ENH: distinguish between compressible/incompressible coded source

- previously had codeAddSup used for both incompressible and
  compressible source terms. However, it was not actually possible to
  use it for compressible sources since any references to the 'rho'
  parameter would cause a compilation error for the incompressible case.

  Added 'codeAddSupRho' to distinguish the compressible case.
  User must supply one or both of them on input.

etc/codeTemplates/dynamicCode/codedFvOptionTemplate.C

@@ -147,7 +147,7 @@ ${typeName}FvOption${SourceType}::addSup
         Info<< "${typeName}FvOption${SourceType}::addSup()\n";
     }
 
-//{{{ begin code
+//{{{ begin code - warn/fatal if not implemented?
     ${codeAddSup}
 //}}} end code
 }
@@ -163,11 +163,11 @@ ${typeName}FvOption${SourceType}::addSup
 {
     if (${verbose:-false})
     {
-        Info<< "${typeName}FvOption${SourceType}::addSup()\n";
+        Info<< "${typeName}FvOption${SourceType}::addSup(rho)\n";
     }
 
-//{{{ begin code
-    ${codeAddSup}
+//{{{ begin code - warn/fatal if not implemented?
+    ${codeAddSupRho}
 //}}} end code
 }
 

etc/codeTemplates/dynamicCode/codedFvOptionTemplate.H

@@ -35,7 +35,14 @@ Description
 
     codeAddSup
     (
-        fvMatrix<Type}>& eqn,
+        fvMatrix<Type>& eqn,
+        const label fieldi
+    )
+
+    codeAddSupRho
+    (
+        const volScalarField& rho,
+        fvMatrix<Type>& eqn,
         const label fieldi
     )
 

src/OpenFOAM/db/dynamicLibrary/dynamicCode/dynamicCodeContext.C

@@ -100,6 +100,12 @@ bool Foam::dynamicCodeContext::valid() const noexcept
 }
 
 
+const Foam::entry* Foam::dynamicCodeContext::findEntry(const word& key) const
+{
+    return this->dict().findEntry(key, keyType::LITERAL);
+}
+
+
 bool Foam::dynamicCodeContext::readEntry
 (
     const word& key,

src/OpenFOAM/db/dynamicLibrary/dynamicCode/dynamicCodeContext.H

@@ -176,6 +176,9 @@ public:
 
     // Reading
 
+        //- Locate literal dictionary entry, nullptr if not found
+        const entry* findEntry(const word& key) const;
+
         //- Read string entry from context dictionary
         //- append content to SHA1 hashing and add line number etc.
         //

src/fvOptions/sources/general/codedSource/CodedFvSource.C

@@ -79,9 +79,30 @@ void Foam::fv::CodedSource<Type>::prepare
 
     //dynCode.removeFilterVariable("code");
     dynCode.setFilterVariable("codeCorrect", codeCorrect_);
-    dynCode.setFilterVariable("codeAddSup", codeAddSup_);
     dynCode.setFilterVariable("codeConstrain", codeConstrain_);
 
+    // Missing codeAddSup or codeAddSupRho handled on input,
+    // but also check for empty() and inject "NotImplemented" to avoid
+    // cases where the user has specified or used the wrong one
+    // (ie, compresssible vs incompressible)
+
+    if (codeAddSup_.empty())
+    {
+        dynCode.setFilterVariable("codeAddSup", "NotImplemented");
+    }
+    else
+    {
+        dynCode.setFilterVariable("codeAddSup", codeAddSup_);
+    }
+    if (codeAddSupRho_.empty())
+    {
+        dynCode.setFilterVariable("codeAddSupRho", "NotImplemented");
+    }
+    else
+    {
+        dynCode.setFilterVariable("codeAddSupRho", codeAddSupRho_);
+    }
+
     // Compile filtered C template
     dynCode.addCompileFile(codeTemplateC);
 
@@ -154,7 +175,18 @@ bool Foam::fv::CodedSource<Type>::read(const dictionary& dict)
     auto& ctx = codedBase::codeContext();
 
     ctx.readEntry("codeCorrect", codeCorrect_);
-    ctx.readEntry("codeAddSup", codeAddSup_);
+
+    // Need one or both codeAddSup/codeAddSupRho.
+    // - do precheck and let the usual mechanism fail
+
+    const bool mandatory =
+    (
+        !ctx.findEntry("codeAddSup")
+     && !ctx.findEntry("codeAddSupRho")
+    );
+
+    ctx.readEntry("codeAddSup", codeAddSup_, mandatory);
+    ctx.readEntry("codeAddSupRho", codeAddSupRho_, mandatory);
 
     // ctx.readEntry("codeConstrain", codeConstrain_);
     ctx.readEntry  // Compatibility
@@ -233,7 +265,7 @@ void Foam::fv::CodedSource<Type>::addSup
 {
     DebugInfo
         << "fv::CodedSource<" << pTraits<Type>::typeName
-        << ">::addSup for source " << name_ << endl;
+        << ">::addSup(rho) for source " << name_ << endl;
 
     updateLibrary(name_);
     redirectOption().addSup(rho, eqn, fieldi);

src/fvOptions/sources/general/codedSource/CodedFvSource.H

@@ -43,13 +43,20 @@ Description
 
     codeAddSup
     (
-        fvMatrix<Type}>& eqn,
+        fvMatrix<Type>& eqn,
+        const label fieldi
+    )
+
+    codeAddSupRho
+    (
+        const volScalarField& rho,
+        fvMatrix<Type>& eqn,
         const label fieldi
     )
 
     codeConstrain
     (
-        fvMatrix<Type}>& eqn,
+        fvMatrix<Type>& eqn,
         const label fieldi
     )
     \endverbatim
@@ -141,6 +148,7 @@ protected:
 
         string codeCorrect_;
         string codeAddSup_;
+        string codeAddSupRho_;
         string codeConstrain_;
 
         //- Underlying code