newSpecFile should update scan_id if provided

CHANGES.rst

@@ -40,6 +40,7 @@ Fixes
 -----
 
 * Application new_bluesky_environment would crash when requests package not found.
+* Function newSpecFile did not update scan_id in some cases.
 
 Maintenance
 ------------

bluesky/instrument/callbacks/spec_data_file_writer.py

@@ -48,6 +48,32 @@ def spec_comment(comment, doc=None):
     APS_fw.spec_comment(comment, doc, specwriter)
 
 
+def RE_finder():
+    """
+    Find RunEngine object from namespaces of the stack.
+
+    * Search backwards through each frame in the stack.
+        * Find any RunEngine objects.
+            * Prefer one with name 'RE'.
+            * Otherwise, pick the first one.
+    * Otherwise, return 'None'.
+
+    suggestion: Hoist to apstools.utils
+    """
+    import inspect
+    from bluesky import RunEngine
+
+    fallback = None
+    for fr in inspect.stack():  # Walk backwards from this frame.
+        static = fr.frame.f_locals.copy()  # f_locals will change during 'for'.
+        for k, v in static.items():
+            if isinstance(v, RunEngine):  # Got one!
+                if k == "RE":
+                    return v  # Ideal selection.
+                fallback = fallback or None
+    return fallback
+
+
 def newSpecFile(title, scan_id=None, RE=None):
     """
     User choice of the SPEC file name.
@@ -59,6 +85,7 @@ def newSpecFile(title, scan_id=None, RE=None):
     ``RE.md["scan_id"]`` is set to the last scan number in the file.
     """
     kwargs = {}
+    RE = RE or RE_finder()  # Search for a defined RunEngine instance
     if RE is not None:
         kwargs["RE"] = RE
 

bluesky/tests/test_newSpecFile.py

@@ -6,10 +6,13 @@
 
 import pytest
 from apstools.utils import cleanupText
-from instrument.callbacks.spec_data_file_writer import newSpecFile, specwriter
-from spec2nexus.spec import SpecDataFile, is_spec_file
+from spec2nexus.spec import SpecDataFile
+from spec2nexus.spec import is_spec_file
 
 from bluesky.run_engine import RunEngine
+from instrument.callbacks.spec_data_file_writer import RE_finder
+from instrument.callbacks.spec_data_file_writer import newSpecFile
+from instrument.callbacks.spec_data_file_writer import specwriter
 
 INITIAL_SCAN_ID = 1234
 RE = RunEngine(dict(scan_id=INITIAL_SCAN_ID))
@@ -61,6 +64,37 @@ def test_newSpecFile(title, scan_id, tempdir):
         assert isinstance(specwriter.spec_filename, pathlib.Path)
 
 
+@pytest.mark.parametrize("scan_id", [1, 2, 3, INITIAL_SCAN_ID - 1, INITIAL_SCAN_ID + 1])
+def test_issue_271(scan_id, tempdir):
+    """newSpecFile("title", scan_id=1) did not reset scan id."""
+    found_RE = RE_finder()  # Won't find the one in this module's globals()
+    assert found_RE is None
+
+    RE = RunEngine()  # define for this function, so it can be found
+    found_RE = RE_finder()
+    assert found_RE is not None
+    assert found_RE == RE
+
+    assert isinstance(scan_id, int)
+    assert tempdir.exists()
+    os.chdir(tempdir)  # newSpecFile() works in pwd
+
+    RE.md["scan_id"] = INITIAL_SCAN_ID
+    assert RE.md["scan_id"] == INITIAL_SCAN_ID
+
+    newSpecFile("title", scan_id=scan_id, RE=RE)
+    assert RE.md["scan_id"] != INITIAL_SCAN_ID
+    assert RE.md["scan_id"] == scan_id
+
+    # repeat, without passing RE as parameter
+    RE.md["scan_id"] = INITIAL_SCAN_ID
+    assert RE.md["scan_id"] == INITIAL_SCAN_ID
+
+    newSpecFile("title", scan_id=scan_id)
+    assert RE.md["scan_id"] != INITIAL_SCAN_ID
+    assert RE.md["scan_id"] == scan_id
+
+
 def test_newSpecFile_with_existing(tempdir):
     assert tempdir.exists()
     os.chdir(tempdir)  # newSpecFile() works in pwd