Try underlying types for named type custom methods

builder/builder.go

@@ -1,6 +1,8 @@
 package builder
 
 import (
+	"go/types"
+
 	"github.com/dave/jennifer/jen"
 	"github.com/jmattheis/goverter/namer"
 	"github.com/jmattheis/goverter/xtype"
@@ -40,6 +42,7 @@ type MethodContext struct {
 	TargetType   *xtype.Type
 	AutoMap      []string
 	Flags        ConversionFlags
+	HasExtend    func(types.Type, types.Type) bool
 	SeenNamed    map[string]struct{}
 
 	TargetVar *jen.Statement

builder/flags.go

@@ -9,6 +9,7 @@ const (
 	FlagIgnoreUnexported
 	FlagZeroValueOnPtrInconsistency
 	FlagSkipCopySameType
+	FlagTryUnderlyingNamedType
 )
 
 type ConversionFlags map[ConversionFlag]bool

builder/underlying.go

@@ -0,0 +1,70 @@
+package builder
+
+import (
+	"github.com/dave/jennifer/jen"
+	"github.com/jmattheis/goverter/xtype"
+)
+
+// TryUnderlyingNamed handles FlagTryUnderlyingNamedType.
+type TryUnderlyingNamed struct{}
+
+// Matches returns true, if the builder can create handle the given types.
+func (*TryUnderlyingNamed) Matches(ctx *MethodContext, source, target *xtype.Type) bool {
+	if !ctx.Flags.Has(FlagTryUnderlyingNamedType) {
+		return false
+	}
+
+	sourceUnderlying, targetUnderlying := findUnderlyingExtendMapping(ctx, source, target)
+	return sourceUnderlying || targetUnderlying
+}
+
+// Build creates conversion source code for the given source and target type.
+func (*TryUnderlyingNamed) Build(gen Generator, ctx *MethodContext, sourceID *xtype.JenID, source, target *xtype.Type) ([]jen.Code, *xtype.JenID, *Error) {
+	sourceUnderlying, targetUnderlying := findUnderlyingExtendMapping(ctx, source, target)
+
+	innerSource := source
+	innerTarget := target
+
+	if sourceUnderlying {
+		innerSource = xtype.TypeOf(source.NamedType.Underlying())
+		sourceID = xtype.OtherID(innerSource.TypeAsJen().Call(sourceID.Code))
+	}
+
+	if targetUnderlying {
+		innerTarget = xtype.TypeOf(target.NamedType.Underlying())
+	}
+
+	stmt, id, err := gen.Build(ctx, sourceID, innerSource, innerTarget, NoWrap)
+	if err != nil {
+		return nil, nil, err.Lift(&Path{
+			SourceID:   "*",
+			SourceType: innerSource.T.String(),
+			TargetID:   "*",
+			TargetType: innerTarget.T.String(),
+		})
+	}
+
+	if targetUnderlying {
+		id = xtype.OtherID(target.TypeAsJen().Call(id.Code))
+	}
+
+	return stmt, id, err
+}
+
+func findUnderlyingExtendMapping(ctx *MethodContext, source, target *xtype.Type) (underlyingSource, underlyingTarget bool) {
+	if source.Named {
+		if ctx.HasExtend(source.NamedType.Underlying(), target.NamedType) {
+			return true, false
+		}
+
+		if target.Named && ctx.HasExtend(source.NamedType.Underlying(), target.NamedType.Underlying()) {
+			return true, true
+		}
+	}
+
+	if target.Named && ctx.HasExtend(source.NamedType, target.NamedType.Underlying()) {
+		return false, true
+	}
+
+	return false, false
+}

