stringutil: refactor core of pprint so it emits chunks

This commit splits the core of pprint() to a new function that is
a generator of chunks instead of a function returning a single
value. This will make it possible to stream output without waiting for
all data to be formatted first. And it will make it easier to
implement support for indenting.

Differential Revision: https://phab.mercurial-scm.org/D4397

mercurial/utils/stringutil.py

@@ -45,30 +45,36 b' def reescape(pat):'
 
 def pprint(o, bprefix=False):
     """Pretty print an object."""
+    return b''.join(pprintgen(o, bprefix=bprefix))
+
+def pprintgen(o, bprefix=False):
+    """Pretty print an object to a generator of atoms."""
+
     if isinstance(o, bytes):
         if bprefix:
-            return "b'%s'" % escapestr(o)
-        return "'%s'" % escapestr(o)
+            yield "b'%s'" % escapestr(o)
+        else:
+            yield "'%s'" % escapestr(o)
     elif isinstance(o, bytearray):
         # codecs.escape_encode() can't handle bytearray, so escapestr fails
         # without coercion.
-        return "bytearray['%s']" % escapestr(bytes(o))
+        yield "bytearray['%s']" % escapestr(bytes(o))
     elif isinstance(o, list):
-        return '[%s]' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
+        yield '[%s]' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
     elif isinstance(o, dict):
-        return '{%s}' % (b', '.join(
+        yield '{%s}' % (b', '.join(
             '%s: %s' % (pprint(k, bprefix=bprefix),
                         pprint(v, bprefix=bprefix))
             for k, v in sorted(o.items())))
     elif isinstance(o, set):
-        return 'set([%s])' % (b', '.join(
+        yield 'set([%s])' % (b', '.join(
             pprint(k, bprefix=bprefix) for k in sorted(o)))
     elif isinstance(o, tuple):
-        return '(%s)' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
+        yield '(%s)' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
     elif isinstance(o, types.GeneratorType):
-        return 'gen[%s]' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
+        yield 'gen[%s]' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
     else:
-        return pycompat.byterepr(o)
+        yield pycompat.byterepr(o)
 
 def prettyrepr(o):
     """Pretty print a representation of a possibly-nested object"""