Add support for nicer error output (#7425)

Fixes #7368
Fixes #7410

This adds some basic support for output styling on Mac and Linux. The formatter does some basic error message parsing because passing them forward in a structured form would be a bigger change.

Author: ilevkivskyi

mypy/main.py

@@ -63,12 +63,15 @@ def main(script_path: Optional[str],
                                        fscache=fscache)
 
     messages = []
+    formatter = util.FancyFormatter(stdout, stderr, options.show_error_codes)
 
     def flush_errors(new_messages: List[str], serious: bool) -> None:
         messages.extend(new_messages)
         f = stderr if serious else stdout
         try:
             for msg in new_messages:
+                if options.color_output:
+                    msg = formatter.colorize(msg)
                 f.write(msg + '\n')
             f.flush()
         except BrokenPipeError:
@@ -105,6 +108,14 @@ def flush_errors(new_messages: List[str], serious: bool) -> None:
     code = 0
     if messages:
         code = 2 if blockers else 1
+    if options.error_summary:
+        if messages:
+            n_errors, n_files = util.count_stats(messages)
+            if n_errors:
+                stdout.write(formatter.format_error(n_errors, n_files, len(sources)) + '\n')
+        else:
+            stdout.write(formatter.format_success(len(sources)) + '\n')
+        stdout.flush()
     if options.fast_exit:
         # Exit without freeing objects -- it's faster.
         #
@@ -568,6 +579,12 @@ def add_invertible_flag(flag: str,
     add_invertible_flag('--show-error-codes', default=False,
                         help="Show error codes in error messages",
                         group=error_group)
+    add_invertible_flag('--no-color-output', dest='color_output', default=True,
+                        help="Do not colorize error messages",
+                        group=error_group)
+    add_invertible_flag('--no-error-summary', dest='error_summary', default=True,
+                        help="Do not show error stats summary",
+                        group=error_group)
 
     strict_help = "Strict mode; enables the following flags: {}".format(
         ", ".join(strict_flag_names))

mypy/options.py

@@ -138,6 +138,10 @@ def __init__(self) -> None:
         # Show "note: In function "foo":" messages.
         self.show_error_context = False
 
+        # Use nicer output (when possible).
+        self.color_output = True
+        self.error_summary = True
+
         # Files in which to allow strict-Optional related errors
         # TODO: Kill this in favor of show_none_errors
         self.strict_optional_whitelist = None   # type: Optional[List[str]]

mypy/test/helpers.py

@@ -387,6 +387,7 @@ def parse_options(program_text: str, testcase: DataDrivenTestCase,
         options = Options()
         # TODO: Enable strict optional in test cases by default (requires *many* test case changes)
         options.strict_optional = False
+        options.error_summary = False
 
     # Allow custom python version to override testcase_pyversion
     if (not flag_list or

mypy/test/testcmdline.py

@@ -47,6 +47,8 @@ def test_python_cmdline(testcase: DataDrivenTestCase, step: int) -> None:
     args = parse_args(testcase.input[0])
     args.append('--show-traceback')
     args.append('--no-site-packages')
+    if '--error-summary' not in args:
+        args.append('--no-error-summary')
     # Type check the program.
     fixed = [python3_path, '-m', 'mypy']
     env = os.environ.copy()

mypy/test/testpep561.py

@@ -114,6 +114,7 @@ def check_mypy_run(self,
             old_dir = os.getcwd()
             os.chdir(venv_dir)
         try:
+            cmd_line.append('--no-error-summary')
             if python_executable != sys.executable:
                 cmd_line.append('--python-executable={}'.format(python_executable))
             out, err, returncode = mypy.api.run(cmd_line)

mypy/test/testpythoneval.py

@@ -57,6 +57,7 @@ def test_python_evaluation(testcase: DataDrivenTestCase, cache_dir: str) -> None
         '--no-site-packages',
         '--no-strict-optional',
         '--no-silence-site-packages',
+        '--no-error-summary',
     ]
     py2 = testcase.name.lower().endswith('python2')
     if py2:

mypy/util.py

@@ -5,8 +5,15 @@
 import subprocess
 import sys
 
-from typing import TypeVar, List, Tuple, Optional, Dict, Sequence, Iterable, Container
-from typing_extensions import Final, Type
+from typing import TypeVar, List, Tuple, Optional, Dict, Sequence, Iterable, Container, IO
+from typing_extensions import Final, Type, Literal
+
+try:
+    import curses
+    import _curses  # noqa
+    CURSES_ENABLED = True
+except ImportError:
+    CURSES_ENABLED = False
 