comments/parse_docs.go

@@ -232,6 +232,9 @@ func parseConverterComment(comment string, config ConverterConfig) (ConverterCon
 			case "useZeroValueOnPointerInconsistency":
 				config.Flags.Set(builder.FlagZeroValueOnPtrInconsistency)
 				continue
+			case "tryUnderlyingNamedType":
+				config.Flags.Set(builder.FlagTryUnderlyingNamedType)
+				continue
 			}
 			return config, fmt.Errorf("unknown %s comment: %s", prefix, line)
 		}
@@ -330,6 +333,9 @@ func parseMethodComment(comment string) (Method, error) {
 				}
 				m.Flags.Set(builder.FlagWrapErrors)
 				continue
+			case "tryUnderlyingNamedType":
+				m.Flags.Set(builder.FlagTryUnderlyingNamedType)
+				continue
 			}
 			return m, fmt.Errorf("unknown %s comment: %s", prefix, line)
 		}

docs/conversion/misc.md

@@ -202,3 +202,69 @@ func (c *ConverterImpl) Convert(source example.Input) example.Output {
 ```
 
 <!-- tabs:end -->
+
+## Try underlying named types
+
+For each type conversion, goverter will check if there is an existing method
+that can be used. For named types only the type itself will be checked and not
+the underlying type. For this type:
+
+```go
+type InputID  int
+```
+
+`InputID` would be the named type and `int` the underlying type.
+
+With `goverter:tryUnderlyingNamedType`, goverter will check all
+named/underlying combinations.
+
+- named -> underlying
+- underlying -> named
+- underlying -> underlying
+
+<!-- tabs:start -->
+
+#### **input.go**
+
+```go
+package example
+
+// goverter:converter
+// goverter:extend ConvertUnderlying
+type Converter interface {
+    // goverter:tryUnderlyingNamedType
+    Convert(source Input) Output
+}
+func ConvertUnderlying(s int) string {
+    return ""
+}
+// these would be used too
+// func ConvertUnderlying(s int) OutputID
+// func ConvertUnderlying(s InputID) string
+
+type InputID  int
+type OutputID string
+type Input struct  { ID InputID  }
+type Output struct { ID OutputID }
+```
+
+#### **generated/generated.go**
+
+```go
+package generated
+
+import example "goverter/example"
+
+type ConverterImpl struct{}
+
+func (c *ConverterImpl) Convert(source example.Input) example.Output {
+    var output example.Output
+    output.ID = example.OutputID(example.ConvertUnderlying(int(source.ID)))
+    return output
+}
+```
+
+<!-- tabs:end -->
+
+Without the setting only the custom method with this signature could be used
+for the conversion. `func ConvertUnderlying(s InputID) OutputID`

generator/generate.go

@@ -24,6 +24,7 @@ type Config struct {
 
 // BuildSteps that'll used for generation.
 var BuildSteps = []builder.Builder{
+	&builder.TryUnderlyingNamed{},
 	&builder.SkipCopy{},
 	&builder.BasicTargetPointerRule{},
 	&builder.Pointer{},

generator/generator.go

@@ -168,6 +168,15 @@ func (g *generator) appendToFile() {
 	}
 }
 
+func (g *generator) HasExtend(source, target types.Type) bool {
+	signature := xtype.Signature{Source: source.String(), Target: target.String()}
+	_, ok := g.extend[signature]
+	if !ok {
+		_, ok = g.lookup[signature]
+	}
+	return ok
+}
+
 func (g *generator) findOverlappingExplicitStructMethod(method *methodDefinition) (*methodDefinition, bool) {
 	source := method.Source
 	target := method.Target
@@ -211,6 +220,7 @@ func (g *generator) buildMethod(method *methodDefinition, errWrapper builder.Err
 		Fields:       method.Fields,
 		FieldsTarget: fieldsTarget,
 		SeenNamed:    map[string]struct{}{},
+		HasExtend:    g.HasExtend,
 		Flags:        method.Flags,
 		AutoMap:      method.AutoMap,
 		TargetType:   method.Target,
@@ -450,11 +460,5 @@ func (g *generator) Build(
 		return g.Build(ctx, sourceID, source, target, errWrapper)
 	}
 
-	for _, rule := range BuildSteps {
-		if rule.Matches(ctx, source, target) {
-			return rule.Build(g, ctx, sourceID, source, target)
-		}
-	}
-
-	return nil, nil, builder.NewError(fmt.Sprintf("TypeMismatch: Cannot convert %s to %s", source.T, target.T))
