[lldb] Add support for escaping fish arguments

[teemperor]

Summary

LLDB supports having globbing regexes in the process launch arguments that will be resolved
using the user's shell. This requires that we pass the launch args to the shell and then read
back the expanded arguments using LLDB's argdumper utility.

As the shell will not just expand the globbing regexes but all special characters, we need to
escape all non-globbing charcters such as $, &, <, >, etc. as those otherwise are interpreted and
removed in the step where we expand the globbing characters. Also because the special characters
are shell-specific, LLDB needs to maintain a list of all the characters that need to be escaped for
each specific shell.

This patch adds the list of special characters that need to be escaped for fish. Without this patch
on systems where fish is the user's shell having any of these special characters in your arguments or path to
the binary will cause the process launch to fail. E.g., lldb -- ./calc 1<2 is failing without this patch.
The same happens if the absolute path to calc is in a directory that contains for example parentheses
or other special characters.

[teemperor]

• Add pipe and backslash also as special characters.

[JDevlieghere]

lldb/source/Utility/Args.cpp

387

I guess this should be fish?

[teemperor]

Whoops, wrong diff...

[teemperor]

• Upload the fish diff

[JDevlieghere]

LGTM

lldb/source/Utility/Args.cpp

 
 std::string Args::GetShellSafeArgument(const FileSpec &shell,
                                        llvm::StringRef unsafe_arg) {
   struct ShellDescriptor {
     ConstString m_basename;
     llvm::StringRef m_escapables;
   };
 
   static ShellDescriptor g_Shells[] = {{ConstString("bash"), " '\"<>()&;"},
+                                       {ConstString("fish"), " '\"<>()&\\|;"},
                                        {ConstString("tcsh"), " '\"<>()&;"},
                                        {ConstString("zsh"), " '\"<>()&;\\|"},
                                        {ConstString("sh"), " '\"<>()&;"}};
 
   // safe minimal set
   llvm::StringRef escapables = " '\"";
 
   if (auto basename = shell.GetFilename()) {

lldb/unittests/Utility/ArgsTest.cpp

TEST(ArgsTest, GetShellSafeArgument) {
 
   // Test escaping sh special characters.
   FileSpec sh("/bin/sh", FileSpec::Style::posix);
   EXPECT_EQ(Args::GetShellSafeArgument(sh, R"( '"<>()&;)"),
             R"(\ \'\"\<\>\(\)\&\;)");
   // Normal characters and globbing expressions that shouldn't be escaped.
   EXPECT_EQ(Args::GetShellSafeArgument(sh, "aA$1*"), "aA$1*");
 
+  // Test escaping fish special characters.
+  FileSpec fish("/bin/fish", FileSpec::Style::posix);
+  EXPECT_EQ(Args::GetShellSafeArgument(fish, R"( '"<>()&\|;)"),
+            R"(\ \'\"\<\>\(\)\&\\\|\;)");
+  // Normal characters and expressions that shouldn't be escaped.
+  EXPECT_EQ(Args::GetShellSafeArgument(fish, "aA$1*"), "aA$1*");
+
   // Try escaping with an unknown shell.
   FileSpec unknown_shell("/bin/unknown_shell", FileSpec::Style::posix);
   EXPECT_EQ(Args::GetShellSafeArgument(unknown_shell, "a'b"), "a\\'b");
   EXPECT_EQ(Args::GetShellSafeArgument(unknown_shell, "a\"b"), "a\\\"b");
 }