genbindings: track optional parameters in our IL, expand in AST pass

cmd/genbindings/clang2il.go

@@ -154,9 +154,15 @@ nextMethod:
 
 						// Update the name for the existing nth parameter
 						mm.Parameters[paramCounter].ParameterName = parmName
-						paramCounter++
 
-						// TODO If this parameter is optional, expand it into multiple function overloads
+						// If this parameter has any internal AST nodes of its
+						// own, assume it means it's an optional parameter
+						if _, ok := methodObj["inner"]; ok {
+							mm.Parameters[paramCounter].Optional = true
+						}
+
+						// Next
+						paramCounter++
 
 					default:
 						// Something else inside a declaration??

cmd/genbindings/intermediate.go

@@ -10,6 +10,7 @@ type CppParameter struct {
 	Const         bool
 	Pointer       bool
 	ByRef         bool
+	Optional      bool
 }
 
 type CppProperty struct {

cmd/genbindings/main.go

@@ -54,6 +54,9 @@ func main() {
 		os.Exit(0)
 	}
 
+	// AST transforms on our IL
+	astTransformOptional(parsed)
+
 	// Emit 3 code files from the intermediate format
 	outputName := filepath.Join(*outDir, "gen_"+strings.TrimSuffix(filepath.Base(*inputHeader), `.h`))
 

cmd/genbindings/transformoptional.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"fmt"
+)
+
+// astTransformOptional expands all methods with optional parameters into
+// explicit additional versions.
+func astTransformOptional(parsed *CppParsedHeader) {
+	for i, c := range parsed.Classes {
+
+		anyChange := false
+		for j, m := range c.Methods {
+
+			// Search for first optional parameter (they all must be last)
+			optionalStart := -1
+			for k, p := range m.Parameters {
+				if p.Optional {
+					optionalStart = k
+					break
+				}
+			}
+			if optionalStart == -1 {
+				continue // There were no optional parameters
+			}
+
+			anyChange = true
+
+			// Add method copies
+			for x := optionalStart; x < len(m.Parameters); x++ {
+				dupMethod := CppMethod{
+					MethodName: m.MethodName + fmt.Sprintf("%d", x+1),
+					ReturnType: m.ReturnType,
+					Parameters: nil,
+				}
+				dupMethod.Parameters = append(dupMethod.Parameters, m.Parameters[0:x+1]...)
+				c.Methods = append(c.Methods, dupMethod) // TODO can we insert them next, instead of at the end?
+			}
+
+			// Truncate the original method's parameters to only the
+			// mandatory ones
+			m.Parameters = m.Parameters[0:optionalStart]
+			c.Methods[j] = m
+		}
+
+		if anyChange {
+			parsed.Classes[i] = c
+		}
+	}
+}