add map key validation support (#324)

README.md

@@ -1,7 +1,7 @@
 Package validator
 ================
 <img align="right" src="https://raw.githubusercontent.com/go-playground/validator/v9/logo.png">[![Join the chat at https://gitter.im/go-playground/validator](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/go-playground/validator?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-![Project status](https://img.shields.io/badge/version-9.8.0-green.svg)
+![Project status](https://img.shields.io/badge/version-9.9.0-green.svg)
 [![Build Status](https://semaphoreci.com/api/v1/joeybloggs/validator/branches/v9/badge.svg)](https://semaphoreci.com/joeybloggs/validator)
 [![Coverage Status](https://coveralls.io/repos/go-playground/validator/badge.svg?branch=v9&service=github)](https://coveralls.io/github/go-playground/validator?branch=v9)
 [![Go Report Card](https://goreportcard.com/badge/github.com/go-playground/validator)](https://goreportcard.com/report/github.com/go-playground/validator)
@@ -13,7 +13,8 @@ Package validator implements value validations for structs and individual fields
 It has the following **unique** features:
 
 -   Cross Field and Cross Struct validations by using validation tags or custom validators.  
--   Slice, Array and Map diving, which allows any or all levels of a multidimensional field to be validated.  
+-   Slice, Array and Map diving, which allows any or all levels of a multidimensional field to be validated.
+-   Ability to dive into both map keys and values for validation  
 -   Handles type interface by determining it's underlying type prior to validation.
 -   Handles custom field types such as sql driver Valuer see [Valuer](https://golang.org/src/database/sql/driver/types.go?s=1210:1293#L29)
 -   Alias validation tags, which allows for mapping of several validations to a single tag for easier defining of validations on structs
@@ -65,61 +66,69 @@ Please see http://godoc.org/gopkg.in/go-playground/validator.v9 for detailed usa
 
