[libcxx] [test] Fix fs.op.proximate for windows

[mstorsjo]

Summary

Simmilar to many other similar path handling tests, convert the
test reference to preferred separators, and ifdef a few test references
that use network root names.

Additionally, generalize code for trimming off the root path for
generating relative_cwd, and for skipping the root name element
in count_path_elems.

[curdeius]

LGTM.

[• Quuxplusone]

LGTM % comments.

libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp

88

There's no subtle difference between //base and //foo, right? I wish this test'd use //foo here.

Also, please add these tests, of which all but two I would say are "missing" right now on Windows. (On POSIX they should be basically duplicates of existing tests, but we might as well test the expected output on POSIX as well.)

{"//foo/a", "//bar", "//foo/a"}
{"//foo/a", "//bar/", "//foo/a"}
{"//foo/a", "b", "//foo/a"}  // already tested
{"//foo/a", "/b", "//foo/a"}
{"//foo/a", "//bar/b", "//foo/a"}  // already tested

And these Windows-only tests using drive letters, because this is the only way to get a path with a root-name but no root-path, right?

{"C:/a", "C:/b", "../a"}
{"C:/a", "C:b", "/a"} // ??? my best guess
{"C:/a", "D:/a", "C:/a"}
{"C:/a", "D:/b", "C:/a"}
{"C:/a", "D:b", "C:/a"}
{"C:a", "C:/b", "C:a"}
{"C:a", "C:b", "C:a"}
{"C:a", "D:/a", "C:a"}
{"C:a", "D:/b", "C:a"}
{"C:a", "D:b", "C:a"}

libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03
 
-// XFAIL: LIBCXX-WINDOWS-FIXME
-
 // <filesystem>
 
 // path proximate(const path& p, error_code &ec)
 // path proximate(const path& p, const path& base = current_path())
 // path proximate(const path& p, const path& base, error_code& ec);
 
 #include "filesystem_include.h"
 #include <cassert>
 #include <cstdio>
 
 #include "test_macros.h"
 #include "count_new.h"
 #include "rapid-cxx-test.h"
 #include "filesystem_test_helper.h"
 
 
 static int count_path_elems(const fs::path& p) {
   int count = 0;
   for (auto& elem : p) {
-    if (elem != "/" && elem != "")
+    if (elem != p.root_name() && elem != "/" && elem != "")
       ++count;
   }
   return count;
 }
 
 TEST_SUITE(filesystem_proximate_path_test_suite)
 
