Split generation of option's help extra and rendering

CHANGES.rst

@@ -20,6 +20,9 @@ Unreleased
 -   Improve type hinting for decorators and give all generic types parameters.
     :issue:`2398`
 -   Fix return value and type signature of `shell_completion.add_completion_class` function. :pr:`2421`
+-   Add ``get_help_extra`` method on ``Option`` to fetch the generated extra
+    items used in ``get_help_record`` to render help text. :issue:`2516`
+    :pr:`2517`
 
 
 Version 8.1.3

src/click/core.py

@@ -2737,7 +2737,28 @@ def _write_opts(opts: t.Sequence[str]) -> str:
             rv.append(_write_opts(self.secondary_opts))
 
         help = self.help or ""
-        extra = []
+
+        extra = self.get_help_extra(ctx)
+        extra_items = []
+        if "envvars" in extra:
+            extra_items.append(
+                _("env var: {var}").format(var=", ".join(extra["envvars"]))
+            )
+        if "default" in extra:
+            extra_items.append(_("default: {default}").format(default=extra["default"]))
+        if "range" in extra:
+            extra_items.append(extra["range"])
+        if "required" in extra:
+            extra_items.append(_(extra["required"]))
+
+        if extra_items:
+            extra_str = "; ".join(extra_items)
+            help = f"{help}  [{extra_str}]" if help else f"[{extra_str}]"
+
+        return ("; " if any_prefix_is_slash else " / ").join(rv), help
+
+    def get_help_extra(self, ctx: Context) -> t.Dict[str, t.Any]:
+        extra: t.Dict[str, t.Any] = {}
 
         if self.show_envvar:
             envvar = self.envvar
@@ -2751,12 +2772,10 @@ def _write_opts(opts: t.Sequence[str]) -> str:
                     envvar = f"{ctx.auto_envvar_prefix}_{self.name.upper()}"
 
             if envvar is not None:
-                var_str = (
-                    envvar
-                    if isinstance(envvar, str)
-                    else ", ".join(str(d) for d in envvar)
-                )
-                extra.append(_("env var: {var}").format(var=var_str))
+                if isinstance(envvar, str):
+                    extra["envvars"] = (envvar,)
+                else:
+                    extra["envvars"] = tuple(str(d) for d in envvar)
 
         # Temporarily enable resilient parsing to avoid type casting
         # failing for the default. Might be possible to extend this to
@@ -2799,7 +2818,7 @@ def _write_opts(opts: t.Sequence[str]) -> str:
                 default_string = str(default_value)
 
             if default_string:
-                extra.append(_("default: {default}").format(default=default_string))
+                extra["default"] = default_string
 
         if (
             isinstance(self.type, types._NumberRangeBase)
@@ -2809,16 +2828,12 @@ def _write_opts(opts: t.Sequence[str]) -> str:
             range_str = self.type._describe_range()
 
             if range_str:
-                extra.append(range_str)
+                extra["range"] = range_str
 
         if self.required:
-            extra.append(_("required"))
+            extra["required"] = "required"
 
-        if extra:
-            extra_str = "; ".join(extra)
-            help = f"{help}  [{extra_str}]" if help else f"[{extra_str}]"
-
-        return ("; " if any_prefix_is_slash else " / ").join(rv), help
+        return extra
 
     @t.overload
     def get_default(

tests/test_options.py

@@ -316,6 +316,7 @@ def __str__(self):
 
     opt = click.Option(["-a"], default=Value(), show_default=True)
     ctx = click.Context(click.Command("cli"))
+    assert opt.get_help_extra(ctx) == {"default": "special value"}
     assert "special value" in opt.get_help_record(ctx)[1]
 
 
@@ -331,6 +332,7 @@ def __str__(self):
 def test_intrange_default_help_text(type, expect):
     option = click.Option(["--num"], type=type, show_default=True, default=2)
     context = click.Context(click.Command("test"))
+    assert option.get_help_extra(context) == {"default": "2", "range": expect}
     result = option.get_help_record(context)[1]
     assert expect in result
 