 Benchmarks
 ------
-###### Run on MacBook Pro (15-inch, 2017) Go version go1.9.1 linux/amd64
+###### Run on MacBook Pro (15-inch, 2017) Go version go1.9.2 darwin/amd64
 ```go
 go test -bench=. -benchmem=true
-BenchmarkFieldSuccess-8                                       	20000000	        87.2 ns/op	       0 B/op	       0 allocs/op
-BenchmarkFieldSuccessParallel-8                               	50000000	        26.1 ns/op	       0 B/op	       0 allocs/op
-BenchmarkFieldFailure-8                                       	 5000000	       299 ns/op	     208 B/op	       4 allocs/op
-BenchmarkFieldFailureParallel-8                               	20000000	       100 ns/op	     208 B/op	       4 allocs/op
-BenchmarkFieldDiveSuccess-8                                   	 2000000	       645 ns/op	     201 B/op	      11 allocs/op
-BenchmarkFieldDiveSuccessParallel-8                           	10000000	       198 ns/op	     201 B/op	      11 allocs/op
-BenchmarkFieldDiveFailure-8                                   	 2000000	       876 ns/op	     412 B/op	      16 allocs/op
-BenchmarkFieldDiveFailureParallel-8                           	 5000000	       268 ns/op	     413 B/op	      16 allocs/op
-BenchmarkFieldCustomTypeSuccess-8                             	10000000	       228 ns/op	      32 B/op	       2 allocs/op
-BenchmarkFieldCustomTypeSuccessParallel-8                     	20000000	        70.0 ns/op	      32 B/op	       2 allocs/op
-BenchmarkFieldCustomTypeFailure-8                             	 5000000	       286 ns/op	     208 B/op	       4 allocs/op
-BenchmarkFieldCustomTypeFailureParallel-8                     	20000000	        95.6 ns/op	     208 B/op	       4 allocs/op
-BenchmarkFieldOrTagSuccess-8                                  	 2000000	       857 ns/op	      16 B/op	       1 allocs/op
-BenchmarkFieldOrTagSuccessParallel-8                          	 3000000	       397 ns/op	      16 B/op	       1 allocs/op
-BenchmarkFieldOrTagFailure-8                                  	 3000000	       495 ns/op	     224 B/op	       5 allocs/op
-BenchmarkFieldOrTagFailureParallel-8                          	 5000000	       376 ns/op	     224 B/op	       5 allocs/op
-BenchmarkStructLevelValidationSuccess-8                       	10000000	       226 ns/op	      32 B/op	       2 allocs/op
-BenchmarkStructLevelValidationSuccessParallel-8               	20000000	        68.4 ns/op	      32 B/op	       2 allocs/op
-BenchmarkStructLevelValidationFailure-8                       	 3000000	       497 ns/op	     304 B/op	       8 allocs/op
-BenchmarkStructLevelValidationFailureParallel-8               	10000000	       170 ns/op	     304 B/op	       8 allocs/op
-BenchmarkStructSimpleCustomTypeSuccess-8                      	 3000000	       420 ns/op	      32 B/op	       2 allocs/op
-BenchmarkStructSimpleCustomTypeSuccessParallel-8              	20000000	       124 ns/op	      32 B/op	       2 allocs/op
-BenchmarkStructSimpleCustomTypeFailure-8                      	 2000000	       681 ns/op	     424 B/op	       9 allocs/op
-BenchmarkStructSimpleCustomTypeFailureParallel-8              	10000000	       244 ns/op	     440 B/op	      10 allocs/op
-BenchmarkStructFilteredSuccess-8                              	 2000000	       659 ns/op	     288 B/op	       9 allocs/op
-BenchmarkStructFilteredSuccessParallel-8                      	10000000	       211 ns/op	     288 B/op	       9 allocs/op
-BenchmarkStructFilteredFailure-8                              	 3000000	       482 ns/op	     256 B/op	       7 allocs/op
-BenchmarkStructFilteredFailureParallel-8                      	10000000	       162 ns/op	     256 B/op	       7 allocs/op
-BenchmarkStructPartialSuccess-8                               	 3000000	       564 ns/op	     256 B/op	       6 allocs/op
-BenchmarkStructPartialSuccessParallel-8                       	10000000	       180 ns/op	     256 B/op	       6 allocs/op
-BenchmarkStructPartialFailure-8                               	 2000000	       779 ns/op	     480 B/op	      11 allocs/op
-BenchmarkStructPartialFailureParallel-8                       	 5000000	       268 ns/op	     480 B/op	      11 allocs/op
-BenchmarkStructExceptSuccess-8                                	 2000000	       879 ns/op	     496 B/op	      12 allocs/op
+BenchmarkFieldSuccess-8                                       	20000000	        79.9 ns/op	       0 B/op	       0 allocs/op
+BenchmarkFieldSuccessParallel-8                               	50000000	        25.0 ns/op	       0 B/op	       0 allocs/op
+BenchmarkFieldFailure-8                                       	 5000000	       281 ns/op	     208 B/op	       4 allocs/op
