Fix schema being always updated

* add tests, that verify contents of the schema
* add test for Swagger/OpenAPI based schemas
* add fetching schema definition either from `value` or `definitions` based on
  content type
* add Json supress diff function, that allows ignoring insignificant changes,
  e.g. in white spaces
* use Json supress diff function when the content type is json based

azurerm/internal/services/apimanagement/api_management_api_schema_resource.go

@@ -1,6 +1,7 @@
 package apimanagement
 
 import (
+	"encoding/json"
 	"fmt"
 	"log"
 	"time"
@@ -12,6 +13,7 @@ import (
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/services/apimanagement/parse"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/services/apimanagement/schemaz"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/tf/pluginsdk"
+	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/tf/suppress"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/tf/validation"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/internal/timeouts"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/utils"
@@ -52,6 +54,12 @@ func resourceApiManagementApiSchema() *pluginsdk.Resource {
 				Type:         pluginsdk.TypeString,
 				Required:     true,
 				ValidateFunc: validation.StringIsNotEmpty,
+				DiffSuppressFunc: func(k, old, new string, d *pluginsdk.ResourceData) bool {
+					if d.Get("content_type") == "application/vnd.ms-azure-apim.swagger.definitions+json" || d.Get("content_type") == "application/vnd.oai.openapi.components+json" {
+						return suppress.JsonDiff(k, old, new, d)
+					}
+					return old == new
+				},
 			},
 		},
 	}
@@ -140,10 +148,32 @@ func resourceApiManagementApiSchemaRead(d *pluginsdk.ResourceData, meta interfac
 	if properties := resp.SchemaContractProperties; properties != nil {
 		d.Set("content_type", properties.ContentType)
 		if documentProperties := properties.SchemaDocumentProperties; documentProperties != nil {
-			d.Set("value", documentProperties.Value)
+			/*
+				As per https://docs.microsoft.com/en-us/rest/api/apimanagement/2019-12-01/api-schema/get#schemacontract
+
+				- Swagger Schema use application/vnd.ms-azure-apim.swagger.definitions+json
+				- WSDL Schema use application/vnd.ms-azure-apim.xsd+xml
+				- OpenApi Schema use application/vnd.oai.openapi.components+json
+				- WADL Schema use application/vnd.ms-azure-apim.wadl.grammars+xml.
+
+				Definitions used for Swagger/OpenAPI schemas only, otherwise Value is used
+			*/
+			if *properties.ContentType == "application/vnd.ms-azure-apim.swagger.definitions+json" || *properties.ContentType == "application/vnd.oai.openapi.components+json" {
+				if documentProperties.Definitions != nil {
+					value, err := json.Marshal(documentProperties.Definitions)
+					if err != nil {
+						return fmt.Errorf("[FATAL] Unable to serialize schema to json. Error: %+v. Schema struct: %+v", err, documentProperties.Definitions)
+					}
+					d.Set("value", string(value))
+				}
+			} else if *properties.ContentType == "application/vnd.ms-azure-apim.xsd+xml" || *properties.ContentType == "application/vnd.ms-azure-apim.wadl.grammars+xml" {
+				d.Set("value", documentProperties.Value)
+			} else {
+				return fmt.Errorf("[FATAL] Unkown content type %q for schema %q (API Management Service %q / API %q / Resource Group %q)", *properties.ContentType, schemaID, serviceName, apiName, resourceGroup)
+			}
 		}
-	}
 
+	}
 	return nil
 }
 

azurerm/internal/services/apimanagement/api_management_api_schema_resource_test.go

@@ -3,6 +3,8 @@ package apimanagement_test
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
+	"strings"
 	"testing"
 
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/helpers/azure"
@@ -19,12 +21,31 @@ type ApiManagementApiSchemaResource struct {
 func TestAccApiManagementApiSchema_basic(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_api_management_api_schema", "test")
 	r := ApiManagementApiSchemaResource{}
+	schema, _ := ioutil.ReadFile("testdata/api_management_api_schema.xml")
 
 	data.ResourceTest(t, r, []acceptance.TestStep{
 		{
 			Config: r.basic(data),
 			Check: acceptance.ComposeTestCheckFunc(
 				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("value").HasValue(string(schema)),
+			),
+		},
+		data.ImportStep(),
+	})
+}
+
+func TestAccApiManagementApiSchema_basicSwagger(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_api_management_api_schema", "test")
+	r := ApiManagementApiSchemaResource{}
+	schema, _ := ioutil.ReadFile("testdata/api_management_api_schema_swagger.json")
+
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.basicSwagger(data),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("value").HasValue(strings.TrimRight(string(schema), "\r\n")),
 			),
 		},
 		data.ImportStep(),
@@ -79,6 +100,21 @@ resource "azurerm_api_management_api_schema" "test" {
 `, r.template(data), data.RandomInteger)
 }
 
+func (r ApiManagementApiSchemaResource) basicSwagger(data acceptance.TestData) string {
+	return fmt.Sprintf(`
+%s
+
+resource "azurerm_api_management_api_schema" "test" {
+  api_name            = azurerm_api_management_api.test.name
+  api_management_name = azurerm_api_management_api.test.api_management_name
+  resource_group_name = azurerm_api_management_api.test.resource_group_name
+  schema_id           = "acctestSchema%d"
+  content_type        = "application/vnd.ms-azure-apim.swagger.definitions+json"
+  value               = file("testdata/api_management_api_schema_swagger.json")
+}
+`, r.template(data), data.RandomInteger)
+}
+
 func (r ApiManagementApiSchemaResource) requiresImport(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 %s

azurerm/internal/services/apimanagement/testdata/api_management_api_schema_swagger.json

@@ -0,0 +1 @@
+{"schema-bug-example":{"properties":{"Field2":{"description":"Field2","type":"string"},"field1":{"description":"Field1","type":"string"}},"required":["field1","Field2"],"type":"object"}}

azurerm/internal/tf/suppress/json.go

@@ -0,0 +1,21 @@
+package suppress
+
+import (
+	"encoding/json"
+	"reflect"
+
+	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
+)
+
+func JsonDiff(_, old, new string, _ *schema.ResourceData) bool {
+	if old == new {
+		return true
+	}
+	var oldJson interface{}
+	var newJson interface{}
+
+	json.Unmarshal([]byte(old), &oldJson)
+	json.Unmarshal([]byte(new), &newJson)
+
+	return reflect.DeepEqual(oldJson, newJson)
+}

azurerm/internal/tf/suppress/json_test.go

@@ -0,0 +1,39 @@
+package suppress
+
+import "testing"
+
+func TestJsonDiff(t *testing.T) {
+	cases := []struct {
+		Name     string
+		StringA  string
+		StringB  string
+		Suppress bool
+	}{
+		{
+			Name:     "empty",
+			StringA:  "",
+			StringB:  "",
+			Suppress: true,
+		},
+		{
+			Name:     "simple same object",
+			StringA:  "{\"field\": \"value\"}",
+			StringB:  "{\"field\": \"value\"}",
+			Suppress: true,
+		},
+		{
+			Name:     "simple object whitespace diff",
+			StringA:  "{\n\"field\":      \"value\"\n}",
+			StringB:  "{\"field\": \"value\"}",
+			Suppress: false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.Name, func(t *testing.T) {
+			if JsonDiff("test", tc.StringA, tc.StringB, nil) != tc.Suppress {
+				t.Fatalf("Expected JsonDiff to return %t for '%q' == '%q'", tc.Suppress, tc.StringA, tc.StringB)
+			}
+		})
+	}
+}