fix(gmail): decode message bodies by declared charset instead of dropping non-UTF-8 (P1 data loss)

[bhekanik]

Problem (P1 data loss)

base64_decode_url ended in String::from_utf8(bytes)? and walk_parts called it via .ok(). Gmail returns each part's ORIGINAL bytes untranscoded, so a charset=windows-1252/iso-8859-1/shift_jis body (e.g. 0xE9=é, 0x92=') failed strict UTF-8 → None → text_plain/text_html never set → the entire body silently vanished (envelope/subject/snippet remained). IMAP path was unaffected.

Fix

Split base64→bytes from bytes→string; decode each text leaf with its declared Content-Type charset via encoding_rs (default UTF-8, lossy fallback — content is never dropped). charset_from_content_type parses the charset= param (case-insensitive, quote-stripped). extract_body signature preserved; provider logic stays in the provider crate. Added encoding_rs (already locked transitively via mail-parser). 3 regression tests; 70 provider-gmail tests pass.

CI note: workspace clippy red on pre-existing 1.97 lints until #111 merges; will rebase (Cargo.lock).

---

Summary by cubic

Decode Gmail message bodies using the charset declared in Content-Type instead of assuming UTF‑8, preventing non‑UTF‑8 text from being dropped. Defaults to UTF‑8; unknown labels use a lossy fallback so content isn’t lost.

• Bug Fixes

  • Split base64→bytes from bytes→string; decode by declared charset via encoding_rs.
  • Parse charset= from Content-Type (case-insensitive, strips quotes).
  • Apply to text/plain, text/html, and text/calendar; extract_body unchanged; IMAP path unaffected.
  • Added regression tests for windows-1252, quoted ISO-8859-1, and UTF‑8 multibyte.

• Dependencies

  • Added encoding_rs to the workspace and provider-gmail.

^{Written for commit e5ec17f. Summary will update on new commits.}

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Project	Deployment	Actions	Updated (UTC)
mxr-mail	Ready	Preview, Comment	Jul 11, 2026 2:27am

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 628c4348-ba43-4567-be49-7b81ef4aa650

📥 Commits

Reviewing files that changed from the base of the PR and between ca2b24b and e5ec17f.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (3)

• Cargo.toml
• crates/provider-gmail/Cargo.toml
• crates/provider-gmail/src/parse.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/gmail-charset-body-loss

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[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}