Use lit_test for driver (#1037)

toolchain/driver/BUILD

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 load("//bazel/fuzzing:rules.bzl", "cc_fuzz_test")
+load("//bazel/testing:lit_test.bzl", "lit_test")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -53,12 +54,12 @@ cc_binary(
     ],
 )
 
-# FIXME: No support for LLVM's lit-style command line & FileCheck tests.
-#
-#lit_test(
-#    name = "carbon_test.carbon",
-#    data = [
-#        ":carbon",
-#        "@llvm-project//llvm:FileCheck",
-#    ],
-#)
+lit_test(
+    name = "carbon_lit_test",
+    data = [
+        ":carbon",
+        "@llvm-project//llvm:FileCheck",
+        "@llvm-project//llvm:not",
+    ],
+    test_dir = "testdata",
+)

toolchain/driver/carbon_test.carbon

@@ -1,24 +0,0 @@
-// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
-// Exceptions. See /LICENSE for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-// FIXME: We need to figure out how to integrate this style of integration
-// testing with Bazel.
-//
-// RUN: driver/carbon dump-tokens %s | FileCheck %s --check-prefix=TOKENS
-
-fn run(String program) {
-  return True;
-}
-
-// TOKENS: token: { index:  0, kind:       'FnKeyword', line: 4, column:  1, indent: 1, spelling: 'fn' }
-// TOKENS: token: { index:  1, kind:      'Identifier', line: 4, column:  4, indent: 1, spelling: 'run', identifier: 0 }
-// TOKENS: token: { index:  2, kind:       'OpenParen', line: 4, column:  7, indent: 1, spelling: '(', closing_token: 5 }
-// TOKENS: token: { index:  3, kind:      'Identifier', line: 4, column:  8, indent: 1, spelling: 'String', identifier: 1 }
-// TOKENS: token: { index:  4, kind:      'Identifier', line: 4, column: 15, indent: 1, spelling: 'program', identifier: 2 }
-// TOKENS: token: { index:  5, kind:      'CloseParen', line: 4, column: 22, indent: 1, spelling: ')', opening_token: 2 }
-// TOKENS: token: { index:  6, kind:  'OpenCurlyBrace', line: 4, column: 24, indent: 1, spelling: '{', closing_token: 10 }
-// TOKENS: token: { index:  7, kind:   'ReturnKeyword', line: 5, column:  3, indent: 3, spelling: 'return' }
-// TOKENS: token: { index:  8, kind:      'Identifier', line: 5, column: 10, indent: 3, spelling: 'True', identifier: 3 }
-// TOKENS: token: { index:  9, kind:            'Semi', line: 5, column: 14, indent: 3, spelling: ';' }
-// TOKENS: token: { index: 10, kind: 'CloseCurlyBrace', line: 6, column:  1, indent: 1, spelling: '}', opening_token: 6 }

toolchain/driver/testdata/carbon_test.carbon

@@ -0,0 +1,27 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// FIXME: We need to figure out how to integrate this style of integration
+// testing with Bazel.
+//
+// RUN: %{carbon} dump-tokens %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false \
+// RUN:   --check-prefix=TOKENS %s
+
+fn run(String program) {
+  return True;
+}
+
+// TOKENS: token: { index:  0, kind:       'FnKeyword', line: 12, column:   1, indent: 1, spelling: 'fn', has_trailing_space: true }
+// TOKENS: token: { index:  1, kind:      'Identifier', line: 12, column:   4, indent: 1, spelling: 'run', identifier: 0 }
+// TOKENS: token: { index:  2, kind:       'OpenParen', line: 12, column:   7, indent: 1, spelling: '(', closing_token: 5 }
+// TOKENS: token: { index:  3, kind:      'Identifier', line: 12, column:   8, indent: 1, spelling: 'String', identifier: 1, has_trailing_space: true }
+// TOKENS: token: { index:  4, kind:      'Identifier', line: 12, column:  15, indent: 1, spelling: 'program', identifier: 2 }
+// TOKENS: token: { index:  5, kind:      'CloseParen', line: 12, column:  22, indent: 1, spelling: ')', opening_token: 2, has_trailing_space: true }
+// TOKENS: token: { index:  6, kind:  'OpenCurlyBrace', line: 12, column:  24, indent: 1, spelling: '{', closing_token: 10, has_trailing_space: true }
+// TOKENS: token: { index:  7, kind:   'ReturnKeyword', line: 13, column:   3, indent: 3, spelling: 'return', has_trailing_space: true }
+// TOKENS: token: { index:  8, kind:      'Identifier', line: 13, column:  10, indent: 3, spelling: 'True', identifier: 3 }
+// TOKENS: token: { index:  9, kind:            'Semi', line: 13, column:  14, indent: 3, spelling: ';', has_trailing_space: true }
+// TOKENS: token: { index: 10, kind: 'CloseCurlyBrace', line: 14, column:   1, indent: 1, spelling: '}', opening_token: 6, has_trailing_space: true }
+// TOKENS: token: { index: 11, kind:       'EndOfFile', line: 27, column: 105, indent: 1, spelling: '' }

toolchain/driver/testdata/lit.cfg.py

@@ -0,0 +1,32 @@
+__copyright__ = """
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+"""
+
+import lit.formats
+import os
+
+
+# This is a provided variable, ignore the undefined name warning.
+config = config  # noqa: F821
+
+
+def fullpath(relative_path):
+    return os.path.join(os.environ["TEST_SRCDIR"], relative_path)
+
+
+config.name = "lit"
+config.suffixes = [".carbon"]
+config.test_format = lit.formats.ShTest()
+
+config.substitutions.append(
+    (
+        "%{carbon}",
+        fullpath("carbon/toolchain/driver/carbon"),
+    )
+)
+config.substitutions.append(("%{not}", fullpath("llvm-project/llvm/not")))
+config.substitutions.append(
+    ("%{FileCheck}", fullpath("llvm-project/llvm/FileCheck"))
+)