Simpler/cleaner reveal_type() (#20929)

As discussed with @JukkaL, I only select most important things, but make
the new behavior default. I will make the bulk of test output updates in
a separate PR, here I only update tests where it is easier to update
them, than to postpone.

Three main changes here:
* Strip `builtins.` prefix everywhere.
* Simpler type variables (no ids, no repeated defaults).
* Cleaned-up, fixed, and unified handling on `Unpack[...]`.

Few smaller notes:
* In some cases we ignored `options` when formatting types (esp. in
tests).
* There is a bunch of code duplication, but it looks hard to fix, so I
don't.
* Single quotes for TypedDict names are redundant (just add to visual
noise), so I remove them as well.

Author: ilevkivskyi

mypy/messages.py

@@ -2970,11 +2970,20 @@ def [T <: int] f(self, x: int, y: T) -> None
         if tp.arg_kinds[i] == ARG_STAR2:
             s += "**"
         name = tp.arg_names[i]
+        if not name and not options.reveal_verbose_types:
+            # Avoid ambiguous (and weird) formatting for anonymous args/kwargs.
+            if tp.arg_kinds[i] == ARG_STAR and isinstance(tp.arg_types[i], UnpackType):
+                name = "args"
+            elif tp.arg_kinds[i] == ARG_STAR2 and tp.unpack_kwargs:
+                name = "kwargs"
         if name:
             s += name + ": "
         type_str = format_type_bare(tp.arg_types[i], options)
         if tp.arg_kinds[i] == ARG_STAR2 and tp.unpack_kwargs:
-            type_str = f"Unpack[{type_str}]"
+            if options.reveal_verbose_types:
+                type_str = f"Unpack[{type_str}]"
+            else:
+                type_str = f"**{type_str}"
         s += type_str
         if tp.arg_kinds[i].is_optional():
             s += " = ..."

mypy/options.py

@@ -372,6 +372,8 @@ def __init__(self) -> None:
         self.show_error_end: bool = False
         self.hide_error_codes = False
         self.show_error_code_links = False
+        # This is an internal-only flag to simplify migrating test output.
+        self.reveal_verbose_types = False
         # Use soft word wrap and show trimmed source snippets with error location markers.
         self.pretty = False
         self.dump_graph = False
@@ -433,7 +435,7 @@ def __init__(self) -> None:
         self.mypyc_skip_c_generation = False
 
     def use_star_unpack(self) -> bool:
-        return self.python_version >= (3, 11)
+        return self.python_version >= (3, 11) or not self.reveal_verbose_types
 
     def snapshot(self) -> dict[str, object]:
         """Produce a comparable snapshot of this Option"""

mypy/semanal.py

@@ -292,6 +292,7 @@
     TypeAliasType,
     TypedDictType,
     TypeOfAny,
+    TypeStrVisitor,
     TypeType,
     TypeVarId,
     TypeVarLikeType,
@@ -1387,7 +1388,7 @@ def process_deprecated_overload(self, defn: OverloadedFuncDef) -> None:
                     elif (deprecated := self.get_deprecated(d)) is not None:
                         deprecation = True
                         if isinstance(typ := item.func.type, CallableType):
-                            typestr = f" {typ} "
+                            typestr = f" {typ.accept(TypeStrVisitor(options=self.options))} "
                         else:
                             typestr = " "
                         item.func.deprecated = (

mypy/test/testcheck.py

@@ -137,6 +137,7 @@ def run_case_once(
         options.use_builtins_fixtures = True
         options.show_traceback = True
         options.native_parser = bool(os.environ.get("TEST_NATIVE_PARSER"))
+        options.reveal_verbose_types = not testcase.name.endswith("_no_verbose_reveal")
 
         if options.num_workers:
             options.fixed_format_cache = True

mypy/test/testfinegrained.py

@@ -155,6 +155,7 @@ def get_options(self, source: str, testcase: DataDrivenTestCase, build_cache: bo
         options.export_types = "inspect" in testcase.file
         # Treat empty bodies safely for these test cases.
         options.allow_empty_bodies = not testcase.name.endswith("_no_empty")
+        options.reveal_verbose_types = True
         if re.search("flags:.*--follow-imports", source) is None:
             # Override the default for follow_imports
             options.follow_imports = "error"

mypy/test/testmerge.py

@@ -102,6 +102,7 @@ def build(self, source: str, testcase: DataDrivenTestCase) -> BuildResult | None
         options.export_types = True
         options.show_traceback = True
         options.allow_empty_bodies = True
+        options.reveal_verbose_types = True
         main_path = os.path.join(test_temp_dir, "main")
 
         self.str_conv.options = options
@@ -222,7 +223,8 @@ def dump_types(
                     key=lambda n: (
                         n.line,
                         short_type(n),
-                        n.str_with_options(self.str_conv.options) + str(type_map[n]),
+                        n.str_with_options(self.str_conv.options)
+                        + type_map[n].accept(self.type_str_conv),
                     ),
                 ):
                     typ = type_map[expr]

mypy/test/testsemanal.py

@@ -8,6 +8,7 @@
 from mypy.modulefinder import BuildSource
 from mypy.nodes import TypeInfo
 from mypy.options import Options
+from mypy.strconv import StrConv
 from mypy.test.config import test_temp_dir
 from mypy.test.data import DataDrivenTestCase, DataSuite
 from mypy.test.helpers import (
@@ -19,8 +20,9 @@
 )
 
