accounts/abi: handle named ouputs prefixed with underscores (#15766)

* accounts/abi: handle named ouputs prefixed with underscores

* accounts/abi: handle collinding outputs for struct unpacks

* accounts: handle purely underscore output names

4 files changed, 153 insertions, 4 deletions

diff --git a/accounts/abi/argument.go b/accounts/abi/argument.go
index ad17fbf2b..4540c342f 100644
--- a/accounts/abi/argument.go
+++ b/accounts/abi/argument.go
@@ -96,6 +96,20 @@ func (arguments Arguments) unpackTuple(v interface{}, output []byte) error {
 	if err := requireUnpackKind(value, typ, kind, arguments); err != nil {
 		return err
 	}
+	// If the output interface is a struct, make sure names don't collide
+	if kind == reflect.Struct {
+		exists := make(map[string]bool)
+		for _, arg := range arguments {
+			field := capitalise(arg.Name)
+			if field == "" {
+				return fmt.Errorf("abi: purely underscored output cannot unpack to struct")
+			}
+			if exists[field] {
+				return fmt.Errorf("abi: multiple outputs mapping to the same struct field '%s'", field)
+			}
+			exists[field] = true
+		}
+	}
 	// `i` counts the nonindexed arguments.
 	// `j` counts the number of complex types.
 	// both `i` and `j` are used to to correctly compute `data` offset.
@@ -123,10 +137,10 @@ func (arguments Arguments) unpackTuple(v interface{}, output []byte) error {
 
 		switch kind {
 		case reflect.Struct:
+			name := capitalise(arg.Name)
 			for j := 0; j < typ.NumField(); j++ {
-				field := typ.Field(j)
 				// TODO read tags: `abi:"fieldName"`
-				if field.Name == strings.ToUpper(arg.Name[:1])+arg.Name[1:] {
+				if typ.Field(j).Name == name {
 					if err := set(value.Field(j), reflectValue, arg); err != nil {
 						return err
 					}
@@ -222,3 +236,15 @@ func (arguments Arguments) Pack(args ...interface{}) ([]byte, error) {
 
 	return ret, nil
 }
+
+// capitalise makes the first character of a string upper case, also removing any
+// prefixing underscores from the variable names.
+func capitalise(input string) string {
+	for len(input) > 0 && input[0] == '_' {
+		input = input[1:]
+	}
+	if len(input) == 0 {
+		return ""
+	}
+	return strings.ToUpper(input[:1]) + input[1:]
+}
diff --git a/accounts/abi/bind/bind.go b/accounts/abi/bind/bind.go
index 4dce79b77..8175e3cb9 100644
--- a/accounts/abi/bind/bind.go
+++ b/accounts/abi/bind/bind.go
@@ -304,8 +304,15 @@ var methodNormalizer = map[Lang]func(string) string{
 	LangJava: decapitalise,
 }
 
-// capitalise makes the first character of a string upper case.
+// capitalise makes the first character of a string upper case, also removing any
+// prefixing underscores from the variable names.
 func capitalise(input string) string {
+	for len(input) > 0 && input[0] == '_' {
+		input = input[1:]
+	}
+	if len(input) == 0 {
+		return ""
+	}
 	return strings.ToUpper(input[:1]) + input[1:]
 }
 
@@ -315,15 +322,24 @@ func decapitalise(input string) string {
 }
 
 // structured checks whether a method has enough information to return a proper
-// Go struct ot if flat returns are needed.
+// Go struct or if flat returns are needed.
 func structured(method abi.Method) bool {
 	if len(method.Outputs) < 2 {
 		return false
 	}
+	exists := make(map[string]bool)
 	for _, out := range method.Outputs {
+		// If the name is anonymous, we can't organize into a struct
 		if out.Name == "" {
 			return false
 		}
+		// If the field name is empty when normalized or collides (var, Var, _var, _Var),
+		// we can't organize into a struct
+		field := capitalise(out.Name)
+		if field == "" || exists[field] {
+			return false
+		}
+		exists[field] = true
 	}
 	return true
 }
diff --git a/accounts/abi/bind/bind_test.go b/accounts/abi/bind/bind_test.go
index 43ed53b92..896441d79 100644
--- a/accounts/abi/bind/bind_test.go
+++ b/accounts/abi/bind/bind_test.go
@@ -126,6 +126,7 @@ var bindTests = []struct {
 				{"type":"function","name":"namedOutput","constant":true,"inputs":[],"outputs":[{"name":"str","type":"string"}]},
 				{"type":"function","name":"anonOutput","constant":true,"inputs":[],"outputs":[{"name":"","type":"string"}]},
 				{"type":"function","name":"namedOutputs","constant":true,"inputs":[],"outputs":[{"name":"str1","type":"string"},{"name":"str2","type":"string"}]},
+				{"type":"function","name":"collidingOutputs","constant":true,"inputs":[],"outputs":[{"name":"str","type":"string"},{"name":"Str","type":"string"}]},
 				{"type":"function","name":"anonOutputs","constant":true,"inputs":[],"outputs":[{"name":"","type":"string"},{"name":"","type":"string"}]},
 				{"type":"function","name":"mixedOutputs","constant":true,"inputs":[],"outputs":[{"name":"","type":"string"},{"name":"str","type":"string"}]}
 			]
@@ -140,6 +141,7 @@ var bindTests = []struct {
 			 str1, err        = b.NamedOutput(nil)
 			 str1, err        = b.AnonOutput(nil)
 			 res, _          := b.NamedOutputs(nil)
+			 str1, str2, err  = b.CollidingOutputs(nil)
 			 str1, str2, err  = b.AnonOutputs(nil)
 			 str1, str2, err  = b.MixedOutputs(nil)
 