+BenchmarkFieldFailureParallel-8                               	20000000	        97.0 ns/op	     208 B/op	       4 allocs/op
+BenchmarkFieldArrayDiveSuccess-8                              	 3000000	       591 ns/op	     201 B/op	      11 allocs/op
+BenchmarkFieldArrayDiveSuccessParallel-8                      	10000000	       195 ns/op	     201 B/op	      11 allocs/op
+BenchmarkFieldArrayDiveFailure-8                              	 2000000	       878 ns/op	     412 B/op	      16 allocs/op
+BenchmarkFieldArrayDiveFailureParallel-8                      	 5000000	       274 ns/op	     413 B/op	      16 allocs/op
+BenchmarkFieldMapDiveSuccess-8                                	 1000000	      1279 ns/op	     432 B/op	      18 allocs/op
+BenchmarkFieldMapDiveSuccessParallel-8                        	 5000000	       401 ns/op	     432 B/op	      18 allocs/op
+BenchmarkFieldMapDiveFailure-8                                	 1000000	      1060 ns/op	     512 B/op	      16 allocs/op
+BenchmarkFieldMapDiveFailureParallel-8                        	 5000000	       334 ns/op	     512 B/op	      16 allocs/op
+BenchmarkFieldMapDiveWithKeysSuccess-8                        	 1000000	      1462 ns/op	     480 B/op	      21 allocs/op
+BenchmarkFieldMapDiveWithKeysSuccessParallel-8                	 3000000	       463 ns/op	     480 B/op	      21 allocs/op
+BenchmarkFieldMapDiveWithKeysFailure-8                        	 1000000	      1414 ns/op	     721 B/op	      21 allocs/op
+BenchmarkFieldMapDiveWithKeysFailureParallel-8                	 3000000	       446 ns/op	     721 B/op	      21 allocs/op
+BenchmarkFieldCustomTypeSuccess-8                             	10000000	       211 ns/op	      32 B/op	       2 allocs/op
+BenchmarkFieldCustomTypeSuccessParallel-8                     	20000000	        65.9 ns/op	      32 B/op	       2 allocs/op
+BenchmarkFieldCustomTypeFailure-8                             	 5000000	       270 ns/op	     208 B/op	       4 allocs/op
+BenchmarkFieldCustomTypeFailureParallel-8                     	20000000	        93.3 ns/op	     208 B/op	       4 allocs/op
+BenchmarkFieldOrTagSuccess-8                                  	 2000000	       729 ns/op	      16 B/op	       1 allocs/op
+BenchmarkFieldOrTagSuccessParallel-8                          	 5000000	       367 ns/op	      16 B/op	       1 allocs/op
+BenchmarkFieldOrTagFailure-8                                  	 3000000	       472 ns/op	     224 B/op	       5 allocs/op
+BenchmarkFieldOrTagFailureParallel-8                          	 5000000	       373 ns/op	     224 B/op	       5 allocs/op
+BenchmarkStructLevelValidationSuccess-8                       	10000000	       201 ns/op	      32 B/op	       2 allocs/op
+BenchmarkStructLevelValidationSuccessParallel-8               	20000000	        66.3 ns/op	      32 B/op	       2 allocs/op
+BenchmarkStructLevelValidationFailure-8                       	 3000000	       468 ns/op	     304 B/op	       8 allocs/op
+BenchmarkStructLevelValidationFailureParallel-8               	10000000	       172 ns/op	     304 B/op	       8 allocs/op
+BenchmarkStructSimpleCustomTypeSuccess-8                      	 5000000	       376 ns/op	      32 B/op	       2 allocs/op
+BenchmarkStructSimpleCustomTypeSuccessParallel-8              	20000000	       126 ns/op	      32 B/op	       2 allocs/op
+BenchmarkStructSimpleCustomTypeFailure-8                      	 2000000	       646 ns/op	     424 B/op	       9 allocs/op
+BenchmarkStructSimpleCustomTypeFailureParallel-8              	10000000	       240 ns/op	     440 B/op	      10 allocs/op
+BenchmarkStructFilteredSuccess-8                              	 3000000	       582 ns/op	     288 B/op	       9 allocs/op
+BenchmarkStructFilteredSuccessParallel-8                      	10000000	       198 ns/op	     288 B/op	       9 allocs/op
+BenchmarkStructFilteredFailure-8                              	 3000000	       447 ns/op	     256 B/op	       7 allocs/op
+BenchmarkStructFilteredFailureParallel-8                      	10000000	       156 ns/op	     256 B/op	       7 allocs/op
+BenchmarkStructPartialSuccess-8                               	 3000000	       536 ns/op	     256 B/op	       6 allocs/op
+BenchmarkStructPartialSuccessParallel-8                       	10000000	       175 ns/op	     256 B/op	       6 allocs/op
+BenchmarkStructPartialFailure-8                               	 2000000	       738 ns/op	     480 B/op	      11 allocs/op
+BenchmarkStructPartialFailureParallel-8                       	 5000000	       256 ns/op	     480 B/op	      11 allocs/op