 # Semantic analyzer test cases: dump parse tree
-
 # Semantic analysis test case description files.
+from mypy.types import TypeStrVisitor
+
 semanal_files = find_test_files(
     pattern="semanal-*.test",
     exclude=[
@@ -38,6 +40,7 @@ def get_semanal_options(program_text: str, testcase: DataDrivenTestCase) -> Opti
     options.semantic_analysis_only = True
     options.show_traceback = True
     options.python_version = PYTHON3_VERSION
+    options.reveal_verbose_types = True
     return options
 
 
@@ -154,14 +157,22 @@ class SemAnalTypeInfoSuite(DataSuite):
     required_out_section = True
     files = ["semanal-typeinfo.test"]
 
+    def setup(self) -> None:
+        super().setup()
+        self.str_conv = StrConv(options=Options())
+        self.type_str_conv = TypeStrVisitor(options=Options())
+
     def run_case(self, testcase: DataDrivenTestCase) -> None:
         """Perform a test case."""
+        src = "\n".join(testcase.input)
+        options = get_semanal_options(src, testcase)
+        self.str_conv.options = options
+        self.type_str_conv.options = options
         try:
             # Build test case input.
-            src = "\n".join(testcase.input)
             result = build.build(
                 sources=[BuildSource("main", None, src)],
-                options=get_semanal_options(src, testcase),
+                options=options,
                 alt_lib_path=test_temp_dir,
             )
             a = result.errors
@@ -179,7 +190,7 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
                                 typeinfos[n.fullname] = n.node
 
             # The output is the symbol table converted into a string.
-            a = str(typeinfos).split("\n")
+            a = typeinfos.dump(self.str_conv, self.type_str_conv).split("\n")
         except CompileError as e:
             a = e.messages
         assert_string_arrays_equal(
@@ -190,10 +201,10 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
 
 
 class TypeInfoMap(dict[str, TypeInfo]):
-    def __str__(self) -> str:
+    def dump(self, str_conv: StrConv, type_str_conv: TypeStrVisitor) -> str:
         a: list[str] = ["TypeInfoMap("]
         for x, y in sorted(self.items()):
-            ti = ("\n" + "  ").join(str(y).split("\n"))
+            ti = ("\n" + "  ").join(y.dump(str_conv, type_str_conv).split("\n"))
             a.append(f"  {x} : {ti}")
         a[-1] += ")"
         return "\n".join(a)

mypy/test/teststubtest.py

@@ -2799,7 +2799,7 @@ def test_output(self) -> None:
             f'error: {TEST_MODULE_NAME}.bad is inconsistent, stub parameter "number" differs '
             'from runtime parameter "num"\n'
             f"Stub: in file {TEST_MODULE_NAME}.pyi:1\n"
-            "def (number: builtins.int, text: builtins.str)\n"
+            "def (number: int, text: str)\n"
             f"Runtime: in file {TEST_MODULE_NAME}.py:1\ndef (num, text)\n\n"
             "Found 1 error (checked 1 module)\n"
         )
@@ -2994,7 +2994,7 @@ def myfunction(arg: str, /) -> None: ...
         stub = result.files["__main__"].names["myfunction"].node
         assert isinstance(stub, nodes.OverloadedFuncDef)
         sig = mypy.stubtest.Signature.from_overloadedfuncdef(stub)
-        assert str(sig) == "def (arg: builtins.int | builtins.str)"
+        assert str(sig) == "def (arg: int | str)"
 
     def test_config_file(self) -> None:
         runtime = "temp = 5\n"

mypy/test/testtransform.py

@@ -38,6 +38,7 @@ def test_transform(testcase: DataDrivenTestCase) -> None:
         options.use_builtins_fixtures = True
         options.semantic_analysis_only = True
         options.show_traceback = True
+        options.reveal_verbose_types = True
         result = build.build(
             sources=[BuildSource("main", None, src)], options=options, alt_lib_path=test_temp_dir
         )

mypy/test/testtypegen.py

@@ -35,6 +35,7 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
             options.export_types = True
             options.preserve_asts = True
             options.allow_empty_bodies = True
+            options.reveal_verbose_types = True
             result = build.build(
                 sources=[BuildSource("main", None, src)],
                 options=options,