (2A value-or-field channels, then 2B field shelf).**
+  - **Council pass** on the new error/disclosure copy (the previously-deferred auto-fire
+    surface). Three a11y conformance gaps against `architecture/10` were fixed: the inline
+    expression feedback now carries a **status glyph** (round error / triangle warning), not
+    colour alone (§3, WCAG 1.4.1); the parse error is a **polite `role="status"`**, not a
+    per-keystroke assertive alert (APG Alert / WCAG 2.2.4); and the message is linked to its
+    input via **`aria-describedby`** (GOV.UK error-message). Unknown-field copy clarified to
+    "…— not a column in this dataset." Resolution recorded in `architecture/10` §5.
+  - **Manual/visual pass** run via a headless-Chrome (Playwright) walk-through of the live
+    builder — filter shelf (predicate + `is between`), field↔expression toggle, expression
+    error/unknown-field glyphs (filter _and_ calc inputs), calculated field, data-preview
+    table with type chips, smart-default chart. All surfaces render as intended.
+  - **Bug found + fixed (mid-edit preview resilience).** `filterTransformObject` /
+    `calculateTransformObject` emitted **any non-empty** expression — including a half-typed,
+    unparseable one — so the preview blanked with a raw render error while the user typed.
+    They now **drop a syntactically-invalid expression** like an empty/incomplete entry
+    (guarded by core `validateExpression`), matching `buildTransforms`' own "a config
+    mid-edit still renders" contract; the inline feedback still flags the typo. Pure core,
+    tested (+2 cases). Visually confirmed: an invalid filter/calc now keeps the last-good
+    chart instead of breaking the preview.
+  - **Verified:** `typecheck` + `test` (741 passing) + `eslint` clean.
+  - **Still open (copy judgment, user's call):** the preview's catch-all
+    `"Couldn't render this chart: {raw Vega message}"` puts a diagnostic in the headline
+    (arch 10 says diagnostics go in a disclosure) — correct in the editor, debatable in the
+    builder; and the builder's terse `"Dataset «X» not found."` drops the next-step the
+    contract mandates (near-unreachable in the builder). Both noted, not changed.
+
+- **2026-06-11** — **1C + 1D + 1E shipped (the Data section).**
   - A new **Data section** at the top of the builder's left pane — "here are your rows;
     shape them, then encode them" — emits the spec's top-level `transform` array.
   - **1C · Filters** — a guarded **field + operator + value** predicate shelf. Operators

docs/manual-verification.md

@@ -65,3 +65,15 @@
 
 - [ ] Library search / sort / empty states, the storage monitor, About & Donate
       modals, and the busy indicator all look deliberate and behave per spec.
+
+## Driving these checks headlessly
+
+The eye-checks above can be scripted as a headless walk-through (Playwright with the
+already-installed Chromium browser cache) for repeatable screenshots, alongside a live
+browser.
+
+- **Select by accessible name / role / placeholder, never by CSS class.** CSS-module class
+  names are content-hashed and unstable; the component tests select the same way.
+- **Reaching the Chart Builder:** open Datasets from the **header command button** (the
+  pane-toggle-strip `Datasets` button only exists once the workspace has content) → **New
+  Dataset** → paste rows inline → **Build Chart**.

docs/spec/06-chart-builder.md

@@ -35,7 +35,7 @@ The section is ordered **input → shaping** so the distinction reads at a glanc
   - The **field** dropdown offers the dataset's columns plus any calculated fields.
   - The **operators** offered depend on the field's type: a measure or temporal field offers `is` / `is not` / `<` / `≤` / `>` / `≥` / `is between` (two bounds); a category offers `is` / `is not` / `is one of` (a comma-separated membership list). A quantitative value compares as a number; other types compare as text (ISO dates sort correctly as text).
 - A filter can be switched to an **expression** power-mode — a raw Vega predicate expression (e.g. `datum.value > 0`) — for what the guarded shelf can't say. The toggle is reversible.
-- An **incomplete** filter (no value yet, a blank range bound, an empty expression) is ignored, so the live preview keeps rendering while the user types.
+- An **incomplete** filter (no value yet, a blank range bound, an empty or syntactically-invalid expression) is ignored, so the live preview keeps rendering while the user types.
 
 ### Calculated fields
 
@@ -47,6 +47,7 @@ The section is ordered **input → shaping** so the distinction reads at a glanc
 
 - Both expression inputs (a filter's expression mode, a calculated field) are validated with **Vega's own expression parser** — the same one the chart uses — so a syntax error is reported **inline** the moment it appears, matching exactly what the chart would accept.
 - A `datum.<field>` reference that does not match a known column raises a soft **"unknown field"** warning (a typo guard) without blocking — the value is genuinely valid Vega, it just won't resolve.
+- An expression that does not parse is **left out of the produced spec** (like an incomplete filter or an unnamed calculated field): the inline error is the only feedback, and a half-typed expression never reaches the renderer — the preview keeps showing the last valid chart.
 
 ## Inputs and Controls