AST transforms for .length() method call. Fixes natural#17.

Troy Melhase · Troy Melhase · commit 6548316b203e · 2012-05-03T09:38:50.000-04:00
diff --git a/java2python/config/default.py b/java2python/config/default.py
@@ -159,6 +159,9 @@
     (Type('TYPE') > Type('LONG'), transform.typeSub),
     (Type('TYPE') > Type('DOUBLE'), transform.typeSub),
 
+    (Type('METHOD_CALL') > Type('DOT') > Type('IDENT', 'length'),
+     transform.lengthToLen),
+
     (Type('TYPE') > Type('QUALIFIED_TYPE_IDENT') > Type('IDENT'),
      transform.typeSub),
 
@@ -193,7 +196,6 @@
     (r'(\s)(\S*?)(\.toString\(\))', r'\1\2.__str__()'),
     (r'(\s)def toString', r'\1def __str__'),
     (r'(\s)(\S*?)(\.toLowerCase\(\))', r'\1\2.lower()'),
-    (r'(\s)(\S*?)(\.length\(\))', r'\1len(\2)'),
     (r'(.*?)IndexOutOfBoundsException\((.*?)\)', r'\1IndexError(\2)'),
     (r'\.__class__\.getName\(\)', '.__class__.__name__'),
     (r'\.getClass\(\)', '.__class__'),
diff --git a/java2python/mod/transform.py b/java2python/mod/transform.py
@@ -14,6 +14,8 @@
 import keyword
 import types
 
+from java2python.lang import tokens
+
 
 def invalidPythonNames():
     """ Creates a list of valid Java identifiers that are invalid in Python. """
@@ -55,6 +57,38 @@ def syntaxSafeFloatLiteral(node, config):
     node.token.text = value
 
 
+def lengthToLen(node, config):
+    """ Transforms expressions like 'value.length()' to 'len(value)'.
+
+    This method changes AST branches like this:
+
+        METHOD_CALL [start=45, stop=49]
+            DOT . [line=4, start=45, stop=47]
+                IDENT foo [line=4, start=45]
+                IDENT length [line=4, start=47]
+            ARGUMENT_LIST [line=4, start=48, stop=49]
+
+    Into branches like this:
+
+        IDENT len(foo) [line=4, start=45]
+
+    Notice that the resulting IDENT node text is invalid.  We can't use a
+    METHOD_CALL token because those are always bound to a class or instance.
+    It would be best to add a new token type, and that option will be explored
+    if we run into this problem again.
+
+    """
+    dot = node.parent
+    method = dot.parent
+
+    ident = dot.firstChildOfType(tokens.IDENT)
+    ident.token.text = 'len({})'.format(ident.text)
+
+    expr = method.parent
+    expr.children.remove(method)
+    expr.addChild(ident)
+
+
 def typeSub(node, config):
     """ Maps specific, well-known Java types to their Python counterparts.
 
diff --git a/test/Length0.java b/test/Length0.java
@@ -0,0 +1,11 @@
+class Length0 {
+    public static int dummy(int v) {
+        return v + 1;
+    }
+
+    public static void main(String[] args) {
+        String foo = "asdf";
+        System.out.println( dummy(foo.length() ) );
+    }
+
+}