@@ -447,6 +449,66 @@ var bindTests = []struct {
 			}
 		`,
 	},
+	{
+		`Underscorer`,
+		`
+		contract Underscorer {
+			function UnderscoredOutput() constant returns (int _int, string _string) {
+				return (314, "pi");
+			}
+			function LowerLowerCollision() constant returns (int _res, int res) {
+				return (1, 2);
+			}
+			function LowerUpperCollision() constant returns (int _res, int Res) {
+				return (1, 2);
+		  }
+			function UpperLowerCollision() constant returns (int _Res, int res) {
+				return (1, 2);
+			}
+			function UpperUpperCollision() constant returns (int _Res, int Res) {
+				return (1, 2);
+			}
+			function PurelyUnderscoredOutput() constant returns (int _, int res) {
+				return (1, 2);
+			}
+			function AllPurelyUnderscoredOutput() constant returns (int _, int __) {
+				return (1, 2);
+			}
+		}
+		`, `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`,
+		`[{"constant":true,"inputs":[],"name":"LowerUpperCollision","outputs":[{"name":"_res","type":"int256"},{"name":"Res","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"UnderscoredOutput","outputs":[{"name":"_int","type":"int256"},{"name":"_string","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"PurelyUnderscoredOutput","outputs":[{"name":"_","type":"int256"},{"name":"res","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"UpperLowerCollision","outputs":[{"name":"_Res","type":"int256"},{"name":"res","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"AllPurelyUnderscoredOutput","outputs":[{"name":"_","type":"int256"},{"name":"__","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"UpperUpperCollision","outputs":[{"name":"_Res","type":"int256"},{"name":"Res","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"LowerLowerCollision","outputs":[{"name":"_res","type":"int256"},{"name":"res","type":"int256"}],"payable":false,"stateMutability":"view","type":"function"}]`,
+		`
+			// Generate a new random account and a funded simulator
+			key, _ := crypto.GenerateKey()
+			auth := bind.NewKeyedTransactor(key)
+			sim := backends.NewSimulatedBackend(core.GenesisAlloc{auth.From: {Balance: big.NewInt(10000000000)}})
+
+			// Deploy a underscorer tester contract and execute a structured call on it
+			_, _, underscorer, err := DeployUnderscorer(auth, sim)
+			if err != nil {
+				t.Fatalf("Failed to deploy underscorer contract: %v", err)
+			}
+			sim.Commit()
+
+			// Verify that underscored return values correctly parse into structs
+			if res, err := underscorer.UnderscoredOutput(nil); err != nil {
+				t.Errorf("Failed to call constant function: %v", err)
+			} else if res.Int.Cmp(big.NewInt(314)) != 0 || res.String != "pi" {
+				t.Errorf("Invalid result, want: {314, \"pi\"}, got: %+v", res)
+			}
+			// Verify that underscored and non-underscored name collisions force tuple outputs
+			var a, b *big.Int
+
+			a, b, _ = underscorer.LowerLowerCollision(nil)
+			a, b, _ = underscorer.LowerUpperCollision(nil)
+			a, b, _ = underscorer.UpperLowerCollision(nil)
+			a, b, _ = underscorer.UpperUpperCollision(nil)
+			a, b, _ = underscorer.PurelyUnderscoredOutput(nil)
+			a, b, _ = underscorer.AllPurelyUnderscoredOutput(nil)
+
+			fmt.Println(a, b, err)
+		`,
+	},
 }
 
 // Tests that packages generated by the binder can be successfully compiled and
diff --git a/accounts/abi/unpack_test.go b/accounts/abi/unpack_test.go
index 391095073..4d7fe638c 100644
--- a/accounts/abi/unpack_test.go
+++ b/accounts/abi/unpack_test.go
@@ -259,6 +259,51 @@ var unpackTests = []unpackTest{
 		enc:  "000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003",
 		want: [3]*big.Int{big.NewInt(1), big.NewInt(2), big.NewInt(3)},
 	},
+	// struct outputs
+	{
+		def: `[{"name":"int1","type":"int256"},{"name":"int2","type":"int256"}]`,
+		enc: "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
+		want: struct {
+			Int1 *big.Int
+			Int2 *big.Int
+		}{big.NewInt(1), big.NewInt(2)},
+	},
+	{
+		def: `[{"name":"int","type":"int256"},{"name":"Int","type":"int256"}]`,
+		enc: "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
+		want: struct {
+			Int1 *big.Int
+			Int2 *big.Int
+		}{},
+		err: "abi: multiple outputs mapping to the same struct field 'Int'",
+	},
+	{
+		def: `[{"name":"int","type":"int256"},{"name":"_int","type":"int256"}]`,
+		enc: "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
+		want: struct {
+			Int1 *big.Int
+			Int2 *big.Int
+		}{},
+		err: "abi: multiple outputs mapping to the same struct field 'Int'",
+	},
+	{
+		def: `[{"name":"Int","type":"int256"},{"name":"_int","type":"int256"}]`,
+		enc: "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
+		want: struct {
+			Int1 *big.Int
+			Int2 *big.Int
+		}{},
+		err: "abi: multiple outputs mapping to the same struct field 'Int'",
+	},
+	{
+		def: `[{"name":"Int","type":"int256"},{"name":"_","type":"int256"}]`,
+		enc: "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
+		want: struct {
+			Int1 *big.Int
+			Int2 *big.Int
+		}{},
+		err: "abi: purely underscored output cannot unpack to struct",
+	},
 }
 
 func TestUnpack(t *testing.T) {