Bug 1257516 - Add a file-like class that sends writes to a callback. r=ted

python/mozbuild/mozbuild/configure/util.py

@@ -96,3 +96,36 @@ class ConfigureOutputHandler(logging.Handler):
             raise
         except:
             self.handleError(record)
+
+
+class LineIO(object):
+    '''File-like class that sends each line of the written data to a callback
+    (without carriage returns).
+    '''
+    def __init__(self, callback):
+        self._callback = callback
+        self._buf = ''
+
+    def write(self, buf):
+        lines = buf.splitlines()
+        if not lines:
+            return
+        if self._buf:
+            lines[0] = self._buf + lines[0]
+            self._buf = ''
+        if not buf.endswith('\n'):
+            self._buf = lines.pop()
+
+        for line in lines:
+            self._callback(line)
+
+    def close(self):
+        if self._buf:
+            self._callback(self._buf)
+            self._buf = ''
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()

python/mozbuild/mozbuild/test/configure/test_util.py

@@ -16,6 +16,7 @@ from mozunit import main
 
 from mozbuild.configure.util import (
     ConfigureOutputHandler,
+    LineIO,
     Version,
 )
 
@@ -176,6 +177,50 @@ class TestConfigureOutputHandler(unittest.TestCase):
             os.remove(path)
 
 
+class TestLineIO(unittest.TestCase):
+    def test_lineio(self):
+        lines = []
+        l = LineIO(lambda l: lines.append(l))
+
+        l.write('a')
+        self.assertEqual(lines, [])
+
+        l.write('b')
+        self.assertEqual(lines, [])
+
+        l.write('\n')
+        self.assertEqual(lines, ['ab'])
+
+        l.write('cdef')
+        self.assertEqual(lines, ['ab'])
+
+        l.write('\n')
+        self.assertEqual(lines, ['ab', 'cdef'])
+
+        l.write('ghi\njklm')
+        self.assertEqual(lines, ['ab', 'cdef', 'ghi'])
+
+        l.write('nop\nqrst\nuv\n')
+        self.assertEqual(lines, ['ab', 'cdef', 'ghi', 'jklmnop', 'qrst', 'uv'])
+
+        l.write('wx\nyz')
+        self.assertEqual(lines, ['ab', 'cdef', 'ghi', 'jklmnop', 'qrst', 'uv',
+                                 'wx'])
+
+        l.close()
+        self.assertEqual(lines, ['ab', 'cdef', 'ghi', 'jklmnop', 'qrst', 'uv',
+                                 'wx', 'yz'])
+
+    def test_lineio_contextmanager(self):
+        lines = []
+        with LineIO(lambda l: lines.append(l)) as l:
+            l.write('a\nb\nc')
+
+            self.assertEqual(lines, ['a', 'b'])
+
+        self.assertEqual(lines, ['a', 'b', 'c'])
+
+
 class TestVersion(unittest.TestCase):
     def test_version_simple(self):
         v = Version('1')