adding directive: unmarshling callback (#12)

* WIP: added a check for wellformness of structs in unmarshling

* added directive to include callbacks at end of unmarshling

* added use of callbacks

* fix: comment

* tidy gomod

gen/elem.go

@@ -125,7 +125,7 @@ var primitives = map[string]Primitive{
 	"interface{}":    Intf,
 	"time.Time":      Time,
 	"msgp.Extension": Ext,
-	"error":	  Error,
+	"error":          Error,
 }
 
 // types built into the library
@@ -136,19 +136,37 @@ var builtins = map[string]struct{}{
 	"msgp.Number": struct{}{},
 }
 
+// Callback represents a function that can is expected to be printed into the generated code.
+// for example, at the end of a successful unmarshalling.
+type Callback struct {
+	Fname        string
+	CallbackType CallbackType
+}
+
+type CallbackType uint64
+
+// UnmarshalCallBack represents a type callback that should run over the generated code.
+const UnmarshalCallBack CallbackType = 1
+
+func (c Callback) IsUnmarshallCallback() bool { return c.CallbackType == UnmarshalCallBack }
+func (c Callback) GetName() string            { return c.Fname }
+
 // common data/methods for every Elem
 type common struct {
 	vname, alias string
 	allocbound   string
+	callbacks    []Callback
 }
 
-func (c *common) SetVarname(s string)    { c.vname = s }
-func (c *common) Varname() string        { return c.vname }
-func (c *common) Alias(typ string)       { c.alias = typ }
-func (c *common) SortInterface() string  { return "" }
-func (c *common) SetAllocBound(s string) { c.allocbound = s }
-func (c *common) AllocBound() string     { return c.allocbound }
-func (c *common) hidden()                {}
+func (c *common) SetVarname(s string)      { c.vname = s }
+func (c *common) Varname() string          { return c.vname }
+func (c *common) Alias(typ string)         { c.alias = typ }
+func (c *common) SortInterface() string    { return "" }
+func (c *common) SetAllocBound(s string)   { c.allocbound = s }
+func (c *common) AllocBound() string       { return c.allocbound }
+func (c *common) GetCallbacks() []Callback { return c.callbacks }
+func (c *common) AddCallback(cb Callback)  { c.callbacks = append(c.callbacks, cb) }
+func (c *common) hidden()                  {}
 
 func IsDangling(e Elem) bool {
 	if be, ok := e.(*BaseElem); ok && be.Dangling() {
@@ -221,6 +239,12 @@ type Elem interface {
 	// when decoding this type.  Meaningful for slices and maps.
 	AllocBound() string
 
+	// AddCallback adds to the elem a Callback it should call at the end of marshaling
+	AddCallback(Callback)
+
+	// GetCallbacks fetches all callbacks this Elem stored.
+	GetCallbacks() []Callback
+
 	hidden()
 }
 

gen/unmarshal.go

@@ -78,6 +78,17 @@ func (u *unmarshalGen) Execute(p Elem) ([]string, error) {
 	u.p.printf("\nfunc (%s %s) UnmarshalMsg(bts []byte) (o []byte, err error) {", c, methodRecv)
 	next(u, p)
 	u.p.print("\no = bts")
+
+	// right before the return: attempt to inspect well formed:
+	for _, callback := range p.GetCallbacks() {
+		if !callback.IsUnmarshallCallback() {
+			continue
+		}
+
+		u.p.printf("\nif err = %s.%s(); err != nil {", c, callback.GetName())
+		u.p.printf("\n  return")
+		u.p.printf("\n}")
+	}
 	u.p.nakedReturn()
 
 	u.p.printf("\nfunc (_ %[2]s) CanUnmarshalMsg(%[1]s interface{}) bool {", c, methodRecv)

go.mod

@@ -3,7 +3,6 @@ module github.com/algorand/msgp
 go 1.12
 
 require (
-	github.com/philhofer/fwd v1.0.0
 	github.com/ttacon/chalk v0.0.0-20160626202418-22c06c80ed31
-	golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d
+	golang.org/x/tools v0.0.0-20200423205358-59e73619c742
 )

