Initial version of auto-detection of terminal width.

icecream/icecream.py

@@ -16,6 +16,7 @@
 import ast
 import inspect
 import pprint
+import shutil
 import sys
 from datetime import datetime
 from contextlib import contextmanager
@@ -154,15 +155,38 @@ def format_pair(prefix, arg, value):
     return '\n'.join(lines)
 
 
-def argumentToString(obj):
-    s = DEFAULT_ARG_TO_STRING_FUNCTION(obj)
+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 detect_terminal_width(prefix, default=DEFAULT_LINE_WRAP_WIDTH):
+    """ Returns the number of columns that this terminal can handle. """
+    width = default
+    try:
+        if hasattr(shutil, "get_terminal_size"):
+            width = shutil.get_terminal_size().columns
+        else:  # Python 2.x doesn't support get_terminal_size
+            from backports.shutil_get_terminal_size import get_terminal_size
+            width = get_terminal_size().columns
+    except OSError:  # Not in TTY
+        pass
+    return width - len(prefix)
+
+
+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
     contextDelimiter = DEFAULT_CONTEXT_DELIMITER
 
     def __init__(self, prefix=DEFAULT_PREFIX,
@@ -173,6 +197,8 @@ def __init__(self, prefix=DEFAULT_PREFIX,
         self.includeContext = includeContext
         self.outputFunction = outputFunction
         self.argToStringFunction = argToStringFunction
+        self.passWidthParam = supports_param(self.argToStringFunction)
+        self.lineWrapWidth = detect_terminal_width(self.prefix, DEFAULT_LINE_WRAP_WIDTH)
 
     def __call__(self, *args):
         if self.enabled:
@@ -232,7 +258,8 @@ 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 +352,7 @@ 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

setup.py

@@ -103,6 +103,7 @@ def run_tests(self):
         'pygments>=2.2.0',
         'executing>=0.3.1',
         'asttokens>=2.0.1',
+        'backports.shutil-get-terminal-size==1.0.0',
     ],
     cmdclass={
         'test': RunTests,

tests/test_icecream.py

@@ -9,6 +9,7 @@
 #
 # License: MIT
 #
+import textwrap
 
 import sys
 import unittest
@@ -32,6 +33,10 @@
 c = 3
 
 
+def isPython2():
+    return int(sys.version[0]) == 2
+
+
 def noop(*args, **kwargs):
     return
 
@@ -182,6 +187,7 @@ def parseOutputIntoPairs(out, err, assertNumLines,
 class TestIceCream(unittest.TestCase):
     def setUp(self):
         ic._pairDelimiter = TEST_PAIR_DELIMITER
+        ic.lineWrapWidth = icecream.DEFAULT_LINE_WRAP_WIDTH
 
     def testWithoutArgs(self):
         with disableColoring(), captureStandardStreams() as (out, err):
@@ -464,6 +470,7 @@ 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 +525,33 @@ def testColoring(self):
             ic({1: 'str'})  # Output should be colored with ANSI control codes.
 
         assert hasAnsiEscapeCodes(err.getvalue())
+
+    def testStringWithLineLengthOfTen(self):
+        """ Test a string with a short line wrap width. """
+        ic.lineWrapWidth = 10
+        s = "123456789 1234567890"
+        with disableColoring(), captureStandardStreams() as (out, err):
+            ic(s)
+        actual = err.getvalue().strip()
+        if isPython2():
+            self.assertEqual(actual, "ic| s: '123456789 1234567890'")
+        else:
+            expected = textwrap.dedent("""
+            ic| s: ('123456789 '
+                    '1234567890')
+            """).strip()
+            self.assertEqual(actual, expected)
+
+    def testListWithLineLengthOfTen(self):
+        """ Test a list with a short line wrap width. """
+        ic.lineWrapWidth = 10
+        lst = ["1", "2", "3", "4"]
+        with disableColoring(), captureStandardStreams() as (out, err):
+            ic(lst)
+        actual = err.getvalue().strip()
+        expected = textwrap.dedent("""
+        ic| lst: ['1',
+                  '2',
+                  '3',
+                  '4']""").strip()
+        self.assertEqual(actual, expected)