Add check 'missing-patch-comment' using rust and rnix

.github/workflows/main.yaml

@@ -15,4 +15,4 @@ jobs:
       uses: cachix/install-nix-action@v12
 
     - name: Run tests
-      run: nix-shell --run ./run-tests.py
+      run: nix run -c ./run-tests.py

.gitignore

@@ -0,0 +1 @@
+ast-checks/target

ast-checks/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "nixpkgs-hammer-ast-checks"
+version = "0.0.0"
+authors = ["Robert T. McGibbon <[email protected]>"]
+edition = "2018"
+
+[[bin]]
+name = "missing-patch-comment"
+path = "src/missing-patch-comment.rs"
+
+[dependencies]
+codespan = "0.11"
+rnix = "0.7.0"
+rowan = { version = "0.6.2", features = [ "serde1" ] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"

ast-checks/src/comment_finders.rs

@@ -0,0 +1,34 @@
+use crate::tree_utils::{next_siblings, prev_siblings, walk_kind};
+use rnix::{NodeOrToken, SyntaxElement, SyntaxKind::*, SyntaxNode};
+
+pub fn find_comment_within(node: &SyntaxNode) -> Option<String> {
+    // Find the first `TOKEN_COMMENT` within.
+    let tok = walk_kind(node, TOKEN_COMMENT).next()?;
+    // Iterate over sibling comments and concatenate them.
+    let node_iter = next_siblings(&tok);
+    let doc = collect_comment_text(node_iter);
+    Some(doc).filter(|it| !it.is_empty())
+}
+
+pub fn find_comment_above(node: &SyntaxNode) -> Option<String> {
+    // Note: The `prev_siblings` iterator includes self, which
+    // is not a `TOKEN_COMMENT`, so we need to skip one.
+    let node_iter = prev_siblings(&NodeOrToken::Node(node.clone())).skip(1);
+    let doc = collect_comment_text(node_iter);
+    Some(doc).filter(|it| !it.is_empty())
+}
+
+fn collect_comment_text(node_iter: impl Iterator<Item = SyntaxElement>) -> String {
+    // Take text of all immediately subsequent `TOKEN_COMMENT`s,
+    // skipping over whitespace-only tokens.
+    // Note this would be more clearly written using `map_while`, but that
+    // does not seem to be in Rust stable yet.
+    node_iter
+        .filter_map(|node| node.into_token())
+        .take_while(|tok| tok.kind() == TOKEN_COMMENT || tok.kind().is_trivia())
+        .map(|tok| tok.text().to_string())
+        .map(|s| s.trim_start_matches('#').trim().to_string())
+        .filter(|s| !s.is_empty())
+        .collect::<Vec<_>>()
+        .join("\n")
+}

ast-checks/src/common_structs.rs

@@ -0,0 +1,16 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct SourceLocation {
+    pub column: usize,
+    pub line: usize,
+    pub file: String,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct NixpkgsHammerMessage {
+    pub cond: bool,
+    pub locations: Vec<SourceLocation>,
+    pub msg: &'static str,
+    pub name: &'static str,
+}