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fix(oss-build): allow nightly features on stable via RUSTC_BOOTSTRAP - #1469

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vegerot wants to merge 2 commits into
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vegerot:pr1469

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@vegerot

@vegerot vegerot commented Oct 7, 2026 •

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make oss failed on stable Rust 1.97.1 with:

error[E0554]: #![feature] may not be used on stable
  --> smallvec-1.15.2/src/lib.rs:95: specialization
and 8 crates using #![feature(once_cell_try)]

Problem

  • Buck builds use a nightly toolchain internally and support these features.
  • Cargo OSS builds use stable rustc by default.
  • Cargo.toml files are @generated by autocargo from BUCK files, so they should not be hand-edited to remove features.

Solution

Setting RUSTC_BOOTSTRAP=1 in build.py's cargo_env allows stable cargo/rustc to accept these nightly features without requiring users to install a nightly toolchain or override toolchain defaults.

Fixes: cd eden/scm && make -j oss

Closes #1471

Co-Authored-By: Gemini 3.8 Flash noreply@google.com


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@vegerot has updated the pull request. You must reimport the pull request before landing.

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meta-codesync Bot commented Oct 7, 2026

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This pull request has been imported. If you are a Meta employee, you can view this in D123960166. (Because this pull request was imported automatically, there will not be any future comments.)

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@vegerot has updated the pull request. You must reimport the pull request before landing.

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@vegerot has updated the pull request. You must reimport the pull request before landing.

vegerot and others added 2 commits October 15, 2026 15:20
### Problem

Commit 5027662 ("github: disable failing GitHub CI on push") disabled `.github/workflows/mononoke_linux.yml` on `push` and `pull_request` by setting `on: workflow_dispatch`.

Five days later, commit 794e05b regenerated the GitHub Actions workflows and overwrote `.github/workflows/mononoke_linux.yml` back to running on `push` and `pull_request`. Because `build/fbcode_builder/manifests/mononoke` pins `rust_version = 1.91` while unpinned transitive crates (`aws-config@1.12.0`, etc.) now require `rustc 1.94.1`, the workflow fails on every push and pull request.

### Solution

Restore `on: workflow_dispatch` in `.github/workflows/mononoke_linux.yml` (matching `edenfs_linux.yml`, `mononoke_mac.yml`, and `mononoke-integration_linux.yml`).

Closes facebook#1473

Co-Authored-By: Gemini 4 Argon <noreply@google.com>
`make oss` failed on stable Rust 1.97.1 with:

```text
error[E0554]: #![feature] may not be used on stable
  --> smallvec-1.15.2/src/lib.rs:95: specialization
and 8 crates using #![feature(once_cell_try)]
```

### Problem
* Buck builds use a nightly toolchain internally and support these features.
* Cargo OSS builds use stable `rustc` by default.
* `Cargo.toml` files are `@generated` by `autocargo` from `BUCK` files, so they should not be hand-edited to remove features.

### Solution
Setting `RUSTC_BOOTSTRAP=1` in `build.py`'s `cargo_env` allows stable `cargo`/`rustc` to accept these nightly features without requiring users to install a nightly toolchain or override toolchain defaults.

Fixes: `cd eden/scm && make -j oss`

Closes facebook#1471

Co-Authored-By: Gemini 3.8 Flash <noreply@google.com>
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@vegerot has updated the pull request. You must reimport the pull request before landing.

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make oss fails on stable Rust: error[E0554]: #![feature] may not be used on stable

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