go.sum

@@ -1,12 +1,22 @@
-github.com/philhofer/fwd v1.0.0 h1:UbZqGr5Y38ApvM/V/jEljVxwocdweyH+vmYvRPBnbqQ=
-github.com/philhofer/fwd v1.0.0/go.mod h1:gk3iGcWd9+svBvR0sR+KPcfE+RNWozjowpeBVG3ZVNU=
 github.com/ttacon/chalk v0.0.0-20160626202418-22c06c80ed31 h1:OXcKh35JaYsGMRzpvFkLv/MEyPuL49CThT1pZ8aSml4=
 github.com/ttacon/chalk v0.0.0-20160626202418-22c06c80ed31/go.mod h1:onvgF043R+lC5RZ8IT9rBXDaEDnpnw/Cl+HFiw+v/7Q=
+github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/mod v0.2.0 h1:KU7oHjnv3XNWfa5COkzUifxZmxp1TyI7ImMXqFxLwvQ=
+golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d h1:/iIZNFGxc/a7C3yWjGcnboV+Tkc7mxr+p6fDztwoxuM=
-golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20200423205358-59e73619c742 h1:9OGWpORUXvk8AsaBJlpzzDx7Srv/rSK6rvjcsJq4rJo=
+golang.org/x/tools v0.0.0-20200423205358-59e73619c742/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

parse/directives.go

@@ -1,6 +1,7 @@
 package parse
 
 import (
+	"errors"
 	"fmt"
 	"go/ast"
 	"strings"
@@ -26,6 +27,38 @@ var directives = map[string]directive{
 	"tuple":      astuple,
 	"sort":       sortintf,
 	"allocbound": allocbound,
+	// _postunmarshalcheck is used to add callbacks to the end of unmarshling that are tied to a specific Element.
+	_postunmarshalcheck: postunmarshalcheck,
+}
+
+const _postunmarshalcheck = "postunmarshalcheck"
+
+var errNotEnoughArguments = errors.New("postunmarshalcheck did not receive enough arguments. expected at least 3")
+
+//msgp:postunmarshalcheck {Type} {funcName} {funcName} ...
+// the functions should have no params, and output zero.
+func postunmarshalcheck(text []string, f *FileSet) error {
+	if len(text) < 3 {
+		return errNotEnoughArguments
+	}
+	// not error but doesn't do anything
+	if text[0] != _postunmarshalcheck {
+		return nil
+	}
+	text = text[1:]
+
+	elemType := text[0]
+	elem, ok := f.Identities[elemType]
+	if !ok {
+		return errors.New(fmt.Sprintf("postunmarshalcheck error: type %v does not exist", elemType))
+	}
+	for _, fName := range text[1:] {
+		elem.AddCallback(gen.Callback{
+			Fname:        fName,
+			CallbackType: gen.UnmarshalCallBack,
+		})
+	}
+	return nil
 }
 
 var passDirectives = map[string]passDirective{

parse/directives_test.go

@@ -0,0 +1,53 @@
+package parse
+
+import (
+	"testing"
+
+	"github.com/algorand/msgp/gen"
+)
+
+const (
+	testStructName = "TestStruct"
+	testFuncName   = "callback"
+)
+
+func TestPostunmarshalcheck(t *testing.T) {
+	st := gen.Struct{
+		Fields:  nil,
+		AsTuple: false,
+	}
+
+	fl := FileSet{
+		Identities: map[string]gen.Elem{testStructName: &st},
+		Directives: []string{"postunmarshalcheck"}, // raw preprocessor directives
+	}
+	if err := postunmarshalcheck([]string{"postunmarshalcheck", testStructName, testFuncName}, &fl); err != nil {
+		t.Fatal()
+	}
+	if testFuncName != st.GetCallbacks()[0].GetName() {
+		t.Fatal()
+	}
+	if !st.GetCallbacks()[0].IsUnmarshallCallback() {
+		t.Fatal()
+	}
+}
+
+func TestPostunmarshalcheckFailures(t *testing.T) {
+
+	st := gen.Struct{
+		Fields:  nil,
+		AsTuple: false,
+	}
+
+	fl := FileSet{
+		Identities: map[string]gen.Elem{testStructName: &st},
+		Directives: []string{"postunmarshalcheck"}, // raw preprocessor directives
+	}
+	if err := postunmarshalcheck([]string{"postunmarshalcheck", testFuncName}, &fl); err == nil {
+		t.Fatal()
+	}
+
+	if err := postunmarshalcheck([]string{"postunmarshalcheck", "non-existing-type", testFuncName}, &fl); err == nil {
+		t.Fatal()
+	}
+}

parse/getast.go

@@ -532,7 +532,7 @@ func (fs *FileSet) getFieldsFromEmbeddedStruct(importPrefix string, f ast.Expr)
 			return nil
 		}
 
-		return pkgfs.getFieldsFromEmbeddedStruct(pkgid.Name + ".", f.Sel)
+		return pkgfs.getFieldsFromEmbeddedStruct(pkgid.Name+".", f.Sel)
 	default:
 		// other possibilities are disallowed
 		return nil