 T = TypeVar('T')
 
@@ -313,3 +320,121 @@ def check_python_version(program: str) -> None:
     if sys.version_info[:3] == (3, 5, 0):
         sys.exit("Running {name} with Python 3.5.0 is not supported; "
                  "please upgrade to 3.5.1 or newer".format(name=program))
+
+
+def count_stats(errors: List[str]) -> Tuple[int, int]:
+    """Count total number of errors and files in error list."""
+    errors = [e for e in errors if ': error:' in e]
+    files = {e.split(':')[0] for e in errors}
+    return len(errors), len(files)
+
+
+class FancyFormatter:
+    """Apply color and bold font to terminal output.
+
+    This currently only works on Linux and Mac.
+    """
+    def __init__(self, f_out: IO[str], f_err: IO[str],
+                 show_error_codes: bool) -> None:
+        self.show_error_codes = show_error_codes
+        # Check if we are in a human-facing terminal on a supported platform.
+        if sys.platform not in ('linux', 'darwin'):
+            self.dummy_term = True
+            return
+        force_color = int(os.getenv('MYPY_FORCE_COLOR', '0'))
+        if not force_color and (not f_out.isatty() or not f_err.isatty()):
+            self.dummy_term = True
+            return
+
+        # We in a human-facing terminal, check if it supports enough styling.
+        if not CURSES_ENABLED:
+            self.dummy_term = True
+            return
+        try:
+            curses.setupterm()
+        except curses.error:
+            # Most likely terminfo not found.
+            self.dummy_term = True
+            return
+        bold = curses.tigetstr('bold')
+        under = curses.tigetstr('smul')
+        set_color = curses.tigetstr('setaf')
+        self.dummy_term = not (bold and under and set_color)
+        if self.dummy_term:
+            return
+
+        self.BOLD = bold.decode()
+        self.UNDER = under.decode()
+        self.BLUE = curses.tparm(set_color, curses.COLOR_BLUE).decode()
+        self.GREEN = curses.tparm(set_color, curses.COLOR_GREEN).decode()
+        self.RED = curses.tparm(set_color, curses.COLOR_RED).decode()
+        self.YELLOW = curses.tparm(set_color, curses.COLOR_YELLOW).decode()
+        self.NORMAL = curses.tigetstr('sgr0').decode()
+        self.colors = {'red': self.RED, 'green': self.GREEN,
+                       'blue': self.BLUE, 'yellow': self.YELLOW,
+                       'none': ''}
+
+    def style(self, text: str, color: Literal['red', 'green', 'blue', 'yellow', 'none'],
+              bold: bool = False, underline: bool = False) -> str:
+        if self.dummy_term:
+            return text
+        if bold:
+            start = self.BOLD
+        else:
+            start = ''
+        if underline:
+            start += self.UNDER
+        return start + self.colors[color] + text + self.NORMAL
+
+    def colorize(self, error: str) -> str:
+        """Colorize an output line by highlighting the status and error code."""
+        if ': error:' in error:
+            loc, msg = error.split('error:', maxsplit=1)
+            if not self.show_error_codes:
+                return (loc + self.style('error:', 'red', bold=True) +
+                        self.highlight_quote_groups(msg))
+            codepos = msg.rfind('[')
+            code = msg[codepos:]
+            msg = msg[:codepos]
+            return (loc + self.style('error:', 'red', bold=True) +
+                    self.highlight_quote_groups(msg) + self.style(code, 'yellow'))
+        elif ': note:' in error:
+            loc, msg = error.split('note:', maxsplit=1)
+            return loc + self.style('note:', 'blue') + self.underline_link(msg)
+        else:
+            return error
+
+    def highlight_quote_groups(self, msg: str) -> str:
+        if msg.count('"') % 2:
+            # Broken error message, don't do any formatting.
+            return msg
+        parts = msg.split('"')
+        out = ''
+        for i, part in enumerate(parts):
+            if i % 2 == 0:
+                out += self.style(part, 'none')
+            else:
+                out += self.style('"' + part + '"', 'none', bold=True)
+        return out
+
+    def underline_link(self, note: str) -> str:
+        match = re.search(r'https?://\S*', note)
+        if not match:
+            return note
+        start = match.start()
+        end = match.end()
+        return (note[:start] +
+                self.style(note[start:end], 'none', underline=True) +
+                note[end:])
+
+    def format_success(self, n_sources: int) -> str:
+        return self.style('Success: no issues found in {}'
+                          ' source file{}'.format(n_sources, 's' if n_sources != 1 else ''),
+                          'green', bold=True)
+
+    def format_error(self, n_errors: int, n_files: int, n_sources: int) -> str:
+        msg = 'Found {} error{} in {} file{}' \
+              ' (checked {} source file{})'.format(n_errors, 's' if n_errors != 1 else '',
+                                                   n_files, 's' if n_files != 1 else '',
+                                                   n_sources, 's' if n_sources != 1 else '')
+        return self.style(msg, 'red', bold=True)

