Initial version of auto-detection of terminal width.

icecream/icecream.py

@@ -16,6 +16,7 @@
 import ast
 import inspect
 import pprint
+import os
 import sys
 from datetime import datetime
 from contextlib import contextmanager
@@ -87,6 +88,7 @@ def colorizedStderrPrint(s):
 DEFAULT_CONTEXT_DELIMITER = '- '
 DEFAULT_OUTPUT_FUNCTION = colorizedStderrPrint
 DEFAULT_ARG_TO_STRING_FUNCTION = pprint.pformat
+COLUMN_OVERFLOW = 4  # Line length appears to overflow by 4 characters.
 
 
 class NoSourceAvailableError(OSError):
@@ -154,15 +156,40 @@ def format_pair(prefix, arg, value):
     return '\n'.join(lines)
 
 
-def argumentToString(obj):
-    s = DEFAULT_ARG_TO_STRING_FUNCTION(obj)
+# def argumentToString(obj, width):
+def argumentToString(obj, width=DEFAULT_LINE_WRAP_WIDTH):
+    s = DEFAULT_ARG_TO_STRING_FUNCTION(obj, width=width)
     s = s.replace('\\n', '\n')  # Preserve string newlines in output.
     return s
 
 
+def columns():
+    """ Returns the number of columns that this terminal can handle. """
+    width = DEFAULT_LINE_WRAP_WIDTH
+    try:
+        # TODO come up with a more elegant solution than subtracting
+        #  a seemingly random number of characters.
+        width = os.get_terminal_size().columns - COLUMN_OVERFLOW
+    except OSError:  # Not in TTY
+        pass
+    except AttributeError:  # Python 2.x
+        width = os.environ.get('COLUMNS', DEFAULT_LINE_WRAP_WIDTH)
+    return width
+
+
+def supports_param(fn, param="width"):
+    """ Returns True if the function supports that parameter. """
+    try:
+        from inspect import signature
+        return param in signature(fn).parameters
+    except ImportError:  # Python 2.x
+        from inspect import getargspec
+        return param in getargspec(fn).args
+
+
 class IceCreamDebugger:
     _pairDelimiter = ', '  # Used by the tests in tests/.
-    lineWrapWidth = DEFAULT_LINE_WRAP_WIDTH
+    lineWrapWidth = columns()
     contextDelimiter = DEFAULT_CONTEXT_DELIMITER
 
     def __init__(self, prefix=DEFAULT_PREFIX,
@@ -173,6 +200,7 @@ def __init__(self, prefix=DEFAULT_PREFIX,
         self.includeContext = includeContext
         self.outputFunction = outputFunction
         self.argToStringFunction = argToStringFunction
+        self.passWidthParam = supports_param(self.argToStringFunction)
 
     def __call__(self, *args):
         if self.enabled:
@@ -232,7 +260,8 @@ def _constructArgumentOutput(self, prefix, context, pairs):
         def argPrefix(arg):
             return '%s: ' % arg
 
-        pairs = [(arg, self.argToStringFunction(val)) for arg, val in pairs]
+        kwargs = {"width": self.lineWrapWidth} if self.passWidthParam else {}
+        pairs = [(arg, self.argToStringFunction(val, **kwargs)) for arg, val in pairs]
         # For cleaner output, if <arg> is a literal, eg 3, "string", b'bytes',
         # etc, only output the value, not the argument and the value, as the
         # argument and the value will be identical or nigh identical. Ex: with
@@ -325,6 +354,7 @@ def configureOutput(self, prefix=_absent, outputFunction=_absent,
 
         if argToStringFunction is not _absent:
             self.argToStringFunction = argToStringFunction
+            self.passWidthParam = supports_param(self.argToStringFunction)
 
         if includeContext is not _absent:
             self.includeContext = includeContext

tests/test_icecream.py

@@ -464,6 +464,7 @@ def testSingleTupleArgument(self):
         self.assertEqual(pair, ('(a, b)', '(1, 2)'))
 
     def testMultilineContainerArgs(self):
+        ic.lineWrapWidth = icecream.DEFAULT_LINE_WRAP_WIDTH
         with disableColoring(), captureStandardStreams() as (out, err):
             ic((a,
                 b))
@@ -518,3 +519,13 @@ def testColoring(self):
             ic({1: 'str'})  # Output should be colored with ANSI control codes.
 
         assert hasAnsiEscapeCodes(err.getvalue())
+
+    @unittest.skipIf(int(sys.version[0]) == 2, "pprint doesn't wrap long strings in Python 2.7")
+    def testLineLengthTen(self):
+        """ Test a specific line wrap width. """
+        ic.lineWrapWidth = 10
+        s = "123456789 1234567890"
+        with disableColoring(), captureStandardStreams() as (out, err):
+            ic(s)
+        pair = parseOutputIntoPairs(out, err, 2)[0]
+        self.assertEqual(pair, [('s', "('123456789 '\n '1234567890')")])