Adding a Table Column Type

A column type is one file in apps/sim/lib/table/column-types/ plus a registry entry. Everything that varies per type — label, icon, storage cast, coercion, validation, conversion compatibility, formatting, editor, filter operators — lives on that one object, so no consumer needs editing.

This was not always true: adding currency originally took ~40 edits across 32 switch arms and 26 UI branches, each of which failed silently when missed. The registry exists to make that impossible, so the rule is absolute: if you find yourself adding a case 'yourtype': anywhere outside column-types/, the registry is missing a field. Add the field instead.

Hard Rule: the compiler tells you what to do

Do not hunt for places to edit. Add your type to the ColumnType union first and let tsc produce the list:

cd apps/sim && bun run type-check

You will get two errors, naming column-types/registry.ts and column-types/registry.server.ts. Register in both.

If your type owns metadata, adding its key to TYPE_SPECIFIC_COLUMN_KEYS produces two more legitimate errors — FOREIGN_METADATA_VERB in validation.ts (a Record over those keys) and the key's absence from ColumnDefinition. Those are the gate working, not sites to "fix".

Any error beyond those four is a site reading a hardcoded type list that should read the registry — fix that site, don't work around it.

Directory Structure

apps/sim/lib/table/column-types/
├── types.ts             # ColumnTypeDefinition — the contract you implement
├── types.server.ts      # ColumnTypeServerDefinition — cell migrations only
├── registry.ts          # Record<ColumnType, …>  ← client-safe, the gate
├── registry.server.ts   # Record<ColumnType, …>  ← adds migrations (drizzle)
├── index.ts             # barrel + accessors (columnTypeOf, columnTypeById, …)
└── {type}.ts            # one file per type — what you write

Step 1: Pick the storage shape

Decide what a cell literally holds in user_table_rows.data (JSONB). This drives almost everything else:

Prefer an existing primitive over a new shape. currency stores a plain number and keeps its ISO code as display metadata — which is why filtering, sorting, uniqueness, and CSV export all reuse the numeric paths untouched, and why re-denominating a column rewrites zero rows.

Step 2: Add the icon

Create packages/emcn/src/icons/type-{name}.tsx, copying the geometry conventions of its siblings exactly:

import type { SVGProps } from 'react'

/**
 * Type {name} icon component - {what the glyph is} for {name} columns
 * @param props - SVG properties including className, fill, etc.
 */
export function Type{Pascal}(props: SVGProps<SVGSVGElement>) {
  return (
    <svg
      width='24'
      height='24'
      viewBox='-1.75 -1.5 24 24'
      fill='none'
      stroke='currentColor'
      strokeWidth='1.55'
      strokeLinecap='round'
      strokeLinejoin='round'
      xmlns='http://www.w3.org/2000/svg'
      aria-hidden='true'
      {...props}
    >
      <path d='…' />
    </svg>
  )
}

• viewBox='-1.75 -1.5 24 24' is the type-* family value, not the set-wide default. Match the family.
• Center the glyph on the viewBox's optical center (y = 10.5, x = 10.25) — every sibling does, and a few tenths off is visible at size-[14px].
• Export alphabetically by component name in packages/emcn/src/icons/index.ts.

Step 3: Write the type file

apps/sim/lib/table/column-types/{name}.ts. Copy the closest existing type and change what differs. Every field is required by the interface, so the compiler enumerates them for you — read the TSDoc in types.ts rather than guessing.

The three that are easy to get wrong:

• coerce is the single write-path implementation. The server runs it before persisting and the grid runs it to fill the optimistic cache. Accept every shape the value legitimately arrives in (paste, CSV, tool write), because rejecting means the cell is nulled.
• isCompatibleWith gates type conversion and must read the value exactly as coerce will, or a conversion will pass its check and then null the cell.
• ownedMetadata lists the ColumnDefinition keys your type owns. Anything you add must also be added to TYPE_SPECIFIC_COLUMN_KEYS in types.ts and given a phrase in FOREIGN_METADATA_VERB in validation.ts — both are Record-typed, so the compiler will tell you.

Step 4: Register

Add the entry to COLUMN_TYPE_REGISTRY in registry.ts and COLUMN_TYPE_SERVER_REGISTRY in registry.server.ts.

COLUMN_TYPES is declared in types.ts (not derived from the registry — the registry is annotated Record<ColumnType, …> against it, which is the gate). constants.ts re-exports it, so columnTypeSchema = z.enum(COLUMN_TYPES) picks your type up with no edit. Type-specific metadata does not — see the next step.

