Add consul_config_entry datasource (#318)

I'm not updating the docs in this pull request as I will switch the
whole provider to use terraform-plugin-docs in
#309. I will
update the documentation after merging this PR.

Closes #317

consul/data_source_consul_config_entry.go

@@ -0,0 +1,74 @@
+package consul
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
+)
+
+func dataSourceConsulConfigEntry() *schema.Resource {
+	return &schema.Resource{
+		Read: dataSourceConsulConfigEntryRead,
+
+		Schema: map[string]*schema.Schema{
+			"kind": {
+				Type:        schema.TypeString,
+				Required:    true,
+				ForceNew:    true,
+				Description: "The kind of config entry to read.",
+			},
+
+			"name": {
+				Type:        schema.TypeString,
+				Required:    true,
+				ForceNew:    true,
+				Description: "The name of the config entry to read.",
+			},
+
+			"partition": {
+				Type:        schema.TypeString,
+				Optional:    true,
+				ForceNew:    true,
+				Description: "The partition the config entry is associated with.",
+			},
+
+			"namespace": {
+				Type:        schema.TypeString,
+				Optional:    true,
+				ForceNew:    true,
+				Description: "The namespace the config entry is associated with.",
+			},
+
+			"config_json": {
+				Type:        schema.TypeString,
+				Computed:    true,
+				Description: "The configuration of the config entry.",
+			},
+		},
+	}
+}
+
+func dataSourceConsulConfigEntryRead(d *schema.ResourceData, meta interface{}) error {
+	client, qOpts, _ := getClient(d, meta)
+
+	kind := d.Get("kind").(string)
+	name := d.Get("name").(string)
+
+	configEntry, _, err := client.ConfigEntries().Get(kind, name, qOpts)
+	if err != nil {
+		return fmt.Errorf("failed to read config entry %s/%s: %w", kind, name, err)
+	}
+
+	// Config Entries are too complex to write as maps for now so we save their JSON representation
+	data, err := configEntryToMap(configEntry)
+	if err != nil {
+		return err
+	}
+
+	d.SetId(fmt.Sprintf("%s/%s", kind, name))
+
+	sw := newStateWriter(d)
+	sw.setJson("config_json", data)
+
+	return sw.error()
+}

consul/data_source_consul_config_entry_test.go

@@ -0,0 +1,56 @@
+package consul
+
+import (
+	"regexp"
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-sdk/helper/resource"
+)
+
+func TestAccDataConsulConfigEntry_basic(t *testing.T) {
+	providers, _ := startTestServer(t)
+
+	resource.Test(t, resource.TestCase{
+		Providers: providers,
+		Steps: []resource.TestStep{
+			{
+				Config:      testAccDataConsulConfigEntryMissing,
+				ExpectError: regexp.MustCompile(`failed to read config entry service-defaults/foo: Unexpected response code: 404`),
+			},
+			{
+				Config: testAccDataConsulConfigEntry,
+				Check: resource.ComposeAggregateTestCheckFunc(
+					resource.TestCheckResourceAttr("data.consul_config_entry.read", "config_json", "{\"Expose\":{},\"MeshGateway\":{},\"Protocol\":\"https\",\"TransparentProxy\":{}}"),
+					resource.TestCheckResourceAttr("data.consul_config_entry.read", "id", "service-defaults/foo"),
+					resource.TestCheckResourceAttr("data.consul_config_entry.read", "kind", "service-defaults"),
+					resource.TestCheckResourceAttr("data.consul_config_entry.read", "name", "foo"),
+				),
+			},
+		},
+	})
+}
+
+const testAccDataConsulConfigEntry = `
+resource "consul_config_entry" "test" {
+	name = "foo"
+	kind = "service-defaults"
+
+	config_json = jsonencode({
+		MeshGateway      = {}
+		Protocol         = "https"
+		TransparentProxy = {}
+	})
+}
+
+data "consul_config_entry" "read" {
+	name = consul_config_entry.test.name
+	kind = consul_config_entry.test.kind
+}
+`
+
+const testAccDataConsulConfigEntryMissing = `
+data "consul_config_entry" "read" {
+	name = "foo"
+	kind = "service-defaults"
+}
+`

consul/resource_provider.go

@@ -162,6 +162,7 @@ func Provider() terraform.ResourceProvider {
 			"consul_network_segments":     dataSourceConsulNetworkSegments(),
 			"consul_network_area_members": dataSourceConsulNetworkAreaMembers(),
 			"consul_datacenters":          dataSourceConsulDatacenters(),
+			"consul_config_entry":         dataSourceConsulConfigEntry(),
 			"consul_peering":              dataSourceConsulPeering(),
 			"consul_peerings":             dataSourceConsulPeerings(),
 
@@ -308,7 +309,7 @@ func (sw *stateWriter) setJson(key string, value interface{}) {
 	if err != nil {
 		sw.errors = append(
 			sw.errors,
-			fmt.Sprintf("failed to marshal '%s': %v", key, err),
+			fmt.Sprintf(" - failed to marshal '%s': %v", key, err),
 		)
 		return
 	}