Merge pull request #763 from zackmdavis/hy_io_error

improve traceback legibility by means of distinguishing source of IOErrors

AUTHORS

@@ -59,3 +59,4 @@
 * Ilia Choly <ilia.choly@gmail.com>
 * Shrayas Rajagopal <shrayasr@gmail.com>
 * Shenyang Zhao <dev@zsy.im>
+* Zack M. Davis <code@zackmdavis.net>

hy/cmdline.py

@@ -43,6 +43,8 @@ from hy.importer import (ast_compile, import_buffer_to_module,
 from hy.completer import completion
 from hy.completer import Completer
 
+from hy.errors import HyIOError
+
 from hy.macros import macro, require
 from hy.models.expression import HyExpression
 from hy.models.string import HyString
@@ -324,10 +326,10 @@ def cmdline_handler(scriptname, argv):
             # User did "hy <filename>"
             try:
                 return run_file(options.args[0])
-            except IOError as x:
+            except HyIOError as e:
                 sys.stderr.write("hy: Can't open file '%s': [Errno %d] %s\n" %
-                                 (x.filename, x.errno, x.strerror))
-                sys.exit(x.errno)
+                                 (e.filename, e.errno, e.strerror))
+                sys.exit(e.errno)
 
     # User did NOTHING!
     return run_repl(spy=options.spy)

hy/errors.py

@@ -111,3 +111,11 @@ class HyTypeError(TypeError):
 
 class HyMacroExpansionError(HyTypeError):
     pass
+
+
+class HyIOError(HyError, IOError):
+    """
+    Trivial subclass of IOError and HyError, to distinguish between
+    IOErrors thrown by Hy itself as opposed to Hy programs.
+    """
+    pass

hy/importer.py

@@ -22,6 +22,7 @@
 from hy.compiler import hy_compile, HyTypeError
 from hy.models import HyObject
 from hy.lex import tokenize, LexException
+from hy.errors import HyIOError
 
 from io import open
 import marshal
@@ -49,8 +50,11 @@ def import_buffer_to_hst(buf):
 
 def import_file_to_hst(fpath):
     """Import content from fpath and return an Hy AST."""
-    with open(fpath, 'r', encoding='utf-8') as f:
-        return import_buffer_to_hst(f.read())
+    try:
+        with open(fpath, 'r', encoding='utf-8') as f:
+            return import_buffer_to_hst(f.read())
+    except IOError as e:
+        raise HyIOError(e.errno, e.strerror, e.filename)
 
 
 def import_buffer_to_ast(buf, module_name):