Restore user agent append logic, add tests.

Restore the logic that adds a user agent when an environment variable is
set; apparently Terraform Cloud uses that. Also, add some tests to
demonstrate what results we'll get in various scenarios.

Author: paddycarver

helper/schema/provider.go

@@ -5,7 +5,9 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"os"
 	"sort"
+	"strings"
 
 	"github.com/hashicorp/go-multierror"
 
@@ -15,6 +17,8 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 )
 
+const uaEnvVar = "TF_APPEND_USER_AGENT"
+
 var ReservedProviderFields = []string{
 	"alias",
 	"version",
@@ -433,6 +437,25 @@ func (p *Provider) DataSources() []terraform.DataSource {
 // version of Terraform, the Plugin SDK, and the provider used to generate the
 // request. `name` should be the hyphen-separated reporting name of the
 // provider, and `version` should be the version of the provider.
+//
+// If TF_APPEND_USER_AGENT is set, its value will be appended to the returned
+// string.
 func (p *Provider) UserAgent(name, version string) string {
-	return fmt.Sprintf("Terraform/%s (+https://www.terraform.io) Terraform-Plugin-SDK/%s %s/%s", p.TerraformVersion, meta.SDKVersionString(), name, version)
+	ua := fmt.Sprintf("Terraform/%s (+https://www.terraform.io) Terraform-Plugin-SDK/%s", p.TerraformVersion, meta.SDKVersionString())
+	if name != "" {
+		ua += " " + name
+		if version != "" {
+			ua += "/" + version
+		}
+	}
+
+	if add := os.Getenv(uaEnvVar); add != "" {
+		add = strings.TrimSpace(add)
+		if len(add) > 0 {
+			ua += " " + add
+			log.Printf("[DEBUG] Using modified User-Agent: %s", ua)
+		}
+	}
+
+	return ua
 }

helper/schema/provider_test.go

@@ -3,6 +3,7 @@ package schema
 import (
 	"context"
 	"fmt"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -14,6 +15,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/internal/configs/configschema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/internal/diagutils"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/meta"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 )
 
@@ -780,3 +782,48 @@ func TestProvider_InternalValidate(t *testing.T) {
 		}
 	}
 }
+
+func TestProviderUserAgentAppendViaEnvVar(t *testing.T) {
+	if oldenv, isSet := os.LookupEnv(uaEnvVar); isSet {
+		defer os.Setenv(uaEnvVar, oldenv)
+	} else {
+		defer os.Unsetenv(uaEnvVar)
+	}
+
+	expectedBase := "Terraform/4.5.6 (+https://www.terraform.io) Terraform-Plugin-SDK/" + meta.SDKVersionString()
+
+	testCases := []struct {
+		providerName    string
+		providerVersion string
+		envVarValue     string
+		expected        string
+	}{
+		{"", "", "", expectedBase},
+		{"", "", " ", expectedBase},
+		{"", "", " \n", expectedBase},
+		{"", "", "test/1", expectedBase + " test/1"},
+		{"", "", "test/1 (comment)", expectedBase + " test/1 (comment)"},
+		{"My-Provider", "", "", expectedBase + " My-Provider"},
+		{"My-Provider", "", " ", expectedBase + " My-Provider"},
+		{"My-Provider", "", " \n", expectedBase + " My-Provider"},
+		{"My-Provider", "", "test/1", expectedBase + " My-Provider test/1"},
+		{"My-Provider", "", "test/1 (comment)", expectedBase + " My-Provider test/1 (comment)"},
+		{"My-Provider", "1.2.3", "", expectedBase + " My-Provider/1.2.3"},
+		{"My-Provider", "1.2.3", " ", expectedBase + " My-Provider/1.2.3"},
+		{"My-Provider", "1.2.3", " \n", expectedBase + " My-Provider/1.2.3"},
+		{"My-Provider", "1.2.3", "test/1", expectedBase + " My-Provider/1.2.3 test/1"},
+		{"My-Provider", "1.2.3", "test/1 (comment)", expectedBase + " My-Provider/1.2.3 test/1 (comment)"},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			os.Unsetenv(uaEnvVar)
+			os.Setenv(uaEnvVar, tc.envVarValue)
+			p := &Provider{TerraformVersion: "4.5.6"}
+			givenUA := p.UserAgent(tc.providerName, tc.providerVersion)
+			if givenUA != tc.expected {
+				t.Fatalf("Expected User-Agent '%s' does not match '%s'", tc.expected, givenUA)
+			}
+		})
+	}
+}