 
TEST_CASE(basic_test) {
   const path cwd = fs::current_path();
   const path parent_cwd = cwd.parent_path();
   const path curdir = cwd.filename();
   TEST_REQUIRE(!cwd.native().empty());
   int cwd_depth = count_path_elems(cwd);
   path dot_dot_to_root;
   for (int i=0; i < cwd_depth; ++i)
     dot_dot_to_root /= "..";
-  path relative_cwd = cwd.native().substr(1);
+  path relative_cwd = cwd.native().substr(cwd.root_path().native().size());
   // clang-format off
   struct {
     fs::path input;
     fs::path base;
     fs::path expect;
   } TestCases[] = {
       {"", "", "."},
       {cwd, "a", ".."},
       {parent_cwd, "a", "../.."},
       {"a", cwd, "a"},
       {"a", parent_cwd, curdir / "a"},
       {"/", "a", dot_dot_to_root / ".."},
       {"/", "a/b", dot_dot_to_root / "../.."},
       {"/", "a/b/", dot_dot_to_root / "../.."},
       {"a", "/", relative_cwd / "a"},
       {"a/b", "/", relative_cwd / "a/b"},
       {"a", "/net", ".." / relative_cwd / "a"},
+#ifdef _WIN32
+      {"//foo/", "//foo", "//foo/"},
+      {"//foo", "//foo/", "//foo"},
+#else
       {"//foo/", "//foo", "."},
       {"//foo", "//foo/", "."},
+#endif
       {"//foo", "//foo", "."},
       {"//foo/", "//foo/", "."},
-      {"//base", "a", dot_dot_to_root / "../base"},
+#ifdef _WIN32
+      {"//foo", "a", "//foo"},
+      {"//foo/a", "//bar", "//foo/a"},
+      {"//foo/a", "//bar/", "//foo/a"},
+      {"//foo/a", "b", "//foo/a"},
+      {"//foo/a", "/b", "//foo/a"},
+      {"//foo/a", "//bar/b", "//foo/a"},
+      // Using X: instead of C: to avoid influence from the CWD being under C:
+      {"X:/a", "X:/b", "../a"},
+      {"X:/a", "X:b", "X:/a"},
+      {"X:/a", "Y:/a", "X:/a"},
+      {"X:/a", "Y:/b", "X:/a"},
+      {"X:/a", "Y:b", "X:/a"},
+      {"X:a", "X:/b", "X:a"},
+      {"X:a", "X:b", "../a"},
+      {"X:a", "Y:/a", "X:a"},
+      {"X:a", "Y:/b", "X:a"},
+      {"X:a", "Y:b", "X:a"},
+#else
+      {"//foo", "a", dot_dot_to_root / "../foo"},
+      {"//foo/a", "//bar", "../foo/a"},
+      {"//foo/a", "//bar/", "../foo/a"},
+      {"//foo/a", "b", dot_dot_to_root / "../foo/a"},
+      {"//foo/a", "/b", "../foo/a"},
+      {"//foo/a", "//bar/b", "../../foo/a"},
+      {"X:/a", "X:/b", "../a"},
+      {"X:/a", "X:b", "../X:/a"},
+      {"X:/a", "Y:/a", "../../X:/a"},
+      {"X:/a", "Y:/b", "../../X:/a"},
+      {"X:/a", "Y:b", "../X:/a"},
+      {"X:a", "X:/b", "../../X:a"},
+      {"X:a", "X:b", "../X:a"},
+      {"X:a", "Y:/a", "../../X:a"},
+      {"X:a", "Y:/b", "../../X:a"},
+      {"X:a", "Y:b", "../X:a"},
+#endif
       {"a", "a", "."},
       {"a/b", "a/b", "."},
       {"a/b/c/", "a/b/c/", "."},
       {"//foo/a/b", "//foo/a/b", "."},
       {"/a/d", "/a/b/c", "../../d"},
       {"/a/b/c", "/a/d", "../b/c"},
       {"a/b/c", "a", "b/c"},
       {"a/b/c", "a/b/c/x/y", "../.."},
       {"a/b/c", "a/b/c", "."},
       {"a/b", "c/d", "../../a/b"}
   };
   // clang-format on
   int ID = 0;
   for (auto& TC : TestCases) {
     ++ID;
     std::error_code ec = GetTestEC();
-    fs::path p(TC.input);
+    fs::path p = TC.input;
     const fs::path output = fs::proximate(p, TC.base, ec);
+    fs::path expect = TC.expect;
+    expect.make_preferred();
     if (ec) {
       TEST_CHECK(!ec);
       std::fprintf(stderr, "TEST CASE #%d FAILED:\n"
                   "  Input: '%s'\n"
                   "  Base: '%s'\n"
                   "  Expected: '%s'\n",
         ID, TC.input.string().c_str(), TC.base.string().c_str(),
-        TC.expect.string().c_str());
-    } else if (!PathEq(output, TC.expect)) {
-      TEST_CHECK(PathEq(output, TC.expect));
+        expect.string().c_str());
+    } else if (!PathEq(output, expect)) {
+      TEST_CHECK(PathEq(output, expect));
 
       const path canon_input = fs::weakly_canonical(TC.input);
       const path canon_base = fs::weakly_canonical(TC.base);
       const path lexically_p = canon_input.lexically_proximate(canon_base);
       std::fprintf(stderr, "TEST CASE #%d FAILED:\n"
                   "  Input: '%s'\n"
                   "  Base: '%s'\n"
                   "  Expected: '%s'\n"
                   "  Output: '%s'\n"
                   "  Lex Prox: '%s'\n"
                   "  Canon Input: '%s'\n"
                   "  Canon Base: '%s'\n",
         ID, TC.input.string().c_str(), TC.base.string().c_str(),
-        TC.expect.string().c_str(), output.string().c_str(),
+        expect.string().c_str(), output.string().c_str(),
         lexically_p.string().c_str(), canon_input.string().c_str(),
         canon_base.string().c_str());
     }
   }
 }
 
 TEST_SUITE_END()