Have fillDescriptions generate a template for VPSet in cfi files

FWCore/Integration/test/unit_test_outputs/testProducerWithPsetDesc_cfi.py

@@ -187,10 +187,25 @@
     ouDrinks = cms.untracked.uint32(5)
   ),
   test104 = cms.untracked.VPSet(
-    cms.PSet()
+    cms.PSet(),
+    template = cms.PSetTemplate(
+        Drinks = cms.uint32(5),
+        ndoDrinks = cms.optional.uint32,
+        ndouDrinks = cms.optional.untracked.uint32,
+        oDrinks = cms.uint32(5),
+        ouDrinks = cms.untracked.uint32(5),
+        uDrinks = cms.untracked.uint32(5)
+    )
   ),
   test105 = cms.untracked.VPSet(
-  ),
+    template = cms.PSetTemplate(
+        Drinks = cms.uint32(5),
+        ndoDrinks = cms.optional.uint32,
+        ndouDrinks = cms.optional.untracked.uint32,
+        oDrinks = cms.uint32(5),
+        ouDrinks = cms.untracked.uint32(5),
+        uDrinks = cms.untracked.uint32(5)
+    )  ),
   test1 = cms.double(0.1),
   test2 = cms.double(0.2),
   testA = cms.string('fooA'),
@@ -228,6 +243,35 @@
           xvalue = cms.int32(17)
         )
       )
+    ),
+    template = cms.PSetTemplate(
+        Drinks = cms.uint32(5),
+        anotherVPSet = cms.VPSet(
+            cms.PSet(),
+            cms.PSet(
+                xvalue = cms.int32(100)
+            ),
+            template = cms.PSetTemplate(
+                xvalue = cms.int32(7)
+            )
+        ),
+        ndoDrinks = cms.optional.uint32,
+        ndouDrinks = cms.optional.untracked.uint32,
+        oDrinks = cms.uint32(5),
+        ouDrinks = cms.untracked.uint32(5),
+        testDeeplyNested = cms.PSet(
+            bswitch = cms.bool(False),
+            bvalue1 = cms.double(101),
+            bvalue2 = cms.double(101),
+            iswitch = cms.int32(1),
+            ivalue1 = cms.double(101),
+            ivalue2 = cms.untracked.double(101),
+            sswitch = cms.string('1'),
+            svalue1 = cms.double(101),
+            svalue2 = cms.double(101),
+            testint = cms.int32(1000)
+        ),
+        uDrinks = cms.untracked.uint32(5)
     )
   ),
   subpset = cms.PSet(
@@ -369,6 +413,13 @@
     cms.PSet(
       type = cms.string('edmtestAnotherMakerWithRecursivePlugin'),
       value = cms.int32(11)
+    ), 
+    template = cms.PSetTemplate(
+        pluginRecursive = cms.PSet(
+
+        ),
+        type = cms.string('edmtestAnotherMakerWithRecursivePlugin'),
+        value = cms.int32(5)
     )
   ),
   mightGet = cms.optional.untracked.vstring

FWCore/ParameterSet/interface/ParameterSetDescription.h

@@ -296,6 +296,7 @@ namespace edm {
 
     const_iterator end() const { return entries_.end(); }
 
+    bool empty() const noexcept { return entries_.empty(); }
     // Better performance if space is reserved for the number of
     // top level parameters before any are added.
     void reserve(SetDescriptionEntries::size_type n) { entries_.reserve(n); }

FWCore/ParameterSet/python/Config.py

@@ -1059,9 +1059,9 @@ def dumpPython(self, options=PrintOptions()) -> str:
         specialImportRegistry._reset()
         header = "import FWCore.ParameterSet.Config as cms"
         result = "process = cms.Process(\""+self.__name+"\")\n\n"
-        if self.source_():
+        if not self.source_() is None:
             result += "process.source = "+self.source_().dumpPython(options)
-        if self.looper_():
+        if not self.looper_() is None:
             result += "process.looper = "+self.looper_().dumpPython()
         result+=self._dumpPythonList(self.psets, options)
         result+=self._dumpPythonList(self.vpsets, options)
@@ -1103,10 +1103,10 @@ def splitPython(self, options:PrintOptions = PrintOptions()) -> dict:
 
         result = 'process = cms.Process("' + self.__name + '")\n\n'
 
-        if self.source_():
+        if not self.source_() is None:
             parts['source'] = (None, 'source = ' + self.source_().dumpPython(options))
 
-        if self.looper_():
+        if not self.looper_() is None:
             parts['looper'] = (None, 'looper = ' + self.looper_().dumpPython())
 
         parts.update(self._splitPythonList('psets', self.psets, options))

