[ZEPPELIN-6699] React remote CSV export omits the UTF-8 BOM that the Angular and classic paths write

[xhaktm00]

What is this PR for?

The React remote builds its CSV export by hand and hands the string straight to a Blob with no UTF-8 BOM, so Excel reads it in the system code page and garbles non-ASCII data. The classic path prepends one through saveAsService, and the Angular path gets one from XLSX.writeFile(), so only this export was missing it. ZEPPELIN-672 added the BOM for exactly this reason.

- const blob = new Blob([content], { type: 'text/plain;charset=utf-8' });
+ const BOM = '\uFEFF';
+ const blob = new Blob([BOM, content], { type: 'text/plain;charset=utf-8' });

The xlsx branch is left alone, since that format carries its own encoding.

What type of PR is it?

Bug Fix

Todos

• Prepend the BOM in the React remote CSV export
• Add a regression test asserting the saved bytes

What is the Jira issue?

• ZEPPELIN-6699

How should this be tested?

New spec exportFile.spec.ts mocks file-saver and inspects the bytes handed to saveAs, since Blob.text() decodes and drops a leading BOM.

cd zeppelin-web-angular/projects/zeppelin-react && npm test

Result: Tests 1 failed | 67 passed (68). The one failure is HTMLRenderer.spec.tsx > highlights a code block, which fails the same way on origin/master without this change. Running the new spec alone passes:

npx vitest run src/utils/exportFile.spec.ts   → Tests 2 passed (2)

Reverting only the production change makes it fail with expected [ 110, 97, 109 ] to deeply equal [ 239, 187, 191 ], so it does catch the defect.

Manual: run a paragraph whose table result contains non-ASCII text, open the published paragraph with ?react=true, and choose "Export all data as csv". The file now starts with EF BB BF and opens in Excel with the text intact.

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No — the BOM only makes the React export match what the other two paths already write
• Does this needs documentation? No

Note: the issue scopes this to CSV and TSV, but the React remote has no TSV path, since exportFile() only takes 'csv' | 'xlsx'. I'll file that parity gap separately; the BOM sits on the shared branch, so a TSV path added there inherits it.

[voidmatcha]

LGTM 👍