+BenchmarkStructExceptSuccess-8                                	 2000000	       835 ns/op	     496 B/op	      12 allocs/op
 BenchmarkStructExceptSuccessParallel-8                        	10000000	       163 ns/op	     240 B/op	       5 allocs/op
-BenchmarkStructExceptFailure-8                                	 2000000	       734 ns/op	     464 B/op	      10 allocs/op
-BenchmarkStructExceptFailureParallel-8                        	 5000000	       259 ns/op	     464 B/op	      10 allocs/op
-BenchmarkStructSimpleCrossFieldSuccess-8                      	 3000000	       432 ns/op	      72 B/op	       3 allocs/op
-BenchmarkStructSimpleCrossFieldSuccessParallel-8              	10000000	       129 ns/op	      72 B/op	       3 allocs/op
-BenchmarkStructSimpleCrossFieldFailure-8                      	 2000000	       671 ns/op	     304 B/op	       8 allocs/op
-BenchmarkStructSimpleCrossFieldFailureParallel-8              	10000000	       229 ns/op	     304 B/op	       8 allocs/op
-BenchmarkStructSimpleCrossStructCrossFieldSuccess-8           	 2000000	       628 ns/op	      80 B/op	       4 allocs/op
-BenchmarkStructSimpleCrossStructCrossFieldSuccessParallel-8   	10000000	       182 ns/op	      80 B/op	       4 allocs/op
-BenchmarkStructSimpleCrossStructCrossFieldFailure-8           	 2000000	       872 ns/op	     320 B/op	       9 allocs/op
-BenchmarkStructSimpleCrossStructCrossFieldFailureParallel-8   	 5000000	       267 ns/op	     320 B/op	       9 allocs/op
-BenchmarkStructSimpleSuccess-8                                	 5000000	       274 ns/op	       0 B/op	       0 allocs/op
-BenchmarkStructSimpleSuccessParallel-8                        	20000000	        79.0 ns/op	       0 B/op	       0 allocs/op
-BenchmarkStructSimpleFailure-8                                	 2000000	       647 ns/op	     424 B/op	       9 allocs/op
-BenchmarkStructSimpleFailureParallel-8                        	10000000	       224 ns/op	     424 B/op	       9 allocs/op
-BenchmarkStructComplexSuccess-8                               	 1000000	      1557 ns/op	     128 B/op	       8 allocs/op
-BenchmarkStructComplexSuccessParallel-8                       	 3000000	       473 ns/op	     128 B/op	       8 allocs/op
-BenchmarkStructComplexFailure-8                               	  300000	      4373 ns/op	    3041 B/op	      53 allocs/op
-BenchmarkStructComplexFailureParallel-8                       	 1000000	      1554 ns/op	    3041 B/op	      53 allocs/op
+BenchmarkStructExceptFailure-8                                	 2000000	       682 ns/op	     464 B/op	      10 allocs/op
+BenchmarkStructExceptFailureParallel-8                        	10000000	       244 ns/op	     464 B/op	      10 allocs/op
+BenchmarkStructSimpleCrossFieldSuccess-8                      	 5000000	       392 ns/op	      72 B/op	       3 allocs/op
+BenchmarkStructSimpleCrossFieldSuccessParallel-8              	20000000	       126 ns/op	      72 B/op	       3 allocs/op
+BenchmarkStructSimpleCrossFieldFailure-8                      	 2000000	       611 ns/op	     304 B/op	       8 allocs/op
+BenchmarkStructSimpleCrossFieldFailureParallel-8              	10000000	       214 ns/op	     304 B/op	       8 allocs/op
+BenchmarkStructSimpleCrossStructCrossFieldSuccess-8           	 3000000	       567 ns/op	      80 B/op	       4 allocs/op
+BenchmarkStructSimpleCrossStructCrossFieldSuccessParallel-8   	10000000	       177 ns/op	      80 B/op	       4 allocs/op
+BenchmarkStructSimpleCrossStructCrossFieldFailure-8           	 2000000	       807 ns/op	     320 B/op	       9 allocs/op
+BenchmarkStructSimpleCrossStructCrossFieldFailureParallel-8   	 5000000	       268 ns/op	     320 B/op	       9 allocs/op
+BenchmarkStructSimpleSuccess-8                                	 5000000	       256 ns/op	       0 B/op	       0 allocs/op
+BenchmarkStructSimpleSuccessParallel-8                        	20000000	        76.3 ns/op	       0 B/op	       0 allocs/op
+BenchmarkStructSimpleFailure-8                                	 2000000	       625 ns/op	     424 B/op	       9 allocs/op
+BenchmarkStructSimpleFailureParallel-8                        	10000000	       219 ns/op	     424 B/op	       9 allocs/op
+BenchmarkStructComplexSuccess-8                               	 1000000	      1431 ns/op	     128 B/op	       8 allocs/op
+BenchmarkStructComplexSuccessParallel-8                       	 3000000	       427 ns/op	     128 B/op	       8 allocs/op
+BenchmarkStructComplexFailure-8                               	  300000	      4065 ns/op	    3041 B/op	      53 allocs/op
+BenchmarkStructComplexFailureParallel-8                       	 1000000	      1478 ns/op	    3041 B/op	      53 allocs/op
 ```
 
