ENH: relax the (zeroGradient, ddt2) replacement token requirement (#1330)

- when a single (non-regex) source field is specified, it is now
  possible to specify the result name without any '@@' substitution
  tokens

src/functionObjects/field/ddt2/ddt2.C

@@ -50,13 +50,15 @@ namespace functionObjects
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-bool Foam::functionObjects::ddt2::checkFormatName(const word& str)
+bool Foam::functionObjects::ddt2::checkFormatName
+(
+    const std::string& str
+)
 {
-    if (str.find("@@") == string::npos)
+    if (std::string::npos == str.find("@@"))
     {
         WarningInFunction
-            << "Bad result naming "
+            << "Bad result naming (no '@@' token found)."
-            << "(no '@@' token found), deactivating."
             << nl << endl;
 
         return false;
@@ -64,10 +66,8 @@ bool Foam::functionObjects::ddt2::checkFormatName(const word& str)
     else if (str == "@@")
     {
         WarningInFunction
-            << "Bad result naming "
+            << "Bad result naming (only a '@@' token found)."
-            << "(only a '@@' token found), deactivating."
+            << nl << endl;
-            << nl
-            << endl;
 
         return false;
     }
@@ -145,7 +145,12 @@ bool Foam::functionObjects::ddt2::read(const dictionary& dict)
         ( mag_ ? "mag(ddt(@@))" : "magSqr(ddt(@@))" )
     );
 
-    if (checkFormatName(resultName_))
+    // Expect '@@' token for result, unless a single (non-regex) source field
+    if
+    (
+        (selectFields_.size() == 1 && selectFields_.first().isLiteral())
+     || checkFormatName(resultName_)
+    )
     {
         blacklist_.set
         (

src/functionObjects/field/ddt2/ddt2.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2019 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -62,7 +62,8 @@ Usage
 
     A list of fields can contain exact names or regular expressions.
     The token '\@\@' in the result name is replaced by the name of the source
-    field.
+    field. In the special case of a single source field (specified as
+    a non-regex), the '\@\@' token checking is suppressed.
 
     The function object will skip over fields that appear to have
     already been processed (ie, their names are similar to the output names).
@@ -100,7 +101,7 @@ class ddt2
 {
     // Private data
 
-        //- Name of fields to process
+        //- Name of fields to process.
         wordRes selectFields_;
 
         //- Formatting for the result fields.
@@ -120,8 +121,8 @@ class ddt2
 
     // Private Member Functions
 
-        //- Check that the word contains the appropriate substitution token(s).
+        //- Check that string contains the appropriate substitution token(s).
-        static bool checkFormatName(const word& str);
+        static bool checkFormatName(const std::string& str);
 
 
         //- Accept unless field name appears to have already been processed

src/functionObjects/field/zeroGradient/zeroGradient.C

@@ -49,13 +49,15 @@ namespace functionObjects
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-bool Foam::functionObjects::zeroGradient::checkFormatName(const word& str)
+bool Foam::functionObjects::zeroGradient::checkFormatName
+(
+    const std::string& str
+)
 {
-    if (str.find("@@") == string::npos)
+    if (std::string::npos == str.find("@@"))
     {
         WarningInFunction
-            << "Bad result naming "
+            << "Bad result naming (no '@@' token found)."
-            << "(no '@@' token found), deactivating."
             << nl << endl;
 
         return false;
@@ -63,10 +65,8 @@ bool Foam::functionObjects::zeroGradient::checkFormatName(const word& str)
     else if (str == "@@")
     {
         WarningInFunction
-            << "Bad result naming "
+            << "Bad result naming (only a '@@' token found)."
-            << "(only a '@@' token found), deactivating."
+            << nl << endl;
-            << nl
-            << endl;
 
         return false;
     }
@@ -118,7 +118,13 @@ bool Foam::functionObjects::zeroGradient::read(const dictionary& dict)
     Info<< type() << " fields: " << selectFields_ << nl;
 
     resultName_ = dict.lookupOrDefault<word>("result", type() + "(@@)");
-    return checkFormatName(resultName_);
+
+    // Require '@@' token for result, unless a single (non-regex) source field
+    return
+    (
+        (selectFields_.size() == 1 && selectFields_.first().isLiteral())
+     || checkFormatName(resultName_)
+    );
 }
 
 

src/functionObjects/field/zeroGradient/zeroGradient.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016-2018 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2019 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -58,7 +58,8 @@ Usage
 
     A list of fields can contain exact names or regular expressions.
     The token '\@\@' in the result name is replaced by the name of the source
-    field.
+    field. In the special case of a single source field (specified as
+    a non-regex), the '\@\@' token checking is suppressed.
 
     The function object will skip over fields that would not benefit
     - ie, only processor, empty, zeroGradient, symmetry patches.
@@ -95,20 +96,20 @@ class zeroGradient
 {
     // Private data
 
-        //- Name of fields to process
+        //- Name of fields to process.
         wordRes selectFields_;
 
         //- Formatting for the result fields.
         word resultName_;
 
-        //- Hashed names of result fields, and their type
+        //- Hashed names of result fields, and their type.
         HashTable<word> results_;
 
 
     // Private Member Functions
 
-        //- Check that the word contains the appropriate substitution token(s).
+        //- Check that string contains the appropriate substitution token(s).
-        static bool checkFormatName(const word& str);
+        static bool checkFormatName(const std::string& str);
 
 
         //- Accept unless field only has constraint patches