make aperture correction registration optional

The aperture correction registration has been done when the plugin is
instantiated because the column names are derived from the configuration
rather than being static. Sometimes you want to turn this off, e.g., when
you will use aperture corrections derived from somewhere else through the
'proxy' mechanism.

python/lsst/meas/extensions/convolved/convolved.py

@@ -93,6 +93,13 @@ class BaseConvolvedFluxConfig(Config):
     maxSincRadius = Field(dtype=float, default=10.0,
                           doc="Largest aperture for which to use the sinc aperture code for Kron (pixels)")
     kronRadiusForFlux = Field(dtype=float, default=2.5, doc="Number of Kron radii for Kron flux")
+    registerForApCorr = Field(dtype=bool, default=True,
+                              doc="Register measurements for aperture correction?\n"
+                                  "The aperture correction registration is done when the plugin is\n"
+                                  "instantiated because the column names are derived from the configuration\n"
+                                  "rather than being static. Sometimes you want to turn this off, e.g.,\n"
+                                  "when you will use aperture corrections derived from somewhere else\n"
+                                  "through the 'proxy' mechanism.")
 
     def setDefaults(self):
         Config.setDefaults(self)
@@ -261,11 +268,12 @@ def __init__(self, config, name, schema, metadata):
         flagDefs = lsst.meas.base.FlagDefinitionList()
         flagDefs.addFailureFlag("error in running ConvolvedFluxPlugin")
         self.flagHandler = lsst.meas.base.FlagHandler.addFields(schema, name, flagDefs)
-        # Trigger aperture corrections for all flux measurements
-        for apName in self.config.getAllApertureResultNames(name):
-            lsst.meas.base.addApCorrName(apName)
-        for kronName in self.config.getAllKronResultNames(name):
-            lsst.meas.base.addApCorrName(kronName)
+        if self.config.registerForApCorr:
+            # Trigger aperture corrections for all flux measurements
+            for apName in self.config.getAllApertureResultNames(name):
+                lsst.meas.base.addApCorrName(apName)
+            for kronName in self.config.getAllKronResultNames(name):
+                lsst.meas.base.addApCorrName(kronName)
 
         self.centroidExtractor = lsst.meas.base.SafeCentroidExtractor(schema, name)