From aaa00976aeab36dcba56d43eed6d8ab295eca1eb Mon Sep 17 00:00:00 2001
From: Zanie Blue <contact@zanie.dev>
Date: Thu, 4 Jan 2024 09:19:00 -0600
Subject: [PATCH] Generate deterministic ids when formatting notebooks (#9359)
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When formatting notebooks, we populate the `id` field for cells that do
not have one. Previously, we generated a UUID v4 which resulted in
non-deterministic formatting. Here, we generate the UUID from a seeded
random number generator instead of using true randomness. For example,
here are the first five ids it would generate:

```
7fb27b94-1602-401d-9154-2211134fc71a
acae54e3-7e7d-407b-bb7b-55eff062a284
9a63283c-baf0-4dbc-ab1f-6479b197f3a8
8dd0d809-2fe7-4a7c-9628-1538738b07e2
72eea511-9410-473a-a328-ad9291626812
```

We also add a check that an id is not present in another cell to prevent
accidental introduction of duplicate ids.

The specification is lax, and we could just use incrementing integers
e.g. `0`, `1`, ... but I have a minor preference for retaining the UUID
format. Some discussion
[here](https://github.com/astral-sh/ruff/pull/9359#discussion_r1439607121)
— I'm happy to go either way though.

Discovered via #9293
---
 Cargo.lock                           |  1 +
 crates/ruff_notebook/Cargo.toml      |  1 +
 crates/ruff_notebook/src/notebook.rs | 32 +++++++++++++++++++++++++---
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 9e31c4bdf3..ac47fb91e2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2259,6 +2259,7 @@ dependencies = [
  "insta",
  "itertools 0.12.0",
  "once_cell",
+ "rand",
  "ruff_diagnostics",
  "ruff_source_file",
  "ruff_text_size",
diff --git a/crates/ruff_notebook/Cargo.toml b/crates/ruff_notebook/Cargo.toml
index 517a233455..524cfb4eb9 100644
--- a/crates/ruff_notebook/Cargo.toml
+++ b/crates/ruff_notebook/Cargo.toml
@@ -25,6 +25,7 @@ serde_json = { workspace = true }
 serde_with = { workspace = true, default-features = false, features = ["macros"] }
 thiserror = { workspace = true }
 uuid = { workspace = true }
+rand = { workspace = true }
 
 [dev-dependencies]
 insta = { workspace = true }
diff --git a/crates/ruff_notebook/src/notebook.rs b/crates/ruff_notebook/src/notebook.rs
index ddc558ba21..94d5a312c6 100644
--- a/crates/ruff_notebook/src/notebook.rs
+++ b/crates/ruff_notebook/src/notebook.rs
@@ -1,4 +1,5 @@
 use std::cmp::Ordering;
+use std::collections::HashSet;
 use std::fs::File;
 use std::io::{BufReader, Cursor, Read, Seek, SeekFrom, Write};
 use std::path::Path;
@@ -6,10 +7,10 @@ use std::{io, iter};
 
 use itertools::Itertools;
 use once_cell::sync::OnceCell;
+use rand::{Rng, SeedableRng};
 use serde::Serialize;
 use serde_json::error::Category;
 use thiserror::Error;
-use uuid::Uuid;
 
 use ruff_diagnostics::{SourceMap, SourceMarker};
 use ruff_source_file::{NewlineWithTrailingNewline, OneIndexed, UniversalNewlineIterator};
@@ -145,7 +146,23 @@ impl Notebook {
         // Add cell ids to 4.5+ notebooks if they are missing
         // https://github.com/astral-sh/ruff/issues/6834
         // https://github.com/jupyter/enhancement-proposals/blob/master/62-cell-id/cell-id.md#required-field
+        // https://github.com/jupyter/enhancement-proposals/blob/master/62-cell-id/cell-id.md#questions
         if raw_notebook.nbformat == 4 && raw_notebook.nbformat_minor >= 5 {
+            // We use a insecure random number generator to generate deterministic uuids
+            let mut rng = rand::rngs::StdRng::seed_from_u64(0);
+            let mut existing_ids = HashSet::new();
+
+            for cell in &raw_notebook.cells {
+                let id = match cell {
+                    Cell::Code(cell) => &cell.id,
+                    Cell::Markdown(cell) => &cell.id,
+                    Cell::Raw(cell) => &cell.id,
+                };
+                if let Some(id) = id {
+                    existing_ids.insert(id.clone());
+                }
+            }
+
             for cell in &mut raw_notebook.cells {
                 let id = match cell {
                     Cell::Code(cell) => &mut cell.id,
@@ -153,8 +170,17 @@ impl Notebook {
                     Cell::Raw(cell) => &mut cell.id,
                 };
                 if id.is_none() {
-                    // https://github.com/jupyter/enhancement-proposals/blob/master/62-cell-id/cell-id.md#questions
-                    *id = Some(Uuid::new_v4().to_string());
+                    loop {
+                        let new_id = uuid::Builder::from_random_bytes(rng.gen())
+                            .into_uuid()
+                            .as_simple()
+                            .to_string();
+
+                        if existing_ids.insert(new_id.clone()) {
+                            *id = Some(new_id);
+                            break;
+                        }
+                    }
                 }
             }
         }