new lint: faster_zipattrswith

bin/tests/data/faster_zipattrswith.nix

@@ -0,0 +1,13 @@
+{
+  # trivial case
+  _ = lib.zipAttrsWith (name: values: values) [{ a = 1; } { a = 2; b = 3; }];
+
+  # offer lint heuristically on this too
+  _ = nixpkgs.lib.zipAttrsWith (name: values: values) [{ a = 1; } { a = 2; b = 3; }];
+
+  # do not lint on `builtins`
+  _ = builtins.zipAttrsWith (name: values: values) [
+    { a = 1; }
+    { a = 2; b = 3; }
+  ];
+}

bin/tests/main.rs

@@ -19,7 +19,7 @@ mod util {
                 test_lint!($($tail)*);
         };
         ($tname:ident) => {
-            test_lint!($tname => session_info!("2.5"));
+            test_lint!($tname => session_info!("2.6"));
         };
         ($tname:ident => $sess:expr) => {
             #[test]
@@ -61,5 +61,6 @@ test_lint! {
     unquoted_uri,
     deprecated_is_null,
     empty_inherit,
-    faster_groupby => session_info!("2.5")
+    faster_groupby => session_info!("2.5"),
+    faster_zipattrswith => session_info!("2.6")
 }

bin/tests/snapshots/main__faster_zipattrswith.snap

@@ -0,0 +1,20 @@
+---
+source: bin/tests/main.rs
+expression: "&out"
+
+---
+[W16] Warning: Found lib.zipAttrsWith
+   ╭─[data/faster_zipattrswith.nix:3:7]
+   │
+ 3 │   _ = lib.zipAttrsWith (name: values: values) [{ a = 1; } { a = 2; b = 3; }];
+   ·       ────────┬───────  
+   ·               ╰───────── Prefer builtins.zipAttrsWith over lib.zipAttrsWith
+───╯
+[W16] Warning: Found lib.zipAttrsWith
+   ╭─[data/faster_zipattrswith.nix:6:7]
+   │
+ 6 │   _ = nixpkgs.lib.zipAttrsWith (name: values: values) [{ a = 1; } { a = 2; b = 3; }];
+   ·       ────────────┬───────────  
+   ·                   ╰───────────── Prefer builtins.zipAttrsWith over nixpkgs.lib.zipAttrsWith
+───╯
+

lib/src/lints.rs

@@ -16,4 +16,5 @@ lints! {
     deprecated_is_null,
     empty_inherit,
     faster_groupby,
+    faster_zipattrswith,
 }

lib/src/lints/faster_zipattrswith.rs

@@ -0,0 +1,72 @@
+use crate::{
+    make,
+    session::{SessionInfo, Version},
+    Metadata, Report, Rule, Suggestion,
+};
+
+use if_chain::if_chain;
+use macros::lint;
+use rnix::{
+    types::{Select, TypedNode},
+    NodeOrToken, SyntaxElement, SyntaxKind,
+};
+
+/// ## What it does
+/// Checks for `lib.zipAttrsWith`.
+///
+/// ## Why is this bad?
+/// Nix 2.6 introduces `builtins.zipAttrsWith` which is faster and does
+/// not require a lib import.
+///
+/// ## Example
+///
+/// ```nix
+/// lib.zipAttrsWith (name: values: values) [ {a = "x";} {a = "y"; b = "z";} ]
+/// # { a = ["x" "y"]; b = ["z"] }
+/// ```
+///
+/// Replace `lib.zipAttrsWith` with `builtins.zipAttrsWith`:
+///
+/// ```nix
+/// builtins.zipAttrsWith (name: values: values) [ {a = "x";} {a = "y"; b = "z";} ]
+/// ```
+#[lint(
+    name = "faster_zipattrswith",
+    note = "Found lib.zipAttrsWith",
+    code = 16,
+    match_with = SyntaxKind::NODE_SELECT
+)]
+struct FasterZipAttrsWith;
+
+impl Rule for FasterZipAttrsWith {
+    fn validate(&self, node: &SyntaxElement, sess: &SessionInfo) -> Option<Report> {
+        let lint_version = "2.6".parse::<Version>().unwrap();
+        if_chain! {
+            if sess.version() >= &lint_version;
+            if let NodeOrToken::Node(node) = node;
+            if let Some(select_expr) = Select::cast(node.clone());
+            if let Some(select_from) = select_expr.set();
+            if let Some(zip_attrs_with) = select_expr.index();
+
+            // a heuristic to lint on nixpkgs.lib.zipAttrsWith
+            // and lib.zipAttrsWith and its variants
+            if select_from.text().to_string() != "builtins";
+            if zip_attrs_with.text().to_string() == "zipAttrsWith";
+
+            then {
+                let at = node.text_range();
+                let replacement = {
+                    let builtins = make::ident("builtins");
+                    make::select(builtins.node(), &zip_attrs_with).node().clone()
+                };
+                let message = format!("Prefer `builtins.zipAttrsWith` over `{}.zipAttrsWith`", select_from);
+                Some(
+                    self.report()
+                        .suggest(at, message, Suggestion::new(at, replacement)),
+                )
+            } else {
+                None
+            }
+        }
+    }
+}