[diffoscope] 03/08: presenters: PartialString: add numl, pformatl, formatl convenience methods

[Ximin Luo]

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infinity0 pushed a commit to branch WIP/humungous-diffs
in repository diffoscope.

commit 9514c8b6f2ec0685f79e64620572469507300db4
Author: Ximin Luo <infinity0 at debian.org>
Date:   Mon Jul 3 20:04:02 2017 +0200

    presenters: PartialString: add numl, pformatl, formatl convenience methods
---
 diffoscope/presenters/utils.py | 38 ++++++++++++++++++++++++++++++++++++--
 tests/test_presenters.py       |  6 ++++++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/diffoscope/presenters/utils.py b/diffoscope/presenters/utils.py
index 69040d6..b50d3ac 100644
--- a/diffoscope/presenters/utils.py
+++ b/diffoscope/presenters/utils.py
@@ -129,7 +129,7 @@ class FormatPlaceholder(object):
 
 
 class PartialString(object):
-    """A format string where the "holes" are indexed by arbitrary python
+    r"""A format string where the "holes" are indexed by arbitrary python
     objects instead of string names or integer indexes. This is useful when you
     need to compose these objects together, but don't want users of the partial
     string to have to deal with artificial "indexes" for the holes.
@@ -176,6 +176,16 @@ class PartialString(object):
     ...
     IndexError: tuple index out of range
 
+    If you don't have specific objects to index the holes with, and don't want
+    to create artifical indexes as in the above examples, here is a slightly
+    simpler way of doing it:
+
+    >>> tmpl = PartialString.numl("{0} {1} {2}", 2, object())
+    >>> tmpl.holes
+    (0, 1, <object ...>)
+    >>> tmpl.pformatl("(first hole)", "(second hole)", "(object hole)")
+    PartialString('(first hole) (second hole) (object hole)',)
+
     CAVEATS:
 
     Filling up holes using other PartialStrings, does not play very nicely with
@@ -245,6 +255,10 @@ class PartialString(object):
         new_fmtstr, new_holes = self._pformat(mapping)
         return self.__class__(new_fmtstr, *new_holes)
 
+    def pformatl(self, *args):
+        """Partially apply a list, implicitly mapped from self.holes."""
+        return self.pformat(dict(zip(self.holes, args)))
+
     def format(self, mapping):
         """Fully apply a mapping, returning a string."""
         new_fmtstr, new_holes = self._pformat(mapping)
@@ -252,6 +266,10 @@ class PartialString(object):
             raise ValueError("not all holes filled: %r" % new_holes)
         return new_fmtstr
 
+    def formatl(self, *args):
+        """Fully apply a list, implicitly mapped from self.holes."""
+        return self.format(dict(zip(self.holes, args)))
+
     @classmethod
     def of(cls, obj):
         """Create a partial string for a single object.
@@ -263,6 +281,19 @@ class PartialString(object):
         return cls("{0}", obj)
 
     @classmethod
+    def numl(cls, fmtstr="", nargs=0, *holes):
+        """Create a partial string with some implicit numeric holes.
+
+        Useful in conjuction with PartialString.pformatl.
+
+        >>> PartialString.numl("{0}{1}{2}{3}", 3, "last object")
+        PartialString('{0}{1}{2}{3}', 0, 1, 2, 'last object')
+        >>> _.pformatl(40, 41, 42, "final")
+        PartialString('404142final',)
+        """
+        return cls(fmtstr, *range(nargs), *holes)
+
+    @classmethod
     def cont(cls):
         r"""Create a new empty partial string with a continuation token.
 
@@ -282,7 +313,10 @@ class PartialString(object):
         27
         """
         def cont(t, fmtstr, *holes):
-            return t.pformat({cont: cls(fmtstr, *(holes + (cont,)))})
+            if isinstance(fmtstr, cls):
+                return t.pformat({cont: fmtstr})
+            else:
+                return t.pformat({cont: cls(fmtstr, *(holes + (cont,)))})
         return cls("{0}", cont), cont
 
 
diff --git a/tests/test_presenters.py b/tests/test_presenters.py
index 8fdaab9..12bea69 100644
--- a/tests/test_presenters.py
+++ b/tests/test_presenters.py
@@ -178,3 +178,9 @@ def test_partial_string_cont():
     assert (t.format({key[0]: "line1", key[1]: "line2", key[2]: "line3"})
             == 'x: line1\ny: line2\nz: line3\n')
     assert t.size(hole_size=5) == 27
+
+def test_partial_string_numl():
+    tmpl = PartialString.numl("{0} {1} {2}", 2, object())
+    assert tmpl.holes[:2] == (0, 1)
+    assert tmpl.pformatl("(1)", "(2)", "(o)") == PartialString('(1) (2) (o)')
+

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