This "declarations" folder exists to fix broken TypeScript type definitions for the Apache Arrow project.

The apache-arrow 0.17.0 npm package fails to compile in modern TypeScript. The issue is tracked here: https://issues.apache.org/jira/browse/ARROW-8394

As a workaround, we provide a patched set of Arrow type declarations in this folder.

These are the changes:

• Copy the entirety of ./node_modules/apache-arrow into ./declarations/apache-arrow
• Delete all non .d.ts files, except for package.json, from the copied directory:

  $ find declarations/apache-arrow ! -name "*d.ts" -and ! -name "package.json" -type f -delete
  

• Add a // @ts-nocheck comment to the top of the declaration files that cause errors:
  • declarations/apache-arrow/column.d.ts
  • declarations/apache-arrow/ipc/reader.d.ts
  • declarations/apache-arrow/recordbatch.d.ts
• Add the following bits to tsconfig.json:

  "compilerOptions": {
    "paths": {
      "*": [
        "./*",
        "../declarations/*"
      ]
    }
  }
  

When apache-arrow is fixed, we should back out these changes!