@@ -339,6 +341,7 @@ def test_count_default_type_help():
     """A count option with the default type should not show >=0 in help."""
     option = click.Option(["--count"], count=True, help="some words")
     context = click.Context(click.Command("test"))
+    assert option.get_help_extra(context) == {}
     result = option.get_help_record(context)[1]
     assert result == "some words"
 
@@ -354,6 +357,7 @@ def test_file_type_help_default():
         ["--in"], type=click.File(), default=__file__, show_default=True
     )
     context = click.Context(click.Command("test"))
+    assert option.get_help_extra(context) == {"default": __file__}
     result = option.get_help_record(context)[1]
     assert __file__ in result
 
@@ -741,6 +745,7 @@ def test_show_default_boolean_flag_name(runner, default, expect):
         help="Enable/Disable the cache.",
     )
     ctx = click.Context(click.Command("test"))
+    assert opt.get_help_extra(ctx) == {"default": expect}
     message = opt.get_help_record(ctx)[1]
     assert f"[default: {expect}]" in message
 
@@ -757,6 +762,7 @@ def test_show_true_default_boolean_flag_value(runner):
         help="Enable the cache.",
     )
     ctx = click.Context(click.Command("test"))
+    assert opt.get_help_extra(ctx) == {"default": "True"}
     message = opt.get_help_record(ctx)[1]
     assert "[default: True]" in message
 
@@ -774,6 +780,7 @@ def test_hide_false_default_boolean_flag_value(runner, default):
         help="Enable the cache.",
     )
     ctx = click.Context(click.Command("test"))
+    assert opt.get_help_extra(ctx) == {}
     message = opt.get_help_record(ctx)[1]
     assert "[default: " not in message
 
@@ -782,6 +789,7 @@ def test_show_default_string(runner):
     """When show_default is a string show that value as default."""
     opt = click.Option(["--limit"], show_default="unlimited")
     ctx = click.Context(click.Command("cli"))
+    assert opt.get_help_extra(ctx) == {"default": "(unlimited)"}
     message = opt.get_help_record(ctx)[1]
     assert "[default: (unlimited)]" in message
 
@@ -790,6 +798,7 @@ def test_do_not_show_no_default(runner):
     """When show_default is True and no default is set do not show None."""
     opt = click.Option(["--limit"], show_default=True)
     ctx = click.Context(click.Command("cli"))
+    assert opt.get_help_extra(ctx) == {}
     message = opt.get_help_record(ctx)[1]
     assert "[default: None]" not in message
 
@@ -800,28 +809,30 @@ def test_do_not_show_default_empty_multiple():
     """
     opt = click.Option(["-a"], multiple=True, help="values", show_default=True)
     ctx = click.Context(click.Command("cli"))
+    assert opt.get_help_extra(ctx) == {}
     message = opt.get_help_record(ctx)[1]
     assert message == "values"
 
 
 @pytest.mark.parametrize(
-    ("ctx_value", "opt_value", "expect"),
+    ("ctx_value", "opt_value", "extra_value", "expect"),
     [
-        (None, None, False),
-        (None, False, False),
-        (None, True, True),
-        (False, None, False),
-        (False, False, False),
-        (False, True, True),
-        (True, None, True),
-        (True, False, False),
-        (True, True, True),
-        (False, "one", True),
+        (None, None, {}, False),
+        (None, False, {}, False),
+        (None, True, {"default": "1"}, True),
+        (False, None, {}, False),
+        (False, False, {}, False),
+        (False, True, {"default": "1"}, True),
+        (True, None, {"default": "1"}, True),
+        (True, False, {}, False),
+        (True, True, {"default": "1"}, True),
+        (False, "one", {"default": "(one)"}, True),
     ],
 )
-def test_show_default_precedence(ctx_value, opt_value, expect):
+def test_show_default_precedence(ctx_value, opt_value, extra_value, expect):
     ctx = click.Context(click.Command("test"), show_default=ctx_value)
     opt = click.Option("-a", default=1, help="value", show_default=opt_value)
+    assert opt.get_help_extra(ctx) == extra_value
     help = opt.get_help_record(ctx)[1]
     assert ("default:" in help) is expect