sql: Add NULL support to database wrappers

src/sql/api.ts

@@ -3,7 +3,7 @@ import * as sql from "sql-bricks-postgres";
 import { Id } from "../model";
 
 export interface Row {
-  [key: string]: string;
+  [key: string]: string | null;
 }
 
 export interface Transaction {

src/sql/util.ts

@@ -3,15 +3,23 @@ import snakeCase from "snake-case";
 import { Row } from "./api";
 
 interface ColMapper<F> {
-  _read(str: string): F;
+  _read(str: string | null): F;
 
-  _write(val: F): string;
+  _write(val: F): string | null;
 }
 
 type Spec<R> = {
   [K in keyof R]: ColMapper<R[K]>;
 };
 
+function _nn(str: string | null): string {
+  if (str === null) {
+    throw new Error("Unexpected NULL returned from database");
+  }
+
+  return str;
+}
+
 /**
  * Function objects describing the precise way in which our SQL driver
  * transmits and receives values to the database as strings. Note that we could
@@ -20,25 +28,31 @@ type Spec<R> = {
  */
 export const T = {
   bigint: {
-    _read: (str: string) => BigInt(str),
+    _read: (str: string) => BigInt(_nn(str)),
     _write: (val: bigint) => val.toString(),
   },
   boolean: {
-    _read: (str: string) => str === "true",
+    _read: (str: string) => _nn(str) === "true",
     _write: (val: boolean) => val.toString(),
   },
   number: {
-    _read: (str: string) => parseInt(str),
+    _read: (str: string) => parseInt(_nn(str)),
     _write: (val: number) => val.toString(),
   },
   string: {
-    _read: (str: string) => str,
+    _read: (str: string) => _nn(str),
     _write: (val: string) => val,
   },
   Date: {
-    _read: (str: string) => new Date(str),
+    _read: (str: string) => new Date(_nn(str)),
     _write: (val: Date) => val.toISOString(),
   },
+  nullable: <F>(inner: ColMapper<F>) => ({
+    _read: (str: string | null) =>
+      str !== null ? inner._read(str) : undefined,
+    _write: (val: F | undefined) =>
+      val !== undefined ? inner._write(val) : null,
+  }),
 };
 
 /**