1 files changed, 143 insertions, 0 deletions
diff --git a/lib/spack/external/pyrsistent/_transformations.py b/lib/spack/external/pyrsistent/_transformations.py
new file mode 100644
index 0000000000..612098969b
--- /dev/null
+++ b/lib/spack/external/pyrsistent/_transformations.py
@@ -0,0 +1,143 @@
+import re
+import six
+try:
+    from inspect import Parameter, signature
+except ImportError:
+    signature = None
+    try:
+        from inspect import getfullargspec as getargspec
+    except ImportError:
+        from inspect import getargspec
+
+
+_EMPTY_SENTINEL = object()
+
+
+def inc(x):
+    """ Add one to the current value """
+    return x + 1
+
+
+def dec(x):
+    """ Subtract one from the current value """
+    return x - 1
+
+
+def discard(evolver, key):
+    """ Discard the element and returns a structure without the discarded elements """
+    try:
+        del evolver[key]
+    except KeyError:
+        pass
+
+
+# Matchers
+def rex(expr):
+    """ Regular expression matcher to use together with transform functions """
+    r = re.compile(expr)
+    return lambda key: isinstance(key, six.string_types) and r.match(key)
+
+
+def ny(_):
+    """ Matcher that matches any value """
+    return True
+
+
+# Support functions
+def _chunks(l, n):
+    for i in range(0, len(l), n):
+        yield l[i:i + n]
+
+
+def transform(structure, transformations):
+    r = structure
+    for path, command in _chunks(transformations, 2):
+        r = _do_to_path(r, path, command)
+    return r
+
+
+def _do_to_path(structure, path, command):
+    if not path:
+        return command(structure) if callable(command) else command
+
+    kvs = _get_keys_and_values(structure, path[0])
+    return _update_structure(structure, kvs, path[1:], command)
+
+
+def _items(structure):
+    try:
+        return structure.items()
+    except AttributeError:
+        # Support wider range of structures by adding a transform_items() or similar?
+        return list(enumerate(structure))
+
+
+def _get(structure, key, default):
+    try:
+        if hasattr(structure, '__getitem__'):
+            return structure[key]
+
+        return getattr(structure, key)
+
+    except (IndexError, KeyError):
+        return default
+
+
+def _get_keys_and_values(structure, key_spec):
+    if callable(key_spec):
+        # Support predicates as callable objects in the path
+        arity = _get_arity(key_spec)
+        if arity == 1:
+            # Unary predicates are called with the "key" of the path
+            # - eg a key in a mapping, an index in a sequence.
+            return [(k, v) for k, v in _items(structure) if key_spec(k)]
+        elif arity == 2:
+            # Binary predicates are called with the key and the corresponding
+            # value.
+            return [(k, v) for k, v in _items(structure) if key_spec(k, v)]
+        else:
+            # Other arities are an error.
+            raise ValueError(
+                "callable in transform path must take 1 or 2 arguments"
+            )
+
+    # Non-callables are used as-is as a key.
+    return [(key_spec, _get(structure, key_spec, _EMPTY_SENTINEL))]
+
+
+if signature is None:
+    def _get_arity(f):
+        argspec = getargspec(f)
+        return len(argspec.args) - len(argspec.defaults or ())
+else:
+    def _get_arity(f):
+        return sum(
+            1
+            for p
+            in signature(f).parameters.values()
+            if p.default is Parameter.empty
+            and p.kind in (Parameter.POSITIONAL_ONLY, Parameter.POSITIONAL_OR_KEYWORD)
+        )
+
+
+def _update_structure(structure, kvs, path, command):
+    from pyrsistent._pmap import pmap
+    e = structure.evolver()
+    if not path and command is discard:
+        # Do this in reverse to avoid index problems with vectors. See #92.
+        for k, v in reversed(kvs):
+            discard(e, k)
+    else:
+        for k, v in kvs:
+            is_empty = False
+            if v is _EMPTY_SENTINEL:
+                # Allow expansion of structure but make sure to cover the case
+                # when an empty pmap is added as leaf node. See #154.
+                is_empty = True
+                v = pmap()
+
+            result = _do_to_path(v, path, command)
+            if result is not v or is_empty:
+                e[k] = result
+
+    return e.persistent()