Much better version of new error messages.

This version is much simpler.

At the point that the exception is raised, we don't have access to
the actual source, just the current expression. but as the
exception percolates up, we can intercept it, add the source and
the re-raise it.

Then at the final point, in the cmdline handler, we can choose to
let the entire traceback print, or just the simpler, direct error
message.

And even with the full traceback, the last bit is nicely formatted
just like the shorter, simpler message.

The error message is colored if clint is installed, but to avoid
yet another dependency, you get monochrome without clint.

I'm sure there is a better way to do the markup, the current method
is kludgy but works.

I wish there was more shared code between HyTypeError and LexException
but they are kind of different in some fundamental ways.

This doesn't work (yet) with runtime errors generated from Python,
like NameError, but I have a method that can catch NameError and turn it
into a more pleasing output.

Finally, there is no obvious way to raise HyTypeError from pure Hy code,
so methods in core/language.hy throw ugly TypeError/ValueError.

hy/cmdline.py

@@ -5,6 +5,7 @@
 # Copyright (c) 2013 Konrad Hinsen <konrad.hinsen@fastmail.net>
 # Copyright (c) 2013 Thom Neale <twneale@gmail.com>
 # Copyright (c) 2013 Will Kahn-Greene <willg@bluesock.org>
+# Copyright (c) 2013 Bob Tolbert <bob@tolbert.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -32,7 +33,7 @@ import sys
 import hy
 
 from hy.lex import LexException, PrematureEndOfInput, tokenize
-from hy.compiler import hy_compile
+from hy.compiler import hy_compile, HyTypeError
 from hy.importer import ast_compile, import_buffer_to_module
 from hy.completer import completion
 
@@ -83,8 +84,11 @@ class HyREPL(code.InteractiveConsole):
             tokens = tokenize(source)
         except PrematureEndOfInput:
             return True
-        except LexException:
+        except LexException as e:
-            self.showsyntaxerror(filename)
+            if e.source is None:
+                e.source = source
+                e.filename = filename
+            print(e)
             return False
 
         try:
@@ -92,6 +96,12 @@ class HyREPL(code.InteractiveConsole):
             if self.spy:
                 print_python_code(_ast)
             code = ast_compile(_ast, filename, symbol)
+        except HyTypeError as e:
+            if e.source is None:
+                e.source = source
+                e.filename = filename
+            print(e)
+            return False
         except Exception:
             self.showtraceback()
             return False
@@ -154,22 +164,34 @@ def ideas_macro():
 require("hy.cmdline", "__console__")
 require("hy.cmdline", "__main__")
 
+SIMPLE_TRACEBACKS = True
+
 
 def run_command(source):
     try:
         import_buffer_to_module("__main__", source)
-    except LexException as exc:
+    except (HyTypeError, LexException) as e:
-        # TODO: This would be better if we had line, col info.
+        if SIMPLE_TRACEBACKS:
-        print(source)
+            print(e)
-        print(repr(exc))
             return 1
+        raise
+    except Exception:
+        raise
     return 0
 
 
 def run_file(filename):
     from hy.importer import import_file_to_module
+    try:
         import_file_to_module("__main__", filename)
-    return 0  # right?
+    except (HyTypeError, LexException) as e:
+        if SIMPLE_TRACEBACKS:
+            print(e)
+            return 1
+        raise
+    except Exception:
+        raise
+    return 0
 
 
 def run_repl(hr=None, spy=False):
@@ -218,6 +240,9 @@ def cmdline_handler(scriptname, argv):
 
     parser.add_argument("-v", action="version", version=VERSION)
 
+    parser.add_argument("--show_tracebacks", action="store_true",
+                        help="show complete tracebacks for Hy exceptions")
+
     # this will contain the script/program name and any arguments for it.
     parser.add_argument('args', nargs=argparse.REMAINDER,
                         help=argparse.SUPPRESS)
@@ -228,6 +253,10 @@ def cmdline_handler(scriptname, argv):
 
     options = parser.parse_args(argv[1:])
 