 Complementary Software

_examples/dive/main.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"fmt"
+
+	"gopkg.in/go-playground/validator.v9"
+)
+
+// Test ...
+type Test struct {
+	Array []string          `validate:"required,gt=0,dive,required"`
+	Map   map[string]string `validate:"required,gt=0,dive,keys,keymax,endkeys,required,max=1000"`
+}
+
+// use a single instance of Validate, it caches struct info
+var validate *validator.Validate
+
+func main() {
+
+	validate = validator.New()
+
+	// registering alias so we can see the differences between
+	// map key, value validation errors
+	validate.RegisterAlias("keymax", "max=10")
+
+	var test Test
+
+	val(test)
+
+	test.Array = []string{""}
+	test.Map = map[string]string{"test > than 10": ""}
+	val(test)
+}
+
+func val(test Test) {
+	fmt.Println("testing")
+	err := validate.Struct(test)
+	fmt.Println(err)
+}

baked_in.go

@@ -32,6 +32,8 @@ func wrapFunc(fn Func) FuncCtx {
 var (
 	restrictedTags = map[string]struct{}{
 		diveTag:           {},
+		keysTag:           {},
+		endKeysTag:        {},
 		structOnlyTag:     {},
 		omitempty:         {},
 		skipValidationTag: {},

benchmarks_test.go

@@ -59,7 +59,7 @@ func BenchmarkFieldFailureParallel(b *testing.B) {
 	})
 }
 
-func BenchmarkFieldDiveSuccess(b *testing.B) {
+func BenchmarkFieldArrayDiveSuccess(b *testing.B) {
 
 	validate := New()
 
@@ -72,7 +72,7 @@ func BenchmarkFieldDiveSuccess(b *testing.B) {
 	}
 }
 
-func BenchmarkFieldDiveSuccessParallel(b *testing.B) {
+func BenchmarkFieldArrayDiveSuccessParallel(b *testing.B) {
 
 	validate := New()
 
@@ -86,7 +86,7 @@ func BenchmarkFieldDiveSuccessParallel(b *testing.B) {
 	})
 }
 
-func BenchmarkFieldDiveFailure(b *testing.B) {
+func BenchmarkFieldArrayDiveFailure(b *testing.B) {
 
 	validate := New()
 
@@ -98,7 +98,7 @@ func BenchmarkFieldDiveFailure(b *testing.B) {
 	}
 }
 
-func BenchmarkFieldDiveFailureParallel(b *testing.B) {
+func BenchmarkFieldArrayDiveFailureParallel(b *testing.B) {
 
 	validate := New()
 
@@ -112,6 +112,112 @@ func BenchmarkFieldDiveFailureParallel(b *testing.B) {
 	})
 }
 
