fix(builtins.zipAttrsWith): laziness

nix-js/runtime-ts/src/builtins/attrs.ts

@@ -107,3 +107,36 @@ export const groupBy =
     }
     return attrs;
   };
+
+export const zipAttrsWith =
+  (f: NixValue) =>
+  (list: NixValue): NixValue => {
+    const listForced = forceList(list);
+
+    // Map to collect all values for each attribute name
+    const attrMap = new Map<string, NixValue[]>();
+
+    // Iterate through each attribute set in the list
+    for (const item of listForced) {
+      const attrs = forceAttrs(item);
+
+      // Collect all attribute names and their values
+      for (const [key, value] of Object.entries(attrs)) {
+        if (!attrMap.has(key)) {
+          attrMap.set(key, []);
+        }
+        attrMap.get(key)!.push(value);
+      }
+    }
+
+    // Build the result attribute set
+    const result: Record<string, NixValue> = {};
+
+    for (const [name, values] of attrMap.entries()) {
+      // Apply f to name and values list
+      // f is curried: f name values
+      result[name] = createThunk(() => forceFunction(forceFunction(f)(name))(values));
+    }
+
+    return result;
+  };

nix-js/runtime-ts/src/builtins/index.ts

@@ -172,6 +172,7 @@ export const builtins: any = {
   intersectAttrs: mkPrimop(attrs.intersectAttrs, "intersectAttrs", 2),
   catAttrs: mkPrimop(attrs.catAttrs, "catAttrs", 2),
   groupBy: mkPrimop(attrs.groupBy, "groupBy", 2),
+  zipAttrsWith: mkPrimop(attrs.zipAttrsWith, "zipAttrsWith", 2),
 
   stringLength: mkPrimop(string.stringLength, "stringLength", 1),
   substring: mkPrimop(string.substring, "substring", 3),
@@ -247,7 +248,6 @@ export const builtins: any = {
   splitVersion: mkPrimop(misc.splitVersion, "splitVersion", 1),
   traceVerbose: mkPrimop(misc.traceVerbose, "traceVerbose", 2),
   tryEval: mkPrimop(misc.tryEval, "tryEval", 1),
-  zipAttrsWith: mkPrimop(misc.zipAttrsWith, "zipAttrsWith", 2),
 
   builtins: createThunk(() => builtins, "builtins"),
   currentSystem: createThunk(() => {

nix-js/runtime-ts/src/builtins/misc.ts

@@ -2,7 +2,7 @@
  * Miscellaneous builtin functions
  */
 
-import { force } from "../thunk";
+import { createThunk, force } from "../thunk";
 import { CatchableError } from "../types";
 import type { NixAttrs, NixBool, NixStrictValue, NixValue } from "../types";
 import { forceList, forceAttrs, forceFunction, forceStringValue, forceString } from "../type-assert";
@@ -355,37 +355,3 @@ export const tryEval = (e: NixValue): { success: NixBool; value: NixStrictValue
     }
   }
 };
-
-export const zipAttrsWith =
-  (f: NixValue) =>
-  (list: NixValue): NixValue => {
-    const listForced = forceList(list);
-
-    // Map to collect all values for each attribute name
-    const attrMap = new Map<string, NixValue[]>();
-
-    // Iterate through each attribute set in the list
-    for (const item of listForced) {
-      const attrs = forceAttrs(force(item) as NixValue);
-
-      // Collect all attribute names and their values
-      for (const [key, value] of Object.entries(attrs)) {
-        if (!attrMap.has(key)) {
-          attrMap.set(key, []);
-        }
-        attrMap.get(key)!.push(value);
-      }
-    }
-
-    // Build the result attribute set
-    const result: Record<string, NixValue> = {};
-
-    for (const [name, values] of attrMap.entries()) {
-      // Apply f to name and values list
-      // f is curried: f name values
-      const fWithName = forceFunction(f)(name);
-      result[name] = forceFunction(fWithName)(values);
-    }
-
-    return result;
-  };