+    if options.show_tracebacks:
+        global SIMPLE_TRACEBACKS
+        SIMPLE_TRACEBACKS = False
+
     # reset sys.argv like Python
     sys.argv = options.args or [""]
 

hy/compiler.py

@@ -4,6 +4,7 @@
 # Copyright (c) 2013 Julien Danjou <julien@danjou.info>
 # Copyright (c) 2013 Nicolas Dandrimont <nicolas.dandrimont@crans.org>
 # Copyright (c) 2013 James King <james@agentultra.com>
+# Copyright (c) 2013 Bob Tolbert <bob@tolbert.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -93,11 +94,52 @@ class HyTypeError(TypeError):
     def __init__(self, expression, message):
         super(HyTypeError, self).__init__(message)
         self.expression = expression
+        self.message = message
+        self.source = None
+        self.filename = None
 
     def __str__(self):
-        return (super(HyTypeError, self).__str__() + " (line %s, column %d)"
+        from hy.errors import colored
-                % (self.expression.start_line,
+
-                   self.expression.start_column))
+        line = self.expression.start_line
+        start = self.expression.start_column
+        end = self.expression.end_column
+
+        source = []
+        if self.source is not None:
+            source = self.source.split("\n")[line-1:self.expression.end_line]
+
+            if line == self.expression.end_line:
+                length = end - start
+            else:
+                length = len(source[0]) - start
+
+        result = ""
+
+        result += '  File "%s", line %d, column %d\n\n' % (self.filename,
+                                                           line,
+                                                           start)
+
+        if len(source) == 1:
+            result += '  %s\n' % colored.red(source[0])
+            result += '  %s%s\n' % (' '*(start-1),
+                                    colored.green('^' + '-'*(length-1) + '^'))
+        if len(source) > 1:
+            result += '  %s\n' % colored.red(source[0])
+            result += '  %s%s\n' % (' '*(start-1),
+                                    colored.green('^' + '-'*length))
+            if len(source) > 2:  # write the middle lines
+                for line in source[1:-1]:
+                    result += '  %s\n' % colored.red("".join(line))
+                    result += '  %s\n' % colored.green("-"*len(line))
+
+            # write the last line
+            result += '  %s\n' % colored.red("".join(source[-1]))
+            result += '  %s\n' % colored.green('-'*(end-1) + '^')
+
+        result += colored.yellow("HyTypeError: %s\n\n" % self.message)
+
+        return result
 
 
 _compile_table = {}
@@ -341,7 +383,7 @@ def checkargs(exact=None, min=None, max=None, even=None):
             if min is not None and (len(expression) - 1) < min:
                 _raise_wrong_args_number(
                     expression,
-                    "`%%s' needs at least %d arguments, got %%d" % (min))
+                    "`%%s' needs at least %d arguments, got %%d." % (min))
 
             if max is not None and (len(expression) - 1) > max:
                 _raise_wrong_args_number(
@@ -430,6 +472,8 @@ class HyASTCompiler(object):
             # nested; so let's re-raise this exception, let's not wrap it in
             # another HyCompileError!
             raise
+        except HyTypeError as e:
+            raise
         except Exception as e:
             raise HyCompileError(e, sys.exc_info()[2])
 
@@ -1584,6 +1628,9 @@ class HyASTCompiler(object):
                 fn.replace(ofn)
 
                 # Get the object we want to take an attribute from
+                if len(expression) < 2:
+                    raise HyTypeError(expression,
+                                      "attribute access requires object")
                 func = self.compile(expression.pop(1))
 
                 # And get the attribute

hy/errors.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2013 Paul Tagliamonte <paultag@debian.org>
+# Copyright (c) 2013 Bob Tolbert <bob@tolbert.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -25,3 +26,41 @@ class HyError(Exception):
     Exception.
     """
     pass
+
+
+try:
+    from clint.textui import colored
+except:
+    class colored:
+
+        @staticmethod
+        def black(foo):
+            return foo
+
+        @staticmethod
+        def red(foo):
+            return foo
+
+        @staticmethod
+        def green(foo):
+            return foo
+
+        @staticmethod
+        def yellow(foo):
+            return foo
+
+        @staticmethod
+        def blue(foo):
+            return foo
+
+        @staticmethod
+        def magenta(foo):
+            return foo
+
+        @staticmethod
+        def cyan(foo):
+            return foo
+
+        @staticmethod
+        def white(foo):
+            return foo

hy/importer.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2013 Paul Tagliamonte <paultag@debian.org>
+# Copyright (c) 2013 Bob Tolbert <bob@tolbert.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -19,10 +20,9 @@
 # DEALINGS IN THE SOFTWARE.
 
 from py_compile import wr_long, MAGIC
-from hy.compiler import hy_compile
+from hy.compiler import hy_compile, HyTypeError
 from hy.models import HyObject
-from hy.lex import tokenize
+from hy.lex import tokenize, LexException
-
 
 from io import open
 import marshal
@@ -73,17 +73,29 @@ def import_file_to_module(module_name, fpath):
         mod = imp.new_module(module_name)
         mod.__file__ = fpath
         eval(ast_compile(_ast, fpath, "exec"), mod.__dict__)
+    except (HyTypeError, LexException) as e:
+        if e.source is None:
+            fp = open(fpath, 'rt')
+            e.source = fp.read()
+            fp.close()
+            e.filename = fpath
+        raise
     except Exception:
         sys.modules.pop(module_name, None)
         raise
-
     return mod
 
 
 def import_buffer_to_module(module_name, buf):
+    try:
         _ast = import_buffer_to_ast(buf, module_name)
         mod = imp.new_module(module_name)
         eval(ast_compile(_ast, "", "exec"), mod.__dict__)
+    except (HyTypeError, LexException) as e:
+        if e.source is None:
+            e.source = buf
+            e.filename = '<stdin>'
+        raise
     return mod
 
