Implement filesystem NB comments, relative paths, and related issues.

This is a fairly large patch that implements all of the filesystem NB comments
and the relative paths changes (ex. adding weakly_canonical). These issues
and papers are all interrelated so their implementation couldn't be split up
nicely.

This patch upgrades <experimental/filesystem> to match the C++17 spec and not
the published experimental TS spec. Some of the changes in this patch are both
API and ABI breaking, however libc++ makes no guarantee about stability for
experimental implementations.

The major changes in this patch are:

* Implement NB comments for filesystem (P0492R2), including:
  * Implement `perm_options` enum as part of NB comments, and update the
    `permissions` function to match.
  * Implement changes to `remove_filename` and `replace_filename`
  * Implement changes to `path::stem()` and `path::extension()` which support
    splitting examples like `.profile`.
  * Change path iteration to return an empty path instead of '.' for trailing
    separators.
  * Change `operator/=` to handle absolute paths on the RHS.
  * Change `absolute` to no longer accept a current path argument.

* Implement relative paths according to NB comments (P0219r1)

* Combine `path.cpp` and `operations.cpp` since some path functions require
  access to the operations internals, and some fs operations require access
  to the path parser.

llvm-svn: 329028

1 files changed, 17 insertions, 76 deletions

diff --git a/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.absolute/absolute.pass.cpp b/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.absolute/absolute.pass.cpp
index 97d168a4a53..9b73aedc8ef 100644
--- a/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.absolute/absolute.pass.cpp
+++ b/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.absolute/absolute.pass.cpp
@@ -28,89 +28,30 @@ TEST_SUITE(filesystem_absolute_path_test_suite)
 TEST_CASE(absolute_signature_test)
 {
     const path p; ((void)p);
+    std::error_code ec;
     ASSERT_NOT_NOEXCEPT(absolute(p));
-    ASSERT_NOT_NOEXCEPT(absolute(p, p));
+    ASSERT_NOT_NOEXCEPT(absolute(p, ec));
 }
 
-// There are 4 cases is the proposal for absolute path.
-// Each scope tests one of the cases.
-TEST_CASE(absolute_path_test)
-{
-    // has_root_name() && has_root_directory()
-    {
-        const path p("//net/foo");
-        const path base("//net/bar/baz");
-        TEST_REQUIRE(p.has_root_name());
-        TEST_REQUIRE(p.has_root_directory());
-        TEST_CHECK(p.is_absolute());
-        path ret = absolute(p, base);
-        TEST_CHECK(ret.is_absolute());
-        TEST_CHECK(ret == p);
-    }
-    // !has_root_name() && has_root_directory()
-    {
-        const path p("/foo");
-        const path base("//net/bar");
-        TEST_REQUIRE(not p.has_root_name());
-        TEST_REQUIRE(p.has_root_directory());
-        TEST_CHECK(p.is_absolute());
-        // ensure absolute(base) is not recursively called
-        TEST_REQUIRE(base.has_root_name());
-        TEST_REQUIRE(base.has_root_directory());
-
-        path ret = absolute(p, base);
-        TEST_CHECK(ret.is_absolute());
-        TEST_CHECK(ret.has_root_name());
-        TEST_CHECK(ret.root_name() == path("//net"));
-        TEST_CHECK(ret.has_root_directory());
-        TEST_CHECK(ret.root_directory() == path("/"));
-        TEST_CHECK(ret == path("//net/foo"));
-    }
-    // has_root_name() && !has_root_directory()
-    {
-        const path p("//net");
-        const path base("//net/foo/bar");
-        TEST_REQUIRE(p.has_root_name());
-        TEST_REQUIRE(not p.has_root_directory());
-        TEST_CHECK(not p.is_absolute());
-        // absolute is called recursively on base. The following conditions
-        // must be true for it to return base unmodified
-        TEST_REQUIRE(base.has_root_name());
-        TEST_REQUIRE(base.has_root_directory());
-        path ret = absolute(p, base);
-        const path expect("//net/foo/bar");
-        TEST_CHECK(ret.is_absolute());
-        TEST_CHECK(ret == path("//net/foo/bar"));
-    }
-    // !has_root_name() && !has_root_directory()
-    {
-        const path p("bar/baz");
-        const path base("//net/foo");
-        TEST_REQUIRE(not p.has_root_name());
-        TEST_REQUIRE(not p.has_root_directory());
-        TEST_REQUIRE(base.has_root_name());
-        TEST_REQUIRE(base.has_root_directory());
-
-        path ret = absolute(p, base);
-        TEST_CHECK(ret.is_absolute());
-        TEST_CHECK(ret == path("//net/foo/bar/baz"));
-    }
-}
 
-TEST_CASE(absolute_path_with_default_base)
+TEST_CASE(basic_test)
 {
-    const path testCases[] = {
-        "//net/foo", //  has_root_name() &&  has_root_directory()
-        "/foo",      // !has_root_name() &&  has_root_directory()
-        "//net",     //  has_root_name() && !has_root_directory()
-        "bar/baz"    // !has_root_name() && !has_root_directory()
+    const fs::path cwd = fs::current_path();
+    const struct {
+      std::string input;
+      std::string expect;
+    } TestCases [] = {
+        {"", cwd / ""},
+        {"foo", cwd / "foo"},
+        {"foo/", cwd / "foo/"},
+        {"/already_absolute", "/already_absolute"}
     };
-    const path base = current_path();
-    for (auto& p : testCases) {
-        const path ret = absolute(p);
-        const path expect = absolute(p, base);
+    for (auto& TC : TestCases) {
+        std::error_code ec = GetTestEC();
+        const path ret = absolute(TC.input, ec);
+        TEST_CHECK(!ec);
         TEST_CHECK(ret.is_absolute());
-        TEST_CHECK(ret == expect);
+        TEST_CHECK(PathEq(ret, TC.expect));
     }
 }