1 files changed, 90 insertions, 0 deletions
diff --git a/python/mozbuild/mozbuild/configure/help.py b/python/mozbuild/mozbuild/configure/help.py
new file mode 100644
index 0000000000..bfd5e6ad6d
--- /dev/null
+++ b/python/mozbuild/mozbuild/configure/help.py
@@ -0,0 +1,90 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import re
+from collections import defaultdict
+
+from mozbuild.configure.options import Option
+
+
+class HelpFormatter(object):
+    def __init__(self, argv0):
+        self.intro = ["Usage: %s [options]" % os.path.basename(argv0)]
+        self.options = []
+
+    def add(self, option):
+        assert isinstance(option, Option)
+        if option.possible_origins == ("implied",):
+            # Don't display help if our option can only be implied.
+            return
+        self.options.append(option)
+
+    def format_options_by_category(self, options_by_category):
+        ret = []
+        for category, options in sorted(
+            options_by_category.items(), key=lambda x: x[0]
+        ):
+            ret.append("  " + category + ":")
+            for option in sorted(options, key=lambda opt: opt.option):
+                opt = option.option
+                if option.choices:
+                    opt += "={%s}" % ",".join(option.choices)
+                help = self.format_help(option)
+                if len(option.default):
+                    if help:
+                        help += " "
+                    help += "[%s]" % ",".join(option.default)
+
+                if len(opt) > 24 or not help:
+                    ret.append("    %s" % opt)
+                    if help:
+                        ret.append("%s%s" % (" " * 30, help))
+                else:
+                    ret.append("    %-24s  %s" % (opt, help))
+            ret.append("")
+        return ret
+
+    RE_FORMAT = re.compile(r"{([^|}]*)\|([^|}]*)}")
+
+    # Return formatted help text for --{enable,disable,with,without}-* options.
+    #
+    # Format is the following syntax:
+    #   {String for --enable or --with|String for --disable or --without}
+    #
+    # For example, '{Enable|Disable} optimizations' will be formatted to
+    # 'Enable optimizations' if the options's prefix is 'enable' or 'with',
+    # and formatted to 'Disable optimizations' if the options's prefix is
+    # 'disable' or 'without'.
+    def format_help(self, option):
+        if not option.help:
+            return ""
+
+        if option.prefix in ("enable", "with"):
+            replacement = r"\1"
+        elif option.prefix in ("disable", "without"):
+            replacement = r"\2"
+        else:
+            return option.help
+
+        return self.RE_FORMAT.sub(replacement, option.help)
+
+    def usage(self, out):
+        options_by_category = defaultdict(list)
+        env_by_category = defaultdict(list)
+        for option in self.options:
+            target = options_by_category if option.name else env_by_category
+            target[option.category].append(option)
+        options_formatted = [
+            "Options: [defaults in brackets after descriptions]"
+        ] + self.format_options_by_category(options_by_category)
+        env_formatted = ["Environment variables:"] + self.format_options_by_category(
+            env_by_category
+        )
+        print(
+            "\n\n".join(
+                "\n".join(t) for t in (self.intro, options_formatted, env_formatted)
+            ),
+            file=out,
+        )