ENH: add 'default' as possible Switch state, but not as input/output

- in some circumstances we need to pass a bool value upwards to the
  caller and know if the true/false value was set based on real input
  or is a default value.

  Eg, in the object::read() we might normally have

     enabled_(dict.readIfPresent(key, true));

  but would lose information about why the value is true/false.

  We can change that by using

     enabled_(dict.readIfPresent<Switch>(key, Switch::DEFAULT_ON));

  After which we can use this information is testing.

      if
      (
          child.enabled().nonDefault()
        ? child.enabled()
        : parent.enabled()
      )
      { ... }

   And thus enable output if the parent requested it explicitly or by
   default and it has not been explicitly disabled in the child.

  No difference when testing as a bool and the text representation
  of DEFAULT_ON / DEFAULT_OFF will simply be "true" / "false".

ENH: add construction of Switch from dictionary (similar to Enum)

src/OpenFOAM/primitives/bools/Switch/Switch.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017-2018 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -121,6 +121,54 @@ Foam::Switch Foam::Switch::lookupOrAddToDict
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
+Foam::Switch::Switch
+(
+    const word& key,
+    const dictionary& dict
+)
+{
+    const word str(dict.get<word>(key, keyType::LITERAL));
+
+    (*this) = parse(str, true);
+
+    if (!valid())
+    {
+        FatalIOErrorInFunction(dict)
+            << "Expected 'true/false', 'on/off' ... found " << str << nl
+            << exit(FatalIOError);
+    }
+}
+
+
+Foam::Switch::Switch
+(
+    const word& key,
+    const dictionary& dict,
+    const Switch defaultValue
+)
+:
+    Switch(defaultValue)
+{
+    const entry* eptr = dict.findEntry(key, keyType::LITERAL);
+
+    if (eptr)
+    {
+        const word str(eptr->get<word>());
+
+        (*this) = parse(str, true);
+
+        if (!valid())
+        {
+            // Found entry, but was bad input
+
+            FatalIOErrorInFunction(dict)
+                << "Expected 'true/false', 'on/off' ... found " << str << nl
+                << exit(FatalIOError);
+        }
+    }
+}
+
+
 Foam::Switch::Switch(Istream& is)
 {
     is >> *this;
@@ -131,19 +179,37 @@ Foam::Switch::Switch(Istream& is)
 
 bool Foam::Switch::valid() const noexcept
 {
-    return switch_ <= switchType::NONE;
+    return switch_ != switchType::INVALID;
+}
+
+
+Foam::Switch::switchType Foam::Switch::type() const noexcept
+{
+    return switchType(switch_);
+}
+
+
+bool Foam::Switch::isDefault() const noexcept
+{
+    return (switch_ & 0x10);
+}
+
+
+bool Foam::Switch::nonDefault() const noexcept
+{
+    return !isDefault();
 }
 
 
 const char* Foam::Switch::c_str() const noexcept
 {
-    return names[switch_];
+    return names[(switch_ & 0x0F)];
 }
 
 
 std::string Foam::Switch::str() const
 {
-    return names[switch_];
+    return names[(switch_ & 0x0F)];
 }
 
 

src/OpenFOAM/primitives/bools/Switch/Switch.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017-2018 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -81,7 +81,9 @@ public:
         NO      = 2 /*!< "no" */,    YES  = 3 /*!< "yes" */,
         OFF     = 4 /*!< "off" */,   ON   = 5 /*!< "on" */,
         NONE    = 6 /*!< "none" */,
-        INVALID = 8 /*!< "invalid" */
+        INVALID = 8 /*!< "invalid" */,
+        DEFAULT_OFF = 0x10 /*!< off/false (as default value) */,
+        DEFAULT_ON = 0x11  /*!< on/true (as default value) */
     };
 
 
@@ -92,6 +94,7 @@ private:
         //- The logic and enumerated text representation stored in a byte
         unsigned char switch_;
 
+
     // Static Member Functions
 
         //- Return enum value for input string
@@ -152,6 +155,24 @@ public:
             switch_(parse(str, allowBad))
         {}
 
+        //- Construct from dictionary lookup.
+        //  FatalError if anything is incorrect.
+        Switch
+        (
+            const word& key,        //!< Lookup key. Uses LITERAL (not REGEX)
+            const dictionary& dict  //!< dictionary
+        );
+
+        //- Find the key in the dictionary and return the corresponding
+        //- switch value, or the default value.
+        //  FatalError if anything is incorrect.
+        Switch
+        (
+            const word& key,        //!< Lookup key. Uses LITERAL (not REGEX)
+            const dictionary& dict, //!< dictionary
+            const Switch defaultValue //!< fallback if not found
+        );
+
         //- Construct from Istream
         explicit Switch(Istream& is);
 
@@ -159,7 +180,7 @@ public:
     // Helpers
 
         //- Construct from dictionary, supplying default value so that if the
-        //  value is not found, it is added into the dictionary.
+        //- value is not found, it is added into the dictionary.
         static Switch lookupOrAddToDict
         (
             const word& name,
@@ -170,9 +191,18 @@ public:
 
     // Member Functions
 
-        //- Return true if the Switch has a valid value
+        //- True if the Switch has a valid value
         bool valid() const noexcept;
 
+        //- The underlying enumeration value
+        switchType type() const noexcept;
+
+        //- Underlying enumeration is DEFAULT_ON or DEFAULT_OFF
+        bool isDefault() const noexcept;
+
+        //- Underlying enumeration is not DEFAULT_ON or DEFAULT_OFF
+        bool nonDefault() const noexcept;
+
         //- A string representation of the Switch value
         const char* c_str() const noexcept;