Use single expr via stdin when invoking nix-build

nox/review.py

@@ -11,17 +11,21 @@
 from .nixpkgs_repo import get_repo, packages, packages_for_sha
 
 
-def get_build_command(args, attrs, path):
+def get_build_command(args):
     """ Get the appropriate command to use to build the given attributes """
     command = ['nix-build']
     command += args
-    for a in attrs:
-        command.append('-A')
-        command.append(a)
-    command.append(path)
+    command.append("-E")
+    command.append("-")
+
     return command
 
 
+def get_build_expr(attrs, path):
+    """ Get the appropriate expression to use to build the given attributes """
+    return "with import {} {{}}; [ {} ]".format(path, ' '.join(attrs))
+
+
 def build_in_path(args, attrs, path, dry_run=False):
     """Build the given package attributes in the given nixpkgs path"""
     if not attrs:
@@ -33,15 +37,19 @@ def build_in_path(args, attrs, path, dry_run=False):
     click.echo('Building in {}: {}'.format(click.style(result_dir, bold=True),
                                            click.style(' '.join(attrs), bold=True)))
 
-    command = get_build_command(args, attrs, canonical_path)
+    expr = get_build_expr(attrs, canonical_path)
+    command = get_build_command(args)
 
-    click.echo('Invoking {}'.format(' '.join(command)))
+    click.echo('Invoking {} with expression {}'.format(' '.join(command), expr))
 
     if dry_run:
         return
 
     try:
-        subprocess.check_call(command, cwd=result_dir)
+        with tempfile.SpooledTemporaryFile() as expr_f:
+            expr_f.write(expr.encode('utf-8'))
+            expr_f.seek(0)
+            subprocess.check_call(command, cwd=result_dir, stdin=expr_f)
     except subprocess.CalledProcessError:
         click.secho('The invocation of "{}" failed'.format(' '.join(command)), fg='red')
         sys.exit(1)

nox/tests/test_review.py

@@ -5,12 +5,17 @@
 
 class TestReview(unittest.TestCase):
     def test_get_build_command(self):
-        result = review.get_build_command([], ["nox"], ".")
-        self.assertEqual(["nix-build", "-A", "nox", "."], result)
+        result = review.get_build_command([])
+        self.assertEqual(["nix-build", "-E", "-"], result)
+
+    def test_get_build_expr(self):
+        result = review.get_build_expr(["nox"], "./.")
+        self.assertEqual("with import ./. {}; [ nox ]", result)
 
     def test_build_in_path(self):
         # Just do a dry run to make sure there aren't any exceptions
         self.assertIs(None, review.build_in_path([], ["nox"], ".", dry_run=True))
+        self.assertIs(None, review.build_in_path([], ["nox"], "./.", dry_run=True))
 
     def test_differences(self):
         # Tuples of <old set>, <new set>, <expected difference>