Fiddle with, and test, format_lines

2 files changed, 31 insertions, 12 deletions

diff --git a/coverage/misc.py b/coverage/misc.py
index 9c4843e..28aa3b0 100644
--- a/coverage/misc.py
+++ b/coverage/misc.py
@@ -110,23 +110,28 @@ def format_lines(statements, lines):
     For example, if `statements` is [1,2,3,4,5,10,11,12,13,14] and
     `lines` is [1,2,5,10,11,13,14] then the result will be "1-2, 5-11, 13-14".
 
+    Both `lines` and `statements` can be any iterable. All of the elements of
+    `lines` must be in `statements`, and all of the values must be positive
+    integers.
+
     """
-    pairs = []
-    i = 0
-    j = 0
-    start = None
     statements = sorted(statements)
     lines = sorted(lines)
-    while i < len(statements) and j < len(lines):
-        if statements[i] == lines[j]:
-            if start is None:
-                start = lines[j]
-            end = lines[j]
-            j += 1
+
+    pairs = []
+    start = None
+    lidx = 0
+    for stmt in statements:
+        if lidx >= len(lines):
+            break
+        if stmt == lines[lidx]:
+            lidx += 1
+            if not start:
+                start = stmt
+            end = stmt
         elif start:
             pairs.append((start, end))
             start = None
-        i += 1
     if start:
         pairs.append((start, end))
     ret = ', '.join(map(nice_pair, pairs))
diff --git a/tests/test_misc.py b/tests/test_misc.py
index be6d110..939b1c9 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -5,7 +5,8 @@
 
 import pytest
 
-from coverage.misc import contract, dummy_decorator_with_args, file_be_gone, Hasher, one_of
+from coverage.misc import contract, dummy_decorator_with_args, file_be_gone
+from coverage.misc import format_lines, Hasher, one_of
 
 from tests.coveragetest import CoverageTest
 
@@ -114,3 +115,16 @@ class ContractTest(CoverageTest):
         assert undecorated(17) == (17, None)
         assert undecorated(b=23) == (None, 23)
         assert undecorated(b=42, a=3) == (3, 42)
+
+
+@pytest.mark.parametrize("statements, lines, result", [
+    (set([1,2,3,4,5,10,11,12,13,14]), set([1,2,5,10,11,13,14]), "1-2, 5-11, 13-14"),
+    ([1,2,3,4,5,10,11,12,13,14,98,99], [1,2,5,10,11,13,14,99], "1-2, 5-11, 13-14, 99"),
+    ([1,2,3,4,98,99,100,101,102,103,104], [1,2,99,102,103,104], "1-2, 99, 102-104"),
+    ([17], [17], "17"),
+    ([90,91,92,93,94,95], [90,91,92,93,94,95], "90-95"),
+    ([1, 2, 3, 4, 5], [], ""),
+    ([1, 2, 3, 4, 5], [4], "4"),
+])
+def test_format_lines(statements, lines, result):
+    assert format_lines(statements, lines) == result