[CommandLine] Improve help text for cl::values style options

In order to make an option value truly optional, both the ValueOptional
and an empty-named value are required. This empty-named value appears in
the command-line help text, which is not ideal.

This change improves the help text for these sort of options in a number
of ways:
1) ValueOptional options with an empty-named value now print their help
text twice: both without and then with '=<value>' after the name. The
latter version then lists the allowed values after it.
2) Empty-named values with no help text in ValueOptional options are not
listed in the permitted values.
3) Otherwise empty-named options are printed as =<empty> rather than
simply '='.
4) Option values without help text do not have the '-' separator
printed.

It also tweaks the llvm-symbolizer -functions help text to not print a
trailing ':' as that looks bad combined with 1) above.

Reviewed by: thopre, ruiu

Differential Revision: https://reviews.llvm.org/D57030

llvm-svn: 352750

1 files changed, 27 insertions, 5 deletions

diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index f8bc6a8f615..886595e30a5 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -1663,13 +1663,35 @@ size_t generic_parser_base::getOptionWidth(const Option &O) const {
 void generic_parser_base::printOptionInfo(const Option &O,
                                           size_t GlobalWidth) const {
   if (O.hasArgStr()) {
-    outs() << "  -" << O.ArgStr;
-    Option::printHelpStr(O.HelpStr, GlobalWidth, O.ArgStr.size() + 6);
+    // When the value is optional, first print a line just describing the option
+    // without values.
+    if (O.getValueExpectedFlag() == ValueOptional) {
+      for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
+        if (getOption(i).empty()) {
+          outs() << "  -" << O.ArgStr;
+          Option::printHelpStr(O.HelpStr, GlobalWidth, O.ArgStr.size() + 6);
+          break;
+        }
+      }
+    }
 
+    outs() << "  -" << O.ArgStr << "=<value>";
+    Option::printHelpStr(O.HelpStr, GlobalWidth, O.ArgStr.size() + 14);
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
-      size_t NumSpaces = GlobalWidth - getOption(i).size() - 8;
-      outs() << "    =" << getOption(i);
-      outs().indent(NumSpaces) << " -   " << getDescription(i) << '\n';
+      StringRef ValueName = getOption(i);
+      StringRef Description = getDescription(i);
+      if (O.getValueExpectedFlag() == ValueOptional && ValueName.empty() &&
+          Description.empty())
+        continue;
+      size_t NumSpaces = GlobalWidth - ValueName.size() - 8;
+      outs() << "    =" << ValueName;
+      if (ValueName.empty()) {
+        outs() << "<empty>";
+        NumSpaces -= 7;
+      }
+      if (!Description.empty())
+        outs().indent(NumSpaces) << " -   " << Description;
+      outs() << '\n';
     }
   } else {
     if (!O.HelpStr.empty())