Support EmPy version 4

changes.d/6248.fix.md

@@ -0,0 +1 @@
+Upgrade to EmPy 4 to fix an issue with stdout in detaching mode.

conda-environment.yml

@@ -21,7 +21,7 @@ dependencies:
   - tomli >=2 # [py<3.11]
 
 # optional dependencies
-  #- empy >=3.3,<3.4
+  #- empy >=4.1
   #- pandas >=1.0,<2
   #- pympler
   #- matplotlib-base

cylc/flow/parsec/empysupport.py

@@ -52,15 +52,19 @@ def empyprocess(
     os.chdir(dir_)
     ftempl = StringIO('\n'.join(flines))
     xtempl = StringIO()
-    interpreter = em.Interpreter(output=em.UncloseableFile(xtempl))
+    # Requires EmPy >= 4.1
+    interpreter = em.Interpreter(
+        output=em.UncloseableFile(xtempl),
+        dispatcher=False  # raise errors to caller
+    )
 
     # Add `CYLC_` environment variables to the global namespace.
     interpreter.updateGlobals(
         get_cylc_env_vars()
     )
 
     try:
-        interpreter.file(ftempl, '<template>', template_vars)
+        interpreter.file(ftempl, locals=template_vars)
     except Exception as exc:
         lineno = interpreter.contexts[-1].identify()[1]
         raise EmPyError(

setup.cfg

@@ -87,7 +87,7 @@ include = cylc*
 
 [options.extras_require]
 empy =
-    EmPy==3.3.*
+    EmPy>=4.1
 graph =
     pillow
 main_loop-log_data_store =