 

hy/lex/__init__.py

@@ -33,6 +33,5 @@ def tokenize(buf):
         return parser.parse(lexer.lex(buf))
     except LexingError as e:
         pos = e.getsourcepos()
-        raise LexException(
+        raise LexException("Could not identify the next token.",
-            "Could not identify the next token at line %s, column %s" % (
+                           pos.lineno, pos.colno)
-                pos.lineno, pos.colno))

hy/lex/exceptions.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2013 Nicolas Dandrimont <nicolas.dandrimont@crans.org>
+# Copyright (c) 2013 Bob Tolbert <bob@tolbert.org>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -23,9 +24,43 @@ from hy.errors import HyError
 
 class LexException(HyError):
     """Error during the Lexing of a Hython expression."""
-    pass
+    def __init__(self, message, lineno, colno):
+        super(LexException, self).__init__(message)
+        self.message = message
+        self.lineno = lineno
+        self.colno = colno
+        self.source = None
+        self.filename = '<stdin>'
+
+    def __str__(self):
+        from hy.errors import colored
+
+        line = self.lineno
+        start = self.colno
+
+        result = ""
+
+        source = self.source.split("\n")
+
+        if line > 0 and start > 0:
+            result += '  File "%s", line %d, column %d\n\n' % (self.filename,
+                                                               line,
+                                                               start)
+
+            if len(self.source) > 0:
+                source_line = source[line-1]
+            else:
+                source_line = ""
+
+            result += '  %s\n' % colored.red(source_line)
+            result += '  %s%s\n' % (' '*(start-1), colored.green('^'))
+
+        result += colored.yellow("LexException: %s\n\n" % self.message)
+
+        return result
 
 
 class PrematureEndOfInput(LexException):
     """We got a premature end of input"""
-    pass
+    def __init__(self, message):
+        super(PrematureEndOfInput, self).__init__(message, -1, -1)

hy/lex/parser.py

@@ -258,12 +258,11 @@ def t_identifier(p):
 def error_handler(token):
     tokentype = token.gettokentype()
     if tokentype == '$end':
-        raise PrematureEndOfInput
+        raise PrematureEndOfInput("Premature end of input")
     else:
         raise LexException(
-            "Ran into a %s where it wasn't expected at line %s, column %s" %
+            "Ran into a %s where it wasn't expected." % tokentype,
-            (tokentype, token.source_pos.lineno, token.source_pos.colno)
+            token.source_pos.lineno, token.source_pos.colno)
-        )
 
 
 parser = pg.build()

tests/compilers/test_ast.py

@@ -22,6 +22,7 @@
 from __future__ import unicode_literals
 
 from hy import HyString
+from hy.models import HyObject
 from hy.compiler import hy_compile, HyCompileError, HyTypeError
 from hy.lex import tokenize
 
@@ -42,10 +43,14 @@ def can_compile(expr):
 
 
 def cant_compile(expr):
-    expr = tokenize(expr)
     try:
-        hy_compile(expr, "__main__")
+        hy_compile(tokenize(expr), "__main__")
         assert False
+    except HyTypeError as e:
+        # Anything that can't be compiled should raise a user friendly
+        # error, otherwise it's a compiler bug.
+        assert isinstance(e.expression, HyObject)
+        assert e.message
     except HyCompileError as e:
         # Anything that can't be compiled should raise a user friendly
         # error, otherwise it's a compiler bug.
@@ -422,8 +427,7 @@ def test_compile_error():
     """Ensure we get compile error in tricky cases"""
     try:
         can_compile("(fn [] (= 1))")
-    except HyCompileError as e:
+    except HyTypeError as e:
-        assert(str(e)
+        assert(e.message == "`=' needs at least 2 arguments, got 1.")
-               == "`=' needs at least 2 arguments, got 1 (line 1, column 8)")
     else:
         assert(False)

tests/test_bin.py

@@ -64,7 +64,7 @@ def test_bin_hy_cmd():
 
     ret = run_cmd("hy -c \"(koan\"")
     assert ret[0] == 1
-    assert "PrematureEndOfInput" in ret[1]
+    assert "Premature end of input" in ret[1]
 
 
 def test_bin_hy_icmd():