Add showExpr and tests for it using variable expressions

src/runtime/python/marshaller.c

@@ -154,7 +154,7 @@ PgfUnmarshaller unmarshaller = { &unmarshallerVtbl };
 
 // ----------------------------------------------------------------------------
 
-static PgfText *
+PgfText *
 PyUnicode_AsPgfText(PyObject *pystr)
 {
     if (!PyUnicode_Check(pystr)) {
@@ -166,7 +166,7 @@ PyUnicode_AsPgfText(PyObject *pystr)
     }
 
     Py_ssize_t size;
-    const char * enc = PyUnicode_AsUTF8AndSize(pystr, &size);
+    const char *enc = PyUnicode_AsUTF8AndSize(pystr, &size);
     PgfText *ptext = malloc(sizeof(PgfText)+size+1);
     memcpy(ptext->text, enc, size+1);
     ptext->size = size;

src/runtime/python/marshaller.h

@@ -6,6 +6,8 @@
 
 #include <pgf/pgf.h>
 
+PgfText *PyUnicode_AsPgfText(PyObject *pystr);
+
 extern PgfUnmarshaller unmarshaller;
 
 extern PgfMarshaller marshaller;

src/runtime/python/pypgf.c

@@ -2541,7 +2541,7 @@ const char *fpath;
     return py_pgf;
 }
 
-static ExprObject*
+static ExprObject *
 pgf_readExpr(PyObject *self, PyObject *args)
 {
     const char *s;
@@ -2563,6 +2563,36 @@ pgf_readExpr(PyObject *self, PyObject *args)
     return (ExprObject *)expr;
 }
 
+static PyObject *
+pgf_showExpr(PyObject *self, PyObject *args)
+{
+    PyObject *pylist;
+    PyObject *pyexpr;
+    if (!PyArg_ParseTuple(args, "O!O!", &PyList_Type, &pylist, &pgf_ExprType, &pyexpr))
+        return NULL;
+
+    PgfPrintContext *ctxt = NULL;
+    for (Py_ssize_t i = PyList_Size(pylist); i > 0 ; i--) {
+        PyObject *item = PyList_GetItem(pylist, i-1);
+        if (!PyUnicode_Check(item)) {
+            PyErr_SetString(PyExc_TypeError, "invalid variable argument in showExpr");
+            return NULL;
+        }
+        PgfText *input = PyUnicode_AsPgfText(item);
+
+        // TODO a better way to copy into this->name?
+        PgfPrintContext *this = (PgfPrintContext *)PyMem_Malloc(sizeof(PgfPrintContext *) + sizeof(PgfText) + input->size + 1);
+        this->next = ctxt;
+        memcpy(&this->name, input, sizeof(PgfText) + input->size + 1);
+        ctxt = this;
+    }
+
+    PgfText *s = pgf_print_expr((PgfExpr) pyexpr, ctxt, 0, &marshaller);
+    PyObject *str = PyUnicode_FromStringAndSize(s->text, s->size);
+    free(s);
+    return str;
+}
+
 static TypeObject *
 pgf_readType(PyObject *self, PyObject *args)
 {
@@ -2594,6 +2624,8 @@ static PyMethodDef module_methods[] = {
      "Reads an NGF file into memory"},
     {"readExpr", (void*)pgf_readExpr, METH_VARARGS,
      "Parses a string as an abstract tree"},
+    {"showExpr", (void*)pgf_showExpr, METH_VARARGS,
+     "Renders an expression as a string"},
     {"readType", (void*)pgf_readType, METH_VARARGS,
      "Parses a string as an abstract type"},
     {NULL, NULL, 0, NULL}        /* Sentinel */

src/runtime/python/test_suite.py

@@ -222,11 +222,6 @@ def test_readExpr_lstr_str():
 
 # expressions: variables
 
-      # ,TestCase (assertEqual "show expression 4" "x" (showExpr ["x"] (EVar 0)))
-      # ,TestCase (assertEqual "show expression 5" "#1" (showExpr ["x"] (EVar 1)))
-      # ,TestCase (assertEqual "show expression 6" "z" (showExpr ["z","y","x"] (EVar 0)))
-      # ,TestCase (assertEqual "show expression 7" "y" (showExpr ["z","y","x"] (EVar 1)))
-
 # def test_readExpr_evar_equality_1():
 #     assert pgf.readExpr("#0") == pgf.ExprVar()
 #     assert pgf.readExpr("#0") == pgf.ExprVar(0)
@@ -240,6 +235,18 @@ def test_readExpr_evar_str_1():
 def test_readExpr_evar_str_2():
     assert str(pgf.ExprVar(42)) == "#42"
 
+def test_showExpr_evar_1():
+    assert pgf.showExpr(["x"], pgf.ExprVar(0)) == "x"
+
+def test_showExpr_evar_2():
+    assert pgf.showExpr(["x"], pgf.ExprVar(1)) == "#1"
+
+def test_showExpr_evar_3():
+    assert pgf.showExpr(["z", "y", "x"], pgf.ExprVar(0)) == "z"
+
+def test_showExpr_evar_4():
+    assert pgf.showExpr(["z", "y", "x"], pgf.ExprVar(1)) == "y"
+
 # expressions: lambda abstractions
 
       # ,TestCase (assertEqual "show expression 8" "\\w->w" (showExpr ["z","y","x"] (EAbs Explicit "w" (EVar 0))))