test-data/unit/cmdline.test

@@ -1322,7 +1322,6 @@ fail
 a/b.py:1: error: Name 'fail' is not defined
 c.py:1: error: Name 'fail' is not defined
 
-
 [case testIniFilesCmdlineOverridesConfig]
 # cmd: mypy override.py
 [file mypy.ini]
@@ -1331,3 +1330,60 @@ files = config.py
 [out]
 mypy: can't read file 'override.py': No such file or directory
 == Return code: 2
+
+[case testErrorSummaryOnSuccess]
+# cmd: mypy --error-summary good.py
+[file good.py]
+x = 2 + 2
+[out]
+Success: no issues found in 1 source file
+== Return code: 0
+
+[case testErrorSummaryOnFail]
+# cmd: mypy --error-summary bad.py
+[file bad.py]
+42 + 'no'
+[out]
+bad.py:1: error: Unsupported operand types for + ("int" and "str")
+Found 1 error in 1 file (checked 1 source file)
+
+[case testErrorSummaryOnFailNotes]
+# cmd: mypy --error-summary bad.py
+[file bad.py]
+from typing import List
+x = []  # type: List[float]
+y = []  # type: List[int]
+x = y
+[out]
+bad.py:4: error: Incompatible types in assignment (expression has type "List[int]", variable has type "List[float]")
+bad.py:4: note: "List" is invariant -- see http://mypy.readthedocs.io/en/latest/common_issues.html#variance
+bad.py:4: note: Consider using "Sequence" instead, which is covariant
+Found 1 error in 1 file (checked 1 source file)
+
+[case testErrorSummaryOnFailTwoErrors]
+# cmd: mypy --error-summary bad.py foo.py
+[file bad.py]
+42 + 'no'
+42 + 'no'
+[file foo.py]
+[out]
+bad.py:1: error: Unsupported operand types for + ("int" and "str")
+bad.py:2: error: Unsupported operand types for + ("int" and "str")
+Found 2 errors in 1 file (checked 2 source files)
+
+[case testErrorSummaryOnFailTwoFiles]
+# cmd: mypy --error-summary bad.py bad2.py
+[file bad.py]
+42 + 'no'
+[file bad2.py]
+42 + 'no'
+[out]
+bad2.py:1: error: Unsupported operand types for + ("int" and "str")
+bad.py:1: error: Unsupported operand types for + ("int" and "str")
+Found 2 errors in 2 files (checked 2 source files)
+
+[case testErrorSummaryOnBadUsage]
+# cmd: mypy --error-summary missing.py
+[out]
+mypy: can't read file 'missing.py': No such file or directory
+== Return code: 2

test-data/unit/daemon.test

@@ -146,6 +146,7 @@ Daemon stopped
 $ {python} -c "print('x=1')" >foo.py
 $ {python} -c "print('x=1')" >bar.py
 $ mypy --local-partial-types --cache-fine-grained --follow-imports=error --no-sqlite-cache --python-version=3.6 -- foo.py bar.py
+Success: no issues found in 2 source files
 $ {python} -c "import shutil; shutil.copy('.mypy_cache/3.6/bar.meta.json', 'asdf.json')"
 -- update bar's timestamp but don't change the file
 $ {python} -c "import time;time.sleep(1)"