fix: show custom error message in prompt with hide_input=True

CHANGES.rst

@@ -2,6 +2,10 @@
 
 Unreleased
 
+-   Show custom error messages from types when ``prompt`` with
+    ``hide_input=True`` fails validation, instead of always showing a
+    generic message. Built-in type messages mask the input value.
+    :issue:`2809`
 -   Fix handling of ``flag_value`` when ``is_flag=False`` to allow such options to be
     used without an explicit value. :issue:`3084`
 -   Hide ``Sentinel.UNSET`` values as ``None`` when using ``lookup_default()``.

src/click/termui.py

@@ -178,7 +178,20 @@ def prompt_func(text: str) -> str:
             result = value_proc(value)
         except UsageError as e:
             if hide_input:
-                echo(_("Error: The value you entered was invalid."), err=err)
+                repr_val = repr(value)
+                if repr_val in e.message:
+                    # Built-in type pattern: mask the repr'd value.
+                    msg = e.message.replace(repr_val, "'***'")
+                elif value in e.message:
+                    # Raw value found: could be a coincidental or
+                    # unquoted match. Ambiguous, use generic.
+                    msg = _("The value you entered was invalid.")
+                else:
+                    # Value not found: show as-is, assuming custom
+                    # types with hide_input=True avoid leaking input.
+                    msg = e.message
+
+                echo(_("Error: {msg}").format(msg=msg), err=err)
             else:
                 echo(_("Error: {e.message}").format(e=e), err=err)
             continue

tests/test_termui.py

@@ -710,3 +710,58 @@ def cli(flag):
         assert result.output == expected_output
         assert not result.stderr
         assert result.exit_code == 0 if expected not in (REPEAT, INVALID) else 1
+
+
+class _CustomTypeNoValue(click.ParamType):
+    name = "custom"
+
+    def convert(self, value, param, ctx):
+        if len(value) < 4:
+            self.fail("Password must be at least 4 characters", param, ctx)
+        return value
+
+
+class _CustomTypeWithRawValue(click.ParamType):
+    name = "custom_raw"
+
+    def convert(self, value, param, ctx):
+        if value == "bad":
+            self.fail(f"rejected: {value}", param, ctx)
+        return value
+
+
+@pytest.mark.parametrize(
+    ("type", "expected_fragment", "unexpected_fragment"),
+    [
+        pytest.param(
+            click.INT,
+            "'***' is not a valid integer",
+            "bad",
+            id="builtin-int-masks-repr-value",
+        ),
+        pytest.param(
+            _CustomTypeNoValue(),
+            "Password must be at least 4 characters",
+            None,
+            id="custom-no-value-shows-message",
+        ),
+        pytest.param(
+            _CustomTypeWithRawValue(),
+            "The value you entered was invalid",
+            "bad",
+            id="custom-raw-value-falls-back-to-generic",
+        ),
+    ],
+)
+def test_hide_input_error_message(runner, type, expected_fragment, unexpected_fragment):
+    """https://github.com/pallets/click/issues/2809"""
+
+    @click.command()
+    @click.option("--password", prompt=True, hide_input=True, type=type)
+    def cli(password):
+        click.echo(password)
+
+    result = runner.invoke(cli, input="bad")
+    assert expected_fragment in result.output
+    if unexpected_fragment is not None:
+        assert unexpected_fragment not in result.output