+func BenchmarkFieldMapDiveSuccess(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"val1": "val1", "val2": "val2", "val3": "val3"}
+
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		validate.Var(m, "required,dive,required")
+	}
+}
+
+func BenchmarkFieldMapDiveSuccessParallel(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"val1": "val1", "val2": "val2", "val3": "val3"}
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			validate.Var(m, "required,dive,required")
+		}
+	})
+}
+
+func BenchmarkFieldMapDiveFailure(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"": "", "val3": "val3"}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		validate.Var(m, "required,dive,required")
+	}
+}
+
+func BenchmarkFieldMapDiveFailureParallel(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"": "", "val3": "val3"}
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			validate.Var(m, "required,dive,required")
+		}
+	})
+}
+
+func BenchmarkFieldMapDiveWithKeysSuccess(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"val1": "val1", "val2": "val2", "val3": "val3"}
+
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		validate.Var(m, "required,dive,keys,required,endkeys,required")
+	}
+}
+
+func BenchmarkFieldMapDiveWithKeysSuccessParallel(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"val1": "val1", "val2": "val2", "val3": "val3"}
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			validate.Var(m, "required,dive,keys,required,endkeys,required")
+		}
+	})
+}
+
+func BenchmarkFieldMapDiveWithKeysFailure(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"": "", "val3": "val3"}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		validate.Var(m, "required,dive,keys,required,endkeys,required")
+	}
+}
+
+func BenchmarkFieldMapDiveWithKeysFailureParallel(b *testing.B) {
+
+	validate := New()
+
+	m := map[string]string{"": "", "val3": "val3"}
+
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			validate.Var(m, "required,dive,keys,required,endkeys,required")
+		}
+	})
+}
+
 func BenchmarkFieldCustomTypeSuccess(b *testing.B) {
 
 	validate := New()

cache.go

@@ -18,11 +18,14 @@ const (
 	typeStructOnly
 	typeDive
 	typeOr
+	typeKeys
+	typeEndKeys
 )
 
 const (
 	invalidValidation   = "Invalid validation tag on field '%s'"
 	undefinedValidation = "Undefined validation function '%s' on field '%s'"
+	keysTagNotDefined   = "'" + endKeysTag + "' tag encountered without a corresponding '" + keysTag + "' tag"
 )
 
 type structCache struct {
@@ -88,11 +91,12 @@ type cTag struct {
 	aliasTag       string
 	actualAliasTag string
 	param          string
-	hasAlias       bool
 	typeof         tagType
+	keys           *cTag // only populated when using tag's 'keys' and 'endkeys' for map key validation
+	next           *cTag
 	hasTag         bool
+	hasAlias       bool
 	fn             FuncCtx
-	next           *cTag
 }
 
 func (v *Validate) extractStructCache(current reflect.Value, sName string) *cStruct {
@@ -185,7 +189,6 @@ func (v *Validate) parseFieldTagsRecursive(tag string, fieldName string, alias s
 
 		// check map for alias and process new tags, otherwise process as usual
 		if tagsVal, found := v.aliases[t]; found {
-
 			if i == 0 {
 				firstCtag, current = v.parseFieldTagsRecursive(tagsVal, fieldName, t, true)
 			} else {
@@ -197,10 +200,13 @@ func (v *Validate) parseFieldTagsRecursive(tag string, fieldName string, alias s
 			continue
 		}
 
+		var prevTag tagType
+
 		if i == 0 {
 			current = &cTag{aliasTag: alias, hasAlias: hasAlias, hasTag: true}
 			firstCtag = current
 		} else {
+			prevTag = current.typeof
 			current.next = &cTag{aliasTag: alias, hasAlias: hasAlias, hasTag: true}
 			current = current.next
 		}
@@ -211,6 +217,44 @@ func (v *Validate) parseFieldTagsRecursive(tag string, fieldName string, alias s
 			current.typeof = typeDive
 			continue
 
+		case keysTag:
+			current.typeof = typeKeys
+
+			if i == 0 || prevTag != typeDive {
+				panic(fmt.Sprintf("'%s' tag must be immediately preceeded by the '%s' tag", keysTag, diveTag))
+			}
+
+			current.typeof = typeKeys
+
+			// need to pass along only keys tag
+			// need to increment i to skip over the keys tags
+			b := make([]byte, 0, 64)
+
+			i++
+
+			for ; i < len(tags); i++ {
+
+				b = append(b, tags[i]...)
+				b = append(b, ',')
+
+				if tags[i] == endKeysTag {
+					break
+				}
+			}
+
+			current.keys, _ = v.parseFieldTagsRecursive(string(b[:len(b)-1]), fieldName, "", false)
+			continue
+
+		case endKeysTag:
+			current.typeof = typeEndKeys
+
+			// if there are more in tags then there was no keysTag defined
+			// and an error should be thrown
+			if i != len(tags)-1 {
+				panic(keysTagNotDefined)
+			}
+			return
+
 		case omitempty:
 			current.typeof = typeOmitEmpty
 			continue

doc.go

@@ -193,7 +193,8 @@ Dive
 This tells the validator to dive into a slice, array or map and validate that
 level of the slice, array or map with the validation tags that follow.
 Multidimensional nesting is also supported, each level you wish to dive will
-require another dive tag.
+require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see
+the Keys & EndKeys section just below.
 