+	return g.buildNoLookup(ctx, sourceID, source, target)
 }

scenario/extend_named_underlying_both.yml

@@ -0,0 +1,34 @@
+input:
+    input.go: |
+        package structs
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        type Converter interface {
+            // goverter:tryUnderlyingNamedType
+            Convert(source Input) Output
+        }
+
+        func ConvertUnderlying(s int) string {
+            return ""
+        }
+
+        type InputID  int
+        type OutputID string
+
+        type Input struct  { ID InputID  }
+        type Output struct { ID OutputID }
+success: |
+    // Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+
+    package generated
+
+    import execution "github.com/jmattheis/goverter/execution"
+
+    type ConverterImpl struct{}
+
+    func (c *ConverterImpl) Convert(source execution.Input) execution.Output {
+    	var structsOutput execution.Output
+    	structsOutput.ID = execution.OutputID(execution.ConvertUnderlying(int(source.ID)))
+    	return structsOutput
+    }

scenario/extend_named_underlying_global.yml

@@ -0,0 +1,34 @@
+input:
+    input.go: |
+        package structs
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        // goverter:tryUnderlyingNamedType
+        type Converter interface {
+            Convert(source Input) Output
+        }
+
+        func ConvertUnderlying(s int) string {
+            return ""
+        }
+
+        type InputID  int
+        type OutputID string
+
+        type Input struct  { ID InputID  }
+        type Output struct { ID OutputID }
+success: |
+    // Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+
+    package generated
+
+    import execution "github.com/jmattheis/goverter/execution"
+
+    type ConverterImpl struct{}
+
+    func (c *ConverterImpl) Convert(source execution.Input) execution.Output {
+    	var structsOutput execution.Output
+    	structsOutput.ID = execution.OutputID(execution.ConvertUnderlying(int(source.ID)))
+    	return structsOutput
+    }

scenario/extend_named_underlying_source.yml

@@ -0,0 +1,34 @@
+input:
+    input.go: |
+        package structs
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        type Converter interface {
+            // goverter:tryUnderlyingNamedType
+            Convert(source Input) Output
+        }
+
+        func ConvertUnderlying(s int) OutputID {
+            return ""
+        }
+
+        type InputID  int
+        type OutputID string
+
+        type Input struct  { ID InputID  }
+        type Output struct { ID OutputID }
+success: |
+    // Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+
+    package generated
+
+    import execution "github.com/jmattheis/goverter/execution"
+
+    type ConverterImpl struct{}
+
+    func (c *ConverterImpl) Convert(source execution.Input) execution.Output {
+    	var structsOutput execution.Output
+    	structsOutput.ID = execution.ConvertUnderlying(int(source.ID))
+    	return structsOutput
+    }

scenario/extend_named_underlying_target.yml

@@ -0,0 +1,34 @@
+input:
+    input.go: |
+        package structs
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        type Converter interface {
+            // goverter:tryUnderlyingNamedType
+            Convert(source Input) Output
+        }
+
+        func ConvertUnderlying(s InputID) string {
+            return ""
+        }
+
+        type InputID  int
+        type OutputID string
+
+        type Input struct  { ID InputID  }
+        type Output struct { ID OutputID }
+success: |
+    // Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
+
+    package generated
+
+    import execution "github.com/jmattheis/goverter/execution"
+
+    type ConverterImpl struct{}
+
+    func (c *ConverterImpl) Convert(source execution.Input) execution.Output {
+    	var structsOutput execution.Output
+    	structsOutput.ID = execution.OutputID(execution.ConvertUnderlying(source.ID))
+    	return structsOutput
+    }