Early fail for nodejs versions >= 15

internal.nix

@@ -1,6 +1,8 @@
-{ nodejs, stdenv, mkShell, lib, fetchurl, writeText, writeTextFile, runCommand, fetchFromGitHub }:
+{ nodejs-14_x, stdenv, mkShell, lib, fetchurl, writeText, writeTextFile, runCommand, fetchFromGitHub }:
 rec {
-  default_nodejs = nodejs;
+  # Versions >= 15 use npm >= 7, which uses npm lockfile version 2, which we don't support yet
+  # See the assertion in the node_modules function
+  default_nodejs = nodejs-14_x;
 
 
   # builtins.fetchGit wrapper that ensures compatibility with Nix 2.3 and Nix 2.4
@@ -318,6 +320,8 @@ rec {
     , passthru ? { }
     , ...
     }@args:
+      assert lib.versionAtLeast nodejs.version "15.0" ->
+        throw "npmlock2nix is called with nodejs version ${nodejs.version}, which is currently not supported, see https://github.com/nix-community/npmlock2nix/issues/153 for more information";
       assert (builtins.typeOf preInstallLinks != "set") ->
         throw "`preInstallLinks` must be an attributeset of attributesets";
       let

tests/examples-projects/single-dependency-lockfilev2/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "single-dependency",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "leftpad": "0.0.1"
+  }
+}

tests/examples-projects/single-dependency-lockfilev2/shell.nix

@@ -0,0 +1,4 @@
+{ pkgs ? import ../../../nix { } }:
+pkgs.npmlock2nix.shell {
+  src = ./.;
+}

tests/integration-tests/default.nix

@@ -1,4 +1,4 @@
-{ npmlock2nix, testLib, callPackage, libwebp, runCommandNoCC, python3 }:
+{ npmlock2nix, testLib, nodejs-16_x, callPackage, libwebp, runCommandNoCC, python3 }:
 testLib.makeIntegrationTests {
   leftpad = {
     description = "Require a node dependency inside the shell environment";
@@ -246,4 +246,42 @@ testLib.makeIntegrationTests {
       works
     '';
   };
+
+  npm7-old-lockfile = {
+    description = "NPM >= 7 isn't supported right now because it uses a newer lockfile version";
+    shell = npmlock2nix.shell {
+      src = ../examples-projects/single-dependency;
+      nodejs = nodejs-16_x;
+    };
+    evalFailure = true;
+    status = 1;
+    expected = "";
+    # Would fail with
+    # npm WARN old lockfile The package-lock.json file was created with an old version of npm,
+    # npm WARN old lockfile so supplemental metadata must be fetched from the registry.
+    # npm ERR! Error: EACCES: permission denied, open '/build/package-lock.json'
+    expected-stderr = {
+      contains = ''
+        error: [npmlock2nix] npmlock2nix is called with nodejs version 16.13.0, which is currently not supported, see https://github.com/nix-community/npmlock2nix/issues/153 for more information
+      '';
+    };
+  };
+
+  npm7-new-lockfile = {
+    description = "NPM >= 7 isn't supported right now because it uses a newer lockfile version";
+    shell = npmlock2nix.shell {
+      src = ../examples-projects/single-dependency-lockfilev2;
+      nodejs = nodejs-16_x;
+    };
+    evalFailure = true;
+    status = 1;
+    expected = "";
+    # Would fail with
+    # npm ERR! request to https://registry.npmjs.org/leftpad/-/leftpad-0.0.1.tgz failed: cache mode is 'only-if-cached' but no cached response is available.
+    expected-stderr = {
+      contains = ''
+        error: [npmlock2nix] npmlock2nix is called with nodejs version 16.13.0, which is currently not supported, see https://github.com/nix-community/npmlock2nix/issues/153 for more information
+      '';
+    };
+  };
 }

tests/node-modules.nix

@@ -75,9 +75,15 @@ testLib.runTests {
   testNodeModulesAcceptsCustomNodejs = {
     expr = (npmlock2nix.node_modules {
       src = ./examples-projects/no-dependencies;
-      nodejs = "our-custom-nodejs-package";
+      nodejs = {
+        pname = "our-custom-nodejs-package";
+        version = "14.12.34";
+      };
     }).nodejs;
-    expected = "our-custom-nodejs-package";
+    expected = {
+      pname = "our-custom-nodejs-package";
+      version = "14.12.34";
+    };
   };
 
   testNodeModulesPropagatesNodejs =