[PATCH 3/3] utils: add trim_version() function

[Ross Burton <ross.burton@intel.com>]

Add a helper function that returns just the first <num_parts> of <version>,
split by periods.  For example, trim_version("1.2.3", 2) will return "1.2".

This should help reduce the spread of numerous copies of this idea across
classes and recipes.

Signed-off-by: Ross Burton <ross.burton@intel.com>
---
 meta/lib/oe/tests/test_utils.py |   20 ++++++++++++++++++++
 meta/lib/oe/utils.py            |   15 +++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/meta/lib/oe/tests/test_utils.py b/meta/lib/oe/tests/test_utils.py
index 8bb36f2..5d9ac52 100644
--- a/meta/lib/oe/tests/test_utils.py
+++ b/meta/lib/oe/tests/test_utils.py
@@ -29,3 +29,23 @@ class TestPackagesFilterOutSystem(unittest.TestCase):
         d.setVar("PACKAGES", "foo foo-data foo-locale-en-gb")
         pkgs = packages_filter_out_system(d)
         self.assertEqual(pkgs, ["foo-data"])
+
+
+class TestTrimVersion(unittest.TestCase):
+    def test_version_exception(self):
+        with self.assertRaises(TypeError):
+            trim_version(None, 2)
+        with self.assertRaises(TypeError):
+            trim_version((1, 2, 3), 2)
+
+    def test_num_exception(self):
+        with self.assertRaises(ValueError):
+            trim_version("1.2.3", 0)
+        with self.assertRaises(ValueError):
+            trim_version("1.2.3", -1)
+
+    def test_valid(self):
+        self.assertEqual(trim_version("1.2.3", 1), "1")
+        self.assertEqual(trim_version("1.2.3", 2), "1.2")
+        self.assertEqual(trim_version("1.2.3", 3), "1.2.3")
+        self.assertEqual(trim_version("1.2.3", 4), "1.2.3")
diff --git a/meta/lib/oe/utils.py b/meta/lib/oe/utils.py
index 0a2092b..82987e8 100644
--- a/meta/lib/oe/utils.py
+++ b/meta/lib/oe/utils.py
@@ -135,3 +135,18 @@ def packages_filter_out_system(d):
 
 def getstatusoutput(cmd):
     return cmdstatus.getstatusoutput(cmd)
+
+
+def trim_version(version, num_parts=2):
+    """
+    Return just the first <num_parts> of <version>, split by periods.  For
+    example, trim_version("1.2.3", 2) will return "1.2".
+    """
+    if type(version) is not str:
+        raise TypeError("Version should be a string")
+    if num_parts < 1:
+        raise ValueError("Cannot split to parts < 1")
+
+    parts = version.split(".")
+    trimmed = ".".join(parts[:num_parts])
+    return trimmed
-- 
1.7.10.4