Improve error formatting

Refs   #812.

coconut/compiler/compiler.py

@@ -49,6 +49,7 @@
 )
 
 from coconut.constants import (
+    PY35,
     specific_targets,
     targets,
     pseudo_targets,
@@ -1359,7 +1360,7 @@ def parse(
                         internal_assert(pre_procd is not None, "invalid deferred syntax error in pre-processing", err)
                         raise self.make_syntax_err(err, pre_procd, after_parsing=parsed is not None)
                     # RuntimeError, not RecursionError, for Python < 3.5
-                    except RuntimeError as err:
+                    except (RecursionError if PY35 else RuntimeError) as err:
                         raise CoconutException(
                             str(err), extra="try again with --recursion-limit greater than the current "
                             + str(sys.getrecursionlimit()) + " (you may also need to increase --stack-size)",

coconut/compiler/grammar.py

@@ -2192,7 +2192,7 @@ class Grammar(object):
         where_stmt_ref = where_item + where_suite
 
         implicit_return = (
-            invalid_syntax(return_stmt, "expected expression but got return statement")
+            invalid_syntax(return_stmt, "assignment function expected expression as last statement but got return instead")
             | attach(new_testlist_star_expr, implicit_return_handle)
         )
         implicit_return_where = Forward()

coconut/constants.py

@@ -315,12 +315,11 @@ def get_path_env_var(env_var, default):
 )
 
 tabideal = 4  # spaces to indent code for displaying
-
-taberrfmt = 2  # spaces to indent exceptions
-
 justify_len = 79  # ideal line length
 
+taberrfmt = 2  # spaces to indent exceptions
 min_squiggles_in_err_msg = 1
+max_err_msg_lines = 10
 
 # for pattern-matching
 default_matcher_style = "python warn"
@@ -645,6 +644,8 @@ def get_path_env_var(env_var, default):
 log_color_code = "93"
 
 default_style = "default"
+fake_styles = ("none", "list")
+
 prompt_histfile = get_path_env_var(
     "COCONUT_HISTORY_FILE",
     os.path.join(coconut_home, ".coconut_history"),

coconut/exceptions.py

@@ -30,6 +30,7 @@
     taberrfmt,
     report_this_text,
     min_squiggles_in_err_msg,
+    max_err_msg_lines,
 )
 from coconut.util import (
     pickleable_obj,
@@ -38,6 +39,7 @@
     clean,
     get_displayable_target,
     normalize_newlines,
+    highlight,
 )
 
 # -----------------------------------------------------------------------------------------------------------------------
@@ -153,8 +155,10 @@ def message(self, message, source, point, ln, extra=None, endpoint=None, filenam
                     point_ind = clip(point_ind, 0, len(part))
                     endpoint_ind = clip(endpoint_ind, point_ind, len(part))
 
-                    message += "\n" + " " * taberrfmt + part
+                    # add code to message
+                    message += "\n" + " " * taberrfmt + highlight(part)
 
+                    # add squiggles to message
                     if point_ind > 0 or endpoint_ind > 0:
                         err_len = endpoint_ind - point_ind
                         message += "\n" + " " * (taberrfmt + point_ind)
@@ -182,14 +186,26 @@ def message(self, message, source, point, ln, extra=None, endpoint=None, filenam
 
                     max_line_len = max(len(line) for line in lines)
 
+                    # add top squiggles
                     message += "\n" + " " * (taberrfmt + point_ind)
                     if point_ind >= len(lines[0]):
                         message += "|"
                     else:
                         message += "/" + "~" * (len(lines[0]) - point_ind - 1)
                     message += "~" * (max_line_len - len(lines[0])) + "\n"
-                    for line in lines:
-                        message += "\n" + " " * taberrfmt + line
+
+                    # add code
+                    if len(lines) > max_err_msg_lines:
+                        for i in range(max_err_msg_lines // 2):
+                            message += "\n" + " " * taberrfmt + highlight(lines[i])
+                        message += "\n" + " " * (taberrfmt // 2) + "..."
+                        for i in range(len(lines) - max_err_msg_lines // 2, len(lines)):
+                            message += "\n" + " " * taberrfmt + highlight(lines[i])
+                    else:
+                        for line in lines:
+                            message += "\n" + " " * taberrfmt + highlight(line)
+
+                    # add bottom squiggles
                     message += (
                         "\n\n" + " " * taberrfmt + "~" * endpoint_ind
                         + ("^" if self.point_to_endpoint else "/" if 0 < endpoint_ind < len(lines[-1]) else "|")

