validate content with StringIsNotEmpty

Signed-off-by: Nandor Kracser <bonifaido@gmail.com>

go.mod

@@ -3,7 +3,7 @@ module github.com/banzaicloud/terraform-provider-k8s
 go 1.13
 
 require (
-	github.com/hashicorp/terraform-plugin-sdk v1.4.0
+	github.com/hashicorp/terraform-plugin-sdk v1.7.0
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mitchellh/mapstructure v1.1.2
 	go.uber.org/zap v1.10.0 // indirect

go.sum

@@ -211,8 +211,12 @@ github.com/hashicorp/logutils v1.0.0 h1:dLEQVugN8vlakKOUE3ihGLTZJRB4j+M2cdTm/ORI
 github.com/hashicorp/logutils v1.0.0/go.mod h1:QIAnNjmIWmVIIkWDTG1z5v++HQmx9WQRO+LraFDTW64=
 github.com/hashicorp/terraform-config-inspect v0.0.0-20191115094559-17f92b0546e8 h1:+RyjwU+Gnd/aTJBPZVDNm903eXVjjqhbaR4Ypx3xYyY=
 github.com/hashicorp/terraform-config-inspect v0.0.0-20191115094559-17f92b0546e8/go.mod h1:p+ivJws3dpqbp1iP84+npOyAmTTOLMgCzrXd3GSdn/A=
-github.com/hashicorp/terraform-plugin-sdk v1.4.0 h1:b1LluARpES0Gq78oF4a9of3eS0iXM5JTwlt604vGvBY=
-github.com/hashicorp/terraform-plugin-sdk v1.4.0/go.mod h1:H5QLx/uhwfxBZ59Bc5SqT19M4i+fYt7LZjHTpbLZiAg=
+github.com/hashicorp/terraform-json v0.4.0 h1:KNh29iNxozP5adfUFBJ4/fWd0Cu3taGgjHB38JYqOF4=
+github.com/hashicorp/terraform-json v0.4.0/go.mod h1:eAbqb4w0pSlRmdvl8fOyHAi/+8jnkVYN28gJkSJrLhU=
+github.com/hashicorp/terraform-plugin-sdk v1.7.0 h1:B//oq0ZORG+EkVrIJy0uPGSonvmXqxSzXe8+GhknoW0=
+github.com/hashicorp/terraform-plugin-sdk v1.7.0/go.mod h1:OjgQmey5VxnPej/buEhe+YqKm0KNvV3QqU4hkqHqPCY=
+github.com/hashicorp/terraform-plugin-test v1.2.0 h1:AWFdqyfnOj04sxTdaAF57QqvW7XXrT8PseUHkbKsE8I=
+github.com/hashicorp/terraform-plugin-test v1.2.0/go.mod h1:QIJHYz8j+xJtdtLrFTlzQVC0ocr3rf/OjIpgZLK56Hs=
 github.com/hashicorp/terraform-svchost v0.0.0-20191011084731-65d371908596 h1:hjyO2JsNZUKT1ym+FAdlBEkGPevazYsmVgIMw7dVELg=
 github.com/hashicorp/terraform-svchost v0.0.0-20191011084731-65d371908596/go.mod h1:kNDNcF7sN4DocDLBkQYz73HGKwN1ANB1blq4lIYLYvg=
 github.com/hashicorp/yamux v0.0.0-20180604194846-3520598351bb/go.mod h1:+NfK9FKeTrX5uv1uIXGdwYDTeHna2qgaIlx54MXqjAM=
@@ -359,6 +363,8 @@ github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:
 github.com/zclconf/go-cty v1.0.0/go.mod h1:xnAOWiHeOqg2nWS62VtQ7pbOu17FtxJNW8RLEih+O3s=
 github.com/zclconf/go-cty v1.1.0 h1:uJwc9HiBOCpoKIObTQaLR+tsEXx1HBHnOsOOpcdhZgw=
 github.com/zclconf/go-cty v1.1.0/go.mod h1:xnAOWiHeOqg2nWS62VtQ7pbOu17FtxJNW8RLEih+O3s=
+github.com/zclconf/go-cty v1.2.1 h1:vGMsygfmeCl4Xb6OA5U5XVAaQZ69FvoG7X2jUtQujb8=
+github.com/zclconf/go-cty v1.2.1/go.mod h1:hOPWgoHbaTUnI5k4D2ld+GRpFJSCe6bCM7m1q/N4PQ8=
 github.com/zclconf/go-cty-yaml v1.0.1 h1:up11wlgAaDvlAGENcFDnZgkn0qUJurso7k6EpURKNF8=
 github.com/zclconf/go-cty-yaml v1.0.1/go.mod h1:IP3Ylp0wQpYm50IHK8OZWKMu6sPJIUgKa8XhiVHura0=
 go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=

k8s/resource_k8s_manifest.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/hashicorp/terraform-plugin-sdk/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
+	"github.com/hashicorp/terraform-plugin-sdk/helper/validation"
 	"github.com/mitchellh/mapstructure"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
@@ -37,9 +38,10 @@ func resourceK8sManifest() *schema.Resource {
 				ForceNew:  true,
 			},
 			"content": {
-				Type:      schema.TypeString,
-				Required:  true,
-				Sensitive: false,
+				Type:         schema.TypeString,
+				Required:     true,
+				Sensitive:    false,
+				ValidateFunc: validation.StringIsNotEmpty,
 			},
 			"delete_cascade": {
 				Type:      schema.TypeBool,