WIP: Compatibility with EmPy 4

colcon_core/shell/template/__init__.py

@@ -5,9 +5,18 @@
 import os
 
 from colcon_core.logging import colcon_logger
+
+# The complicated import below is meant to handle 3 things:
+# 1.  Empy 4 - the newest version as of 2024-08-07, which has a different
+#     API from Empy 3.
+# 2.  Empy 3 - the version available since 2003.
+# 3.  The ancient "em" tool, which has no relation to what we are doing here
+#     but sadly shares the "em" package name with empy. We can't use that
+#     package, but we detect if it is installed.
+
 try:
+    # Empy 4 and Empy 3 have the Interpreter object, while "em" does not.
     from em import Interpreter
-    from em import OVERRIDE_OPT
 except ImportError as e:
     try:
         import em  # noqa: F401
@@ -18,6 +27,15 @@
         'not be installed since both packages share the same namespace'
     raise e from None
 
+try:
+    # Only Empy 4 has the Configuration object
+    from em import Configuration
+    em_has_configuration = True
+except ImportError:
+    # We have Empy 3
+    from em import OVERRIDE_OPT
+    em_has_configuration = False
+
 logger = colcon_logger.getChild(__name__)
 
 
@@ -33,13 +51,25 @@
     :raises: Any exception which `em.Interpreter.string` might raise
     """
     output = StringIO()
+    interpreter = None
     try:
-        # disable OVERRIDE_OPT to avoid saving / restoring stdout
-        interpreter = CachingInterpreter(
-            output=output, options={OVERRIDE_OPT: False})
+        if em_has_configuration:
+            config = Configuration(
+                defaultRoot=str(template_path),
+                defaultStdout=output,
+                useProxy=False)
+            interpreter = CachingInterpreter(config=config, dispatcher=False)
+        else:
+            # disable OVERRIDE_OPT to avoid saving / restoring stdout
+            interpreter = CachingInterpreter(
+                output=output, options={OVERRIDE_OPT: False})
         with template_path.open('r') as h:
             content = h.read()
-        interpreter.string(content, str(template_path), locals=data)
+        if em_has_configuration:
+            interpreter.string(content, locals=data)
+        else:
+            interpreter.string(content, str(template_path), locals=data)
+
         output = output.getvalue()
     except Exception as e:  # noqa: F841
         logger.error(
@@ -54,21 +84,27 @@
         with destination_path.open('w') as h:
             h.write(output)
     finally:
-        interpreter.shutdown()
+        if interpreter is not None:
+            interpreter.shutdown()
 
 
-class BypassStdoutInterpreter(Interpreter):
-    """Interpreter for EmPy which keeps `stdout` unchanged."""
+cached_tokens = {}
 
-    def installProxy(self):  # noqa: D102 N802
-        # avoid replacing stdout with ProxyFile
-        pass
+empy_inheritance = None
+if em_has_configuration:
+    empy_inheritance = Interpreter
+else:
+    class BypassStdoutInterpreter(Interpreter):
+        """Interpreter for EmPy which keeps `stdout` unchanged."""
 
+        def installProxy(self):  # noqa: D102 N802
+            # avoid replacing stdout with ProxyFile
+            pass
 
-cached_tokens = {}
+    empy_inheritance = BypassStdoutInterpreter
 
 
-class CachingInterpreter(BypassStdoutInterpreter):
+class CachingInterpreter(empy_inheritance):
     """Interpreter for EmPy which which caches parsed tokens."""
 
     def parse(self, scanner, locals=None):  # noqa: A002 D102
@@ -90,4 +126,10 @@
         self.invoke('atParse', scanner=scanner, locals=locals)
         for token in tokens:
             self.invoke('atToken', token=token)
-            token.run(self, locals)
+            if em_has_configuration:
+                self.run(token, locals)
+                scanner.accumulate()
+            else:
+                token.run(self, locals)
+        if em_has_configuration:
+            return True

setup.cfg

@@ -29,7 +29,7 @@ python_requires = >=3.6
 install_requires =
   coloredlogs; sys_platform == 'win32'
   distlib
-  EmPy<4
+  EmPy
   importlib-metadata; python_version < "3.8"
   packaging
   # the pytest dependency and its extensions are provided for convenience