add sourcecode capture to lazy[]

Technologicat · Technologicat · commit de169d5f8ef7 · 2021-05-26T03:43:38.000+03:00
This works together with `Lazy`, which now takes an optional `sourcecode`
argument. It is used as part of the repr; useful for debugging.
diff --git a/unpythonic/lazyutil.py b/unpythonic/lazyutil.py
@@ -34,11 +34,20 @@ def _init_module():  # called by unpythonic.__init__ when otherwise done
 class Lazy:
     """Delayed evaluation, with memoization. (A.k.a. *promise* in Racket.)"""
 
-    def __init__(self, thunk):
-        """`thunk`: 0-argument callable to be stored for delayed evaluation."""
+    def __init__(self, thunk, *, sourcecode=None):
+        """Create a `Lazy` promise.
+
+        `thunk`: 0-argument callable to be stored for delayed evaluation.
+
+        `sourcecode`: str, optional, for use by the `lazy[]` macro.
+
+                      Source code of the thunk, if available. Used in the `repr`,
+                      for debug purposes.
+        """
         if not callable(thunk):
             raise TypeError(f"`thunk` must be a callable, got {type(thunk)} with value {repr(thunk)}")
         self.thunk = thunk
+        self.sourcecode = sourcecode
         self.value = _uninitialized
         self.thunk_returned_normally = _uninitialized
 
@@ -62,6 +71,11 @@ def force(self):
         else:
             raise self.value
 
+    def __repr__(self):
+        if self.sourcecode:
+            return f'<unpythonic.lazyutil.Lazy object at 0x{id(self):x}, sourcecode="{self.sourcecode}">'
+        return f"<unpythonic.lazyutil.Lazy object at 0x{id(self):x}, no debug sourcecode>"
+
 def force1(x):
     """Force a ``Lazy`` promise.
 
diff --git a/unpythonic/syntax/lazify.py b/unpythonic/syntax/lazify.py
@@ -7,10 +7,11 @@
                  Starred, keyword, List, Tuple, Dict, Set, Subscript, Load)
 from functools import partial
 
-from mcpyrate.quotes import macros, q, a, h  # noqa: F401
+from mcpyrate.quotes import macros, q, u, a, h  # noqa: F401
 
 from mcpyrate.astfixers import fix_ctx
 from mcpyrate.quotes import capture_as_macro, is_captured_value
+from mcpyrate.unparser import unparse
 from mcpyrate.walkers import ASTTransformer
 
 from .util import (suggest_decorator_index, sort_lambda_decorators, detect_lambda,
@@ -433,7 +434,7 @@ def doit():
 
 # lazy: syntax transformer, lazify a single expression
 def _lazy(tree):
-    return q[h[Lazy](lambda: a[tree])]
+    return q[h[Lazy](lambda: a[tree], sourcecode=u[unparse(tree)])]
 
 # lazyrec: syntax transformer, recursively lazify elements in container literals
 #