 	Usage: dive
 
@@ -211,6 +212,30 @@ Example #2
 	// []string will be spared validation
 	// required will be applied to string
 
+Keys & EndKeys
+
+These are to be used together directly after the dive tag and tells the validator
+that anything between 'keys' and 'endkeys' applies to the keys of a map and not the
+values; think of it like the 'dive' tag, but for map keys instead of values.
+Multidimensional nesting is also supported, each level you wish to validate will
+require another 'keys' and 'endkeys' tag. These tags are only valid for maps.
+
+	Usage: dive,keys,othertagvalidation(s),endkeys,valuevalidationtags
+
+Example #1
+
+	map[string]string with validation tag "gt=0,dive,keys,eg=1|eq=2,endkeys,required"
+	// gt=0 will be applied to the map itself
+	// eg=1|eq=2 will be applied to the map keys
+	// required will be applied to map values
+
+Example #2
+
+	map[[2]string]string with validation tag "gt=0,dive,keys,dive,eq=1|eq=2,endkeys,required"
+	// gt=0 will be applied to the map itself
+	// eg=1|eq=2 will be applied to each array element in the the map keys
+	// required will be applied to map values
+
 Required
 
 This validates that the value is not the data types default zero value.

validator.go

@@ -260,6 +260,9 @@ OUTER:
 			ct = ct.next
 			continue
 
+		case typeEndKeys:
+			return
+
 		case typeDive:
 
 			ct = ct.next
@@ -294,7 +297,6 @@ OUTER:
 
 						reusableCF.altName = string(v.misc)
 					}
-
 					v.traverseField(ctx, parent, current.Index(i), ns, structNs, reusableCF, ct)
 				}
 
@@ -325,7 +327,15 @@ OUTER:
 						reusableCF.altName = string(v.misc)
 					}
 
-					v.traverseField(ctx, parent, current.MapIndex(key), ns, structNs, reusableCF, ct)
+					if ct != nil && ct.typeof == typeKeys && ct.keys != nil {
+						v.traverseField(ctx, parent, key, ns, structNs, reusableCF, ct.keys)
+						// can be nil when just keys being validated
+						if ct.next != nil {
+							v.traverseField(ctx, parent, current.MapIndex(key), ns, structNs, reusableCF, ct.next)
+						}
+					} else {
+						v.traverseField(ctx, parent, current.MapIndex(key), ns, structNs, reusableCF, ct)
+					}
 				}
 
 			default:

validator_instance.go

@@ -25,6 +25,8 @@ const (
 	isdefault          = "isdefault"
 	skipValidationTag  = "-"
 	diveTag            = "dive"
+	keysTag            = "keys"
+	endKeysTag         = "endkeys"
 	requiredTag        = "required"
 	namespaceSeparator = "."
 	leftBracket        = "["

validator_test.go

@@ -12,12 +12,11 @@ import (
 	"testing"
 	"time"
 
-	. "gopkg.in/go-playground/assert.v1"
-
 	"github.com/go-playground/locales/en"
 	"github.com/go-playground/locales/fr"
 	"github.com/go-playground/locales/nl"
 	ut "github.com/go-playground/universal-translator"
+	. "gopkg.in/go-playground/assert.v1"
 )
 
 // NOTES:
@@ -128,6 +127,26 @@ func AssertError(t *testing.T, err error, nsKey, structNsKey, field, structField
 	EqualSkip(t, 2, fe.Tag(), expectedTag)
 }
 
+func AssertDeepError(t *testing.T, err error, nsKey, structNsKey, field, structField, expectedTag, actualTag string) {
+	errs := err.(ValidationErrors)
+
+	found := false
+	var fe FieldError
+
+	for i := 0; i < len(errs); i++ {
+		if errs[i].Namespace() == nsKey && errs[i].StructNamespace() == structNsKey && errs[i].Tag() == expectedTag && errs[i].ActualTag() == actualTag {
+			found = true
+			fe = errs[i]
+			break
+		}
+	}
+
+	EqualSkip(t, 2, found, true)
+	NotEqualSkip(t, 2, fe, nil)
+	EqualSkip(t, 2, fe.Field(), field)
+	EqualSkip(t, 2, fe.StructField(), structField)
+}
+
 func getError(err error, nsKey, structNsKey string) FieldError {
 