coconut/highlighter.py

@@ -19,10 +19,12 @@
 
 from coconut.root import *  # NOQA
 
+from pygments import highlight
 from pygments.lexers import Python3Lexer, PythonConsoleLexer
 from pygments.token import Text, Operator, Keyword, Name, Number
 from pygments.lexer import words, bygroups
 from pygments.util import shebang_matches
+from pygments.formatters import Terminal256Formatter
 
 from coconut.constants import (
     highlight_builtins,
@@ -36,6 +38,9 @@
     template_ext,
     coconut_exceptions,
     main_prompt,
+    style_env_var,
+    default_style,
+    fake_styles,
 )
 
 # -----------------------------------------------------------------------------------------------------------------------
@@ -113,3 +118,14 @@ def __init__(self, stripnl=False, stripall=False, ensurenl=True, tabsize=tabidea
 
     def analyse_text(text):
         return shebang_matches(text, shebang_regex)
+
+
+def highlight_coconut_for_terminal(code):
+    """Highlight Coconut code for the terminal."""
+    style = os.getenv(style_env_var, default_style)
+    if style not in fake_styles:
+        try:
+            return highlight(code, CoconutLexer(), Terminal256Formatter(style=style))
+        except Exception:
+            pass
+    return code

coconut/root.py

@@ -26,7 +26,7 @@
 VERSION = "3.0.4"
 VERSION_NAME = None
 # False for release, int >= 1 for develop
-DEVELOP = 5
+DEVELOP = 6
 ALPHA = False  # for pre releases rather than post releases
 
 assert DEVELOP is False or DEVELOP >= 1, "DEVELOP must be False or an int >= 1"

coconut/terminal.py

@@ -207,15 +207,21 @@ def __init__(self, other=None):
         self.patch_logging()
 
     @classmethod
-    def enable_colors(cls):
+    def enable_colors(cls, file=None):
         """Attempt to enable CLI colors."""
+        if (
+            use_color is False
+            or use_color is None and file is not None and not isatty(file)
+        ):
+            return False
         if not cls.colors_enabled:
             # necessary to resolve https://bugs.python.org/issue40134
             try:
                 os.system("")
             except BaseException:
                 logger.log_exc()
             cls.colors_enabled = True
+        return True
 
     def copy_from(self, other):
         """Copy other onto self."""
@@ -265,11 +271,8 @@ def display(
         else:
             raise CoconutInternalException("invalid logging level", level)
 
-        if use_color is False or (use_color is None and not isatty(file)):
-            color = None
-
         if color:
-            self.enable_colors()
+            color = self.enable_colors(file) and color
 
         raw_message = " ".join(str(msg) for msg in messages)
         # if there's nothing to display but there is a sig, display the sig

coconut/tests/src/extras.coco

@@ -365,6 +365,22 @@ import abc
     except CoconutStyleError as err:
         assert str(err) == """found unused import 'abc' (add '# NOQA' to suppress) (remove --strict to downgrade to a warning) (line 1)
   import abc"""
+    assert_raises(-> parse("""class A(object):
+     1
+     2
+     3
+     4
+     5
+     6
+     7
+     8
+     9
+     10
+     11
+     12
+     13
+     14
+     15"""), CoconutStyleError, err_has="\n ...\n")
 
     setup(line_numbers=False, strict=True, target="sys")
     assert_raises(-> parse("await f x"), CoconutParseError, err_has='invalid use of the keyword "await"')

coconut/util.py

@@ -325,6 +325,19 @@ def replace_all(inputstr, all_to_replace, replace_to):
     return inputstr
 
 
+def highlight(code):
+    """Attempt to highlight Coconut code for the terminal."""
+    from coconut.terminal import logger  # hide to remove circular deps
+    if logger.enable_colors(sys.stdout) and logger.enable_colors(sys.stderr):
+        try:
+            from coconut.highlighter import highlight_coconut_for_terminal
+        except ImportError:
+            pass
+        else:
+            return highlight_coconut_for_terminal(code)
+    return code
+
+
 # -----------------------------------------------------------------------------------------------------------------------
 # VERSIONING:
 # -----------------------------------------------------------------------------------------------------------------------