FWCore/ParameterSet/python/Mixins.py

@@ -268,6 +268,8 @@ def __setParameters(self,parameters):
             self.__addParameter(name, value)
         if v is not None:
             self.__validator=v
+    def hasNoParameters(self) -> bool:
+        return len(self.__parameterNames) == 0
     def __setattr__(self,name:str,value):
         #since labels are not supposed to have underscores at the beginning
         # I will assume that if we have such then we are setting an internal variable
@@ -697,7 +699,9 @@ def dumpPython(self, options:PrintOptions=PrintOptions()) -> str:
         if n>=256:
             #wrap in a tuple since they don't have a size constraint
             result+=" ("
+        wroteAtLeastOne = False
         for i, v in enumerate(self):
+            wroteAtLeastOne = True
             if i == 0:
                 if n>nPerLine: result += '\n'+options.indentation()
             else:
@@ -710,7 +714,7 @@ def dumpPython(self, options:PrintOptions=PrintOptions()) -> str:
             result +=' ) '
         moreArgs = self._additionalInitArguments(options)
         if moreArgs:
-            if i > 0:
+            if wroteAtLeastOne:
                 result += ', \n' + options.indentation()
             result += moreArgs
         if n>nPerLine:

FWCore/ParameterSet/python/Types.py

@@ -197,6 +197,8 @@ def __init__(self, *args, **kargs):
     def __call__(self, value):
         self.__dict__
         return self._pset.clone(**value)
+    def _isEmpty(self) -> bool:
+        return self._pset.hasNoParameters()
     def _isValid(self, value) -> bool:
         return isinstance(value,dict) or isinstance(value, PSet)
     def dumpPython(self, options:PrintOptions=PrintOptions()) -> str:
@@ -1459,7 +1461,7 @@ def template(self):
     def copy(self):
         return copy.copy(self)
     def _additionalInitArguments(self, options):
-        if self._template:
+        if self._template and not self._template._isEmpty():
             #NOTE: PSetTemplate.dumpPython does not include the 'cms.' part
             return 'template = cms.'+self._template.dumpPython(options)
         return None
@@ -2420,6 +2422,10 @@ def testVPSetWithTemplate(self):
             ptest = VPSet(PSet(b=int32(3)), template = PSetTemplate(a=required.int32))
             self.assertEqual(len(ptest), 1)
             self.assertEqual(ptest[0].b.value(), 3)
+            self.assertEqual(ptest.dumpPython(),"cms.VPSet(cms.PSet(\n    b = cms.int32(3)\n), \ntemplate = cms.PSetTemplate(\n    a = cms.required.int32\n))"
+                             )
+            ptest = VPSet(template=PSetTemplate())
+            self.assertEqual(ptest.dumpPython(),"cms.VPSet()")
             #will inject `a=required.int32` into the PSet when starting from a dict()
             ptest = VPSet(dict(), template = PSetTemplate(a=required.int32))
             self.assertEqual(len(ptest), 1)

FWCore/ParameterSet/src/ParameterDescription.cc

@@ -365,14 +365,23 @@ namespace edm {
                                                                    int indentation,
                                                                    CfiOptions& options) const {
     bool nextOneStartsWithAComma = false;
-    for_all(vPset_,
-            std::bind(&writeOneElementToCfi,
-                      std::placeholders::_1,
-                      std::ref(os),
-                      indentation,
-                      options,
-                      std::ref(nextOneStartsWithAComma)));
-    os << "\n";
+    for (auto const& p : vPset_) {
+      writeOneElementToCfi(p, os, indentation, options, nextOneStartsWithAComma);
+    }
+    if (cfi::shouldWriteUntyped(options) or psetDesc_->empty() or psetDesc_->anythingAllowed() or
+        psetDesc_->isUnknown()) {
+      os << "\n";
+    } else {
+      if (not vPset_.empty()) {
+        os << ",";
+      }
+      os << "\n";
+      printSpaces(os, indentation + 2);
+      CfiOptions fullOp = cfi::Typed{};
+      os << "template = cms.PSetTemplate(";
+      psetDesc_->writeCfi(os, false, indentation + 4, fullOp);
+      os << ")\n";
+    }
     printSpaces(os, indentation);
   }
 

FWCore/ParameterSet/test/test_catch_ParameterSetDescription.cc

@@ -1398,6 +1398,36 @@ vp = cms.VPSet(
     p = cms.PSet(),
     vp = cms.VPSet(
     )
+  ),
+  template = cms.PSetTemplate(
+    i = cms.required.int32,
+    vi = cms.required.vint32,
+    ui = cms.required.uint32,
+    vui = cms.required.vuint32,
+    l = cms.required.int64,
+    vl = cms.required.vint64,
+    ul = cms.required.uint64,
+    vul = cms.required.vuint64,
+    b = cms.required.bool,
+    d = cms.required.double,
+    vd = cms.required.vdouble,
+    s = cms.required.string,
+    vs = cms.required.vstring,
+    t = cms.required.InputTag,
+    vt = cms.required.VInputTag,
+    et = cms.required.ESInputTag,
+    vet = cms.required.VESInputTag,
+    f = cms.required.FileInPath,
+    e = cms.required.EventID,
+    ve = cms.required.VEventID,
+    L = cms.required.LuminosityBlockID,
+    vL = cms.required.VLuminosityBlockID,
+    er = cms.required.EventRange,
+    ver = cms.required.VEventRange,
+    Lr = cms.required.LuminosityBlockRange,
+    vLr = cms.required.VLuminosityBlockRange,
+    p = cms.PSet(),
+    vp = cms.required.VPSet
   )
 )
 )-";