 	errs := err.(ValidationErrors)
@@ -7313,3 +7332,238 @@ func TestUniqueValidation(t *testing.T) {
 	}
 	PanicMatches(t, func() { validate.Var(1.0, "unique") }, "Bad field type float64")
 }
+
+func TestKeys(t *testing.T) {
+
+	type Test struct {
+		Test1 map[string]string `validate:"gt=0,dive,keys,eq=testkey,endkeys,eq=testval" json:"test1"`
+		Test2 map[int]int       `validate:"gt=0,dive,keys,eq=3,endkeys,eq=4"             json:"test2"`
+		Test3 map[int]int       `validate:"gt=0,dive,keys,eq=3,endkeys"                  json:"test3"`
+	}
+
+	var tst Test
+
+	validate := New()
+	err := validate.Struct(tst)
+	NotEqual(t, err, nil)
+	Equal(t, len(err.(ValidationErrors)), 3)
+	AssertError(t, err.(ValidationErrors), "Test.Test1", "Test.Test1", "Test1", "Test1", "gt")
+	AssertError(t, err.(ValidationErrors), "Test.Test2", "Test.Test2", "Test2", "Test2", "gt")
+	AssertError(t, err.(ValidationErrors), "Test.Test3", "Test.Test3", "Test3", "Test3", "gt")
+
+	tst.Test1 = map[string]string{
+		"testkey": "testval",
+	}
+
+	tst.Test2 = map[int]int{
+		3: 4,
+	}
+
+	tst.Test3 = map[int]int{
+		3: 4,
+	}
+
+	err = validate.Struct(tst)
+	Equal(t, err, nil)
+
+	tst.Test1["badtestkey"] = "badtestvalue"
+	tst.Test2[10] = 11
+
+	err = validate.Struct(tst)
+	NotEqual(t, err, nil)
+
+	errs := err.(ValidationErrors)
+
+	Equal(t, len(errs), 4)
+
+	AssertDeepError(t, errs, "Test.Test1[badtestkey]", "Test.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.Test1[badtestkey]", "Test.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.Test2[10]", "Test.Test2[10]", "Test2[10]", "Test2[10]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.Test2[10]", "Test.Test2[10]", "Test2[10]", "Test2[10]", "eq", "eq")
+
+	type Test2 struct {
+		NestedKeys map[[1]string]string `validate:"gt=0,dive,keys,dive,eq=innertestkey,endkeys,eq=outertestval"`
+	}
+
+	var tst2 Test2
+
+	err = validate.Struct(tst2)
+	NotEqual(t, err, nil)
+	Equal(t, len(err.(ValidationErrors)), 1)
+	AssertError(t, err.(ValidationErrors), "Test2.NestedKeys", "Test2.NestedKeys", "NestedKeys", "NestedKeys", "gt")
+
+	tst2.NestedKeys = map[[1]string]string{
+		[1]string{"innertestkey"}: "outertestval",
+	}
+
+	err = validate.Struct(tst2)
+	Equal(t, err, nil)
+
+	tst2.NestedKeys[[1]string{"badtestkey"}] = "badtestvalue"
+
+	err = validate.Struct(tst2)
+	NotEqual(t, err, nil)
+
+	errs = err.(ValidationErrors)
+
+	Equal(t, len(errs), 2)
+	AssertDeepError(t, errs, "Test2.NestedKeys[[badtestkey]][0]", "Test2.NestedKeys[[badtestkey]][0]", "NestedKeys[[badtestkey]][0]", "NestedKeys[[badtestkey]][0]", "eq", "eq")
+	AssertDeepError(t, errs, "Test2.NestedKeys[[badtestkey]]", "Test2.NestedKeys[[badtestkey]]", "NestedKeys[[badtestkey]]", "NestedKeys[[badtestkey]]", "eq", "eq")
+
+	// test bad tag definitions
+
+	PanicMatches(t, func() { validate.Var(map[string]string{"key": "val"}, "endkeys,dive,eq=val") }, "'endkeys' tag encountered without a corresponding 'keys' tag")
+	PanicMatches(t, func() { validate.Var(1, "keys,eq=1,endkeys") }, "'keys' tag must be immediately preceeded by the 'dive' tag")
+
+	// test custom tag name
+	validate = New()
+	validate.RegisterTagNameFunc(func(fld reflect.StructField) string {
+		name := strings.SplitN(fld.Tag.Get("json"), ",", 2)[0]
+
+		if name == "-" {
+			return ""
+		}
+		return name
+	})
+
+	err = validate.Struct(tst)
+	NotEqual(t, err, nil)
+
+	errs = err.(ValidationErrors)
+
+	Equal(t, len(errs), 4)
+
+	AssertDeepError(t, errs, "Test.test1[badtestkey]", "Test.Test1[badtestkey]", "test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.test1[badtestkey]", "Test.Test1[badtestkey]", "test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.test2[10]", "Test.Test2[10]", "test2[10]", "Test2[10]", "eq", "eq")
+	AssertDeepError(t, errs, "Test.test2[10]", "Test.Test2[10]", "test2[10]", "Test2[10]", "eq", "eq")
+}
+
+// Thanks @adrian-sgn specific test for your specific scenario
+func TestKeysCustomValidation(t *testing.T) {
+
+	type LangCode string
+	type Label map[LangCode]string
+
+	type TestMapStructPtr struct {
+		Label Label `validate:"dive,keys,lang_code,endkeys,required"`
+	}
+
+	validate := New()
+	validate.RegisterValidation("lang_code", func(fl FieldLevel) bool {
+		validLangCodes := map[LangCode]struct{}{
+			"en": {},
+			"es": {},
+			"pt": {},
+		}
+
+		_, ok := validLangCodes[fl.Field().Interface().(LangCode)]
+		return ok
+	})
+
+	label := Label{
+		"en":  "Good morning!",
+		"pt":  "",
+		"es":  "¡Buenos días!",
+		"xx":  "Bad key",
+		"xxx": "",
+	}
+
+	err := validate.Struct(TestMapStructPtr{label})
+	NotEqual(t, err, nil)
+
+	errs := err.(ValidationErrors)
+	Equal(t, len(errs), 4)
+
+	AssertDeepError(t, errs, "TestMapStructPtr.Label[xx]", "TestMapStructPtr.Label[xx]", "Label[xx]", "Label[xx]", "lang_code", "lang_code")
+	AssertDeepError(t, errs, "TestMapStructPtr.Label[pt]", "TestMapStructPtr.Label[pt]", "Label[pt]", "Label[pt]", "required", "required")
+	AssertDeepError(t, errs, "TestMapStructPtr.Label[xxx]", "TestMapStructPtr.Label[xxx]", "Label[xxx]", "Label[xxx]", "lang_code", "lang_code")
+	AssertDeepError(t, errs, "TestMapStructPtr.Label[xxx]", "TestMapStructPtr.Label[xxx]", "Label[xxx]", "Label[xxx]", "required", "required")
+
+	// find specific error
+
+	var e FieldError
+	for _, e = range errs {
+		if e.Namespace() == "TestMapStructPtr.Label[xxx]" {
+			break
+		}
+	}
+
+	Equal(t, e.Param(), "")
+	Equal(t, e.Value().(LangCode), LangCode("xxx"))
+
+	for _, e = range errs {
+		if e.Namespace() == "TestMapStructPtr.Label[xxx]" && e.Tag() == "required" {
+			break
+		}
+	}
+
+	Equal(t, e.Param(), "")
+	Equal(t, e.Value().(string), "")
+}
+
+func TestKeyOrs(t *testing.T) {
+
+	type Test struct {
+		Test1 map[string]string `validate:"gt=0,dive,keys,eq=testkey|eq=testkeyok,endkeys,eq=testval" json:"test1"`
+	}
+
+	var tst Test
+
+	validate := New()
+	err := validate.Struct(tst)
+	NotEqual(t, err, nil)
+	Equal(t, len(err.(ValidationErrors)), 1)
+	AssertError(t, err.(ValidationErrors), "Test.Test1", "Test.Test1", "Test1", "Test1", "gt")
+
+	tst.Test1 = map[string]string{
+		"testkey": "testval",
+	}
+
+	err = validate.Struct(tst)
+	Equal(t, err, nil)
+
+	tst.Test1["badtestkey"] = "badtestval"
+
+	err = validate.Struct(tst)
+	NotEqual(t, err, nil)
+
+	errs := err.(ValidationErrors)
+
+	Equal(t, len(errs), 2)
+
+	AssertDeepError(t, errs, "Test.Test1[badtestkey]", "Test.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "eq=testkey|eq=testkeyok", "eq=testkey|eq=testkeyok")
+	AssertDeepError(t, errs, "Test.Test1[badtestkey]", "Test.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+
+	validate.RegisterAlias("okkey", "eq=testkey|eq=testkeyok")
+
+	type Test2 struct {
+		Test1 map[string]string `validate:"gt=0,dive,keys,okkey,endkeys,eq=testval" json:"test1"`
+	}
+
+	var tst2 Test2
+
+	err = validate.Struct(tst2)
+	NotEqual(t, err, nil)
+	Equal(t, len(err.(ValidationErrors)), 1)
+	AssertError(t, err.(ValidationErrors), "Test2.Test1", "Test2.Test1", "Test1", "Test1", "gt")
+
+	tst2.Test1 = map[string]string{
+		"testkey": "testval",
+	}
+
+	err = validate.Struct(tst2)
+	Equal(t, err, nil)
+
+	tst2.Test1["badtestkey"] = "badtestval"
+
+	err = validate.Struct(tst2)
+	NotEqual(t, err, nil)
+
+	errs = err.(ValidationErrors)
+
+	Equal(t, len(errs), 2)
+
+	AssertDeepError(t, errs, "Test2.Test1[badtestkey]", "Test2.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "okkey", "eq=testkey|eq=testkeyok")
+	AssertDeepError(t, errs, "Test2.Test1[badtestkey]", "Test2.Test1[badtestkey]", "Test1[badtestkey]", "Test1[badtestkey]", "eq", "eq")
+}