Step 5: Migrations (only if the stored bytes change)

If converting an existing column to your type must rewrite cells, add migrateCellsTo in registry.server.ts; if converting away must rewrite them, add migrateCellsFrom.

This is load-bearing, not cosmetic: filters and sorts apply jsonbCast to whatever is stored, so leaving a non-castable string behind makes every query on that column fail — not merely render oddly.

Prefer set-based SQL. When the transform genuinely needs JS (currency's separator disambiguation), compute the values during the compatibility scan and pass them through resolved, then apply them in one batched statement.

Naming Convention

• Type id: lowercase, singular — currency, not Currency or currencies
• File: column-types/{id}.ts, export const {id}ColumnType
• Icon: type-{kebab}.tsx, export Type{Pascal}

Watch out

• Import cycles. column-types/select.ts imports select-values.ts, so select-values.ts must not import the registry — that closes a cycle and fails at module init. Inside a type's own helper module the string literal is the implementation, not a config leak.
• The client-safe boundary. registry.ts and everything it imports must stay free of @sim/db, drizzle-orm, and next/server — the tables grid imports it directly. A React icon is fine (it's a component reference, never called server-side). Only registry.server.ts may touch drizzle.
• Don't re-export the registry from @/lib/table. 44 server modules import that barrel; routing this through it pulls @sim/emcn/icons into all of them. Deep-import @/lib/table/column-types.
• import.ts's coerceValue is a SECOND write path and is not opt-in. Importing into a column of your type always hits it, and its default arm silently String(value)s — so a missing case stores text in a column whose jsonbCast is numeric, and then every filter and sort on that column errors in Postgres. Add a case, even though the switch compiles without one. (It is deliberately separate from the registry's coerce: an import wants an unparseable value to survive as its raw string so the row error can name it.)
• CSV inference is an ordered heuristic in import.ts, deliberately not registry-driven. A new type is not inferred from a CSV unless you extend inferColumnType — usually you should not, since inference cannot supply configuration (an option set, a currency code).

If your type owns metadata, read this

Registering the type is compiler-enforced. Registering its metadata is not, and that is where the remaining manual work lives. A key like precision has to be added in each of these, none of which will fail to compile if you forget:

normalizeColumn, buildConvertedColumn, and the undo snapshot read TYPE_SPECIFIC_COLUMN_KEYS generically, so those three are already zero-edit.

Known gap: the metadata-only update path is ~6 near-identical copies (service + 2 routes + copilot). A metadataUpdate descriptor on ColumnTypeServerDefinition would collapse them; until that exists, copy currency's.

Checklist Before Finishing

• Added to the ColumnType union in column-types/types.ts
• column-types/{id}.ts created, every interface field filled in
• Registered in both registry.ts and registry.server.ts
• Icon added, centered on the family's optical center, exported alphabetically
• migrateCellsTo / migrateCellsFrom added if the stored bytes change
• New metadata keys added to TYPE_SPECIFIC_COLUMN_KEYS + FOREIGN_METADATA_VERB
• Unit tests for coerce / isCompatibleWith round-trips, verified to fail without the code
• Docs row added to apps/docs/content/docs/en/tables/index.mdx

Final Validation (Required)

1. cd apps/sim && bun run type-check — must be clean. If any file outside column-types/ errors, that file has a hardcoded type list; fix it to read the registry.
2. Grep for leaks — grep -rnE "(===|!==) '{id}'|case '{id}':" apps/sim --include='*.ts' --include='*.tsx' | grep -v column-types/. (All three forms: a plain !== and a case are how half of currency's real branches are written.) Hits are expected; judge each. A hit is fine when it mounts a specific React component or encodes a genuinely one-off behavior (json's mono textarea, date's timezone-aware parsing). A hit is a leak when it restates something the registry could answer — an icon, a label, a colour, an operator set, a cast, a coercion. Leaks get a registry field, not a new branch.
3. Run the suite — bunx vitest run lib/table 'app/workspace/[workspaceId]/tables' lib/api app/api/table app/api/v1 lib/copilot/tools/server/table. Existing tests must pass unchanged; needing to edit one means you changed behavior for the other types.
4. bun run lint:check, bun run check:api-validation, bun run check:client-boundary from the repo root.
5. Exercise it in the running app on a table with one column of every type: create, edit inline / in the expanded popover / in the row modal, paste from a spreadsheet, filter, sort, convert to and from other types, export CSV, undo a column delete.