GH-39255: [JS] Allow customization of schema when passing vectors to …

…table constructor (#39256)

Merge after #39254.

* Closes: #39255

js/src/builder/largebinary.ts

@@ -24,7 +24,7 @@ import { VariableWidthBuilder, BuilderOptions } from '../builder.js';
 export class LargeBinaryBuilder<TNull = any> extends VariableWidthBuilder<LargeBinary, TNull> {
     constructor(opts: BuilderOptions<LargeBinary, TNull>) {
         super(opts);
-        this._values = new BufferBuilder(new Uint8Array(0));
+        this._values = new BufferBuilder(Uint8Array);
     }
     public get byteLength(): number {
         let size = this._pendingLength + (this.length * 4);

js/src/table.ts

@@ -73,6 +73,8 @@ export class Table<T extends TypeMap = any> {
     constructor(...batches: readonly RecordBatch<T>[]);
     constructor(...columns: { [P in keyof T]: Vector<T[P]> }[]);
     constructor(...columns: { [P in keyof T]: Data<T[P]> | DataProps<T[P]> }[]);
+    constructor(schema: Schema<T>, ...columns: { [P in keyof T]: Vector<T[P]> }[]);
+    constructor(schema: Schema<T>, ...columns: { [P in keyof T]: Data<T[P]> | DataProps<T[P]> }[]);
     constructor(schema: Schema<T>, data?: RecordBatch<T> | RecordBatch<T>[]);
     constructor(schema: Schema<T>, data?: RecordBatch<T> | RecordBatch<T>[], offsets?: Uint32Array);
     constructor(...args: any[]) {
@@ -112,8 +114,8 @@ export class Table<T extends TypeMap = any> {
                 } else if (typeof x === 'object') {
                     const keys = Object.keys(x) as (keyof T)[];
                     const vecs = keys.map((k) => new Vector([x[k]]));
-                    const schema = new Schema(keys.map((k, i) => new Field(String(k), vecs[i].type, vecs[i].nullCount > 0)));
-                    const [, batches] = distributeVectorsIntoRecordBatches(schema, vecs);
+                    const batchSchema = schema ?? new Schema(keys.map((k, i) => new Field(String(k), vecs[i].type, vecs[i].nullCount > 0)));
+                    const [, batches] = distributeVectorsIntoRecordBatches(batchSchema, vecs);
                     return batches.length === 0 ? [new RecordBatch(x)] : batches;
                 }
             }

js/test/unit/table-tests.ts

@@ -151,6 +151,23 @@ describe(`Table`, () => {
             expect(i32).toEqualVector(makeVector(i32s));
         });
 
+        test(`creates a new Table from a Typed Array and force nullable`, () => {
+            const i32s = new Int32Array(arange(new Array<number>(10)));
+            const i32 = makeVector([i32s]);
+            expect(i32).toHaveLength(i32s.length);
+            expect(i32.nullCount).toBe(0);
+
+            const table = new Table(new Schema([new Field('i32', new Int32, true)]), { i32 });
+            const i32Field = table.schema.fields[0];
+
+            expect(i32Field.name).toBe('i32');
+            expect(i32).toHaveLength(i32s.length);
+            expect(i32Field.nullable).toBe(true);
+            expect(i32.nullCount).toBe(0);
+
+            expect(i32).toEqualVector(makeVector(i32s));
+        });
+
         test(`creates a new Table from Typed Arrays`, () => {
             const i32s = new Int32Array(arange(new Array<number>(10)));
             const f32s = new Float32Array(arange(new Array<number>(10)));