Bug 1224452 - Add an expand_variables helper function to do simple make-like variable expansion. r=gps

python/mozbuild/mozbuild/test/test_util.py

@@ -20,11 +20,13 @@ from mozunit import (
 )
 
 from mozbuild.util import (
+    expand_variables,
     FileAvoidWrite,
     group_unified_files,
     hash_file,
     memoize,
     memoized_property,
+    pair,
     resolve_target_to_make,
     MozbuildDeletionError,
     HierarchicalStringList,
@@ -720,5 +722,43 @@ class TestGroupUnifiedFiles(unittest.TestCase):
         self.assertEqual(mapping[1][1], sorted_files[5:10])
         self.assertEqual(mapping[2][1], sorted_files[10:])
 
+
+class TestMisc(unittest.TestCase):
+    def test_pair(self):
+        self.assertEqual(
+            list(pair([1, 2, 3, 4, 5, 6])),
+            [(1, 2), (3, 4), (5, 6)]
+        )
+
+        self.assertEqual(
+            list(pair([1, 2, 3, 4, 5, 6, 7])),
+            [(1, 2), (3, 4), (5, 6), (7, None)]
+        )
+
+    def test_expand_variables(self):
+        self.assertEqual(
+            expand_variables('$(var)', {'var': 'value'}),
+            'value'
+        )
+
+        self.assertEqual(
+            expand_variables('$(a) and $(b)', {'a': '1', 'b': '2'}),
+            '1 and 2'
+        )
+
+        self.assertEqual(
+            expand_variables('$(a) and $(undefined)', {'a': '1', 'b': '2'}),
+            '1 and '
+        )
+
+        self.assertEqual(
+            expand_variables('before $(string) between $(list) after', {
+                'string': 'abc',
+                'list': ['a', 'b', 'c']
+            }),
+            'before abc between a b c after'
+        )
+
+
 if __name__ == '__main__':
     main()

python/mozbuild/mozbuild/util.py

@@ -14,6 +14,7 @@ import functools
 import hashlib
 import itertools
 import os
+import re
 import stat
 import sys
 import time
@@ -934,3 +935,36 @@ def group_unified_files(files, unified_prefix, unified_suffix,
                                               files)):
         just_the_filenames = list(filter_out_dummy(unified_group))
         yield '%s%d.%s' % (unified_prefix, i, unified_suffix), just_the_filenames
+
+
+def pair(iterable):
+    '''Given an iterable, returns an iterable pairing its items.
+
+    For example,
+        list(pair([1,2,3,4,5,6]))
+    returns
+        [(1,2), (3,4), (5,6)]
+    '''
+    i = iter(iterable)
+    return itertools.izip_longest(i, i)
+
+
+VARIABLES_RE = re.compile('\$\((\w+)\)')
+
+
+def expand_variables(s, variables):
+    '''Given a string with $(var) variable references, replace those references
+    with the corresponding entries from the given `variables` dict.
+
+    If a variable value is not a string, it is iterated and its items are
+    joined with a whitespace.'''
+    result = ''
+    for s, name in pair(VARIABLES_RE.split(s)):
+        result += s
+        value = variables.get(name)
+        if not value:
+            continue
+        if not isinstance(value, types.StringTypes):
+            value = ' '.join(value)
+        result += value
+    return result