feat(node): parse arrow types in alterColumns() (#2208)

Previously, users could only specify new data types in `alterColumns` as
strings:

```ts
await tbl.alterColumns([
  path: "price",
  dataType: "float"
]);
```

But this has some problems:

1. It wasn't clear what were valid types
2. It was impossible to specify nested types, like lists and vector
columns.

This PR changes it to take an Arrow data type, similar to how the Python
API works. This allows casting vector types:

```ts
await tbl.alterColumns([
  {
    path: "vector",
    dataType: new arrow.FixedSizeList(
      2,
      new arrow.Field("item", new arrow.Float16(), false),
    ),
  },
]);
```

Closes #2185

nodejs/lancedb/arrow.ts

@@ -8,7 +8,11 @@ import {
   Bool,
   BufferType,
   DataType,
+  DateUnit,
+  Date_,
+  Decimal,
   Dictionary,
+  Duration,
   Field,
   FixedSizeBinary,
   FixedSizeList,
@@ -21,12 +25,15 @@ import {
   LargeBinary,
   List,
   Null,
+  Precision,
   RecordBatch,
   RecordBatchFileReader,
   RecordBatchFileWriter,
   RecordBatchStreamWriter,
   Schema,
   Struct,
+  Timestamp,
+  Type,
   Utf8,
   Vector,
   makeVector as arrowMakeVector,
@@ -1170,3 +1177,137 @@ function validateSchemaEmbeddings(
 
   return new Schema(fields, schema.metadata);
 }
+
+interface JsonDataType {
+  type: string;
+  fields?: JsonField[];
+  length?: number;
+}
+
+interface JsonField {
+  name: string;
+  type: JsonDataType;
+  nullable: boolean;
+  metadata: Map<string, string>;
+}
+
+// Matches format of https://github.com/lancedb/lance/blob/main/rust/lance/src/arrow/json.rs
+export function dataTypeToJson(dataType: DataType): JsonDataType {
+  switch (dataType.typeId) {
+    // For primitives, matches https://github.com/lancedb/lance/blob/e12bb9eff2a52f753668d4b62c52e4d72b10d294/rust/lance-core/src/datatypes.rs#L185
+    case Type.Null:
+      return { type: "null" };
+    case Type.Bool:
+      return { type: "bool" };
+    case Type.Int8:
+      return { type: "int8" };
+    case Type.Int16:
+      return { type: "int16" };
+    case Type.Int32:
+      return { type: "int32" };
+    case Type.Int64:
+      return { type: "int64" };
+    case Type.Uint8:
+      return { type: "uint8" };
+    case Type.Uint16:
+      return { type: "uint16" };
+    case Type.Uint32:
+      return { type: "uint32" };
+    case Type.Uint64:
+      return { type: "uint64" };
+    case Type.Int: {
+      const bitWidth = (dataType as Int).bitWidth;
+      const signed = (dataType as Int).isSigned;
+      const prefix = signed ? "" : "u";
+      return { type: `${prefix}int${bitWidth}` };
+    }
+    case Type.Float: {
+      switch ((dataType as Float).precision) {
+        case Precision.HALF:
+          return { type: "halffloat" };
+        case Precision.SINGLE:
+          return { type: "float" };
+        case Precision.DOUBLE:
+          return { type: "double" };
+      }
+      throw Error("Unsupported float precision");
+    }
+    case Type.Float16:
+      return { type: "halffloat" };
+    case Type.Float32:
+      return { type: "float" };
+    case Type.Float64:
+      return { type: "double" };
+    case Type.Utf8:
+      return { type: "string" };
+    case Type.Binary:
+      return { type: "binary" };
+    case Type.LargeUtf8:
+      return { type: "large_string" };
+    case Type.LargeBinary:
+      return { type: "large_binary" };
+    case Type.List:
+      return {
+        type: "list",
+        fields: [fieldToJson((dataType as List).children[0])],
+      };
+    case Type.FixedSizeList: {
+      const fixedSizeList = dataType as FixedSizeList;
+      return {
+        type: "fixed_size_list",
+        fields: [fieldToJson(fixedSizeList.children[0])],
+        length: fixedSizeList.listSize,
+      };
+    }
+    case Type.Struct:
+      return {
+        type: "struct",
+        fields: (dataType as Struct).children.map(fieldToJson),
+      };
+    case Type.Date: {
+      const unit = (dataType as Date_).unit;
+      return {
+        type: unit === DateUnit.DAY ? "date32:day" : "date64:ms",
+      };
+    }
+    case Type.Timestamp: {
+      const timestamp = dataType as Timestamp;
+      const timezone = timestamp.timezone || "-";
+      return {
+        type: `timestamp:${timestamp.unit}:${timezone}`,
+      };
+    }
+    case Type.Decimal: {
+      const decimal = dataType as Decimal;
+      return {
+        type: `decimal:${decimal.bitWidth}:${decimal.precision}:${decimal.scale}`,
+      };
+    }
+    case Type.Duration: {
+      const duration = dataType as Duration;
+      return { type: `duration:${duration.unit}` };
+    }
+    case Type.FixedSizeBinary: {
+      const byteWidth = (dataType as FixedSizeBinary).byteWidth;
+      return { type: `fixed_size_binary:${byteWidth}` };
+    }
+    case Type.Dictionary: {
+      const dict = dataType as Dictionary;
+      const indexType = dataTypeToJson(dict.indices);
+      const valueType = dataTypeToJson(dict.valueType);
+      return {
+        type: `dict:${valueType.type}:${indexType.type}:false`,
+      };
+    }
+  }
+  throw new Error("Unsupported data type");
+}
+
+function fieldToJson(field: Field): JsonField {
+  return {
+    name: field.name,
+    type: dataTypeToJson(field.type),
+    nullable: field.nullable,
+    metadata: field.metadata,
+  };
+}