useragent: add FromSlice function

This function accepts a slice of any value and converts to a slice of `UserAgentProduct` structs. This functionality will be used by upstream clients which accept a list of raw string content to be appended to the User-Agent header, rather than a structured object with name, version, and comment sections explicitly defined.

Author: jar-b

useragent/from.go

@@ -0,0 +1,49 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package useragent
+
+import (
+	"strings"
+
+	"github.com/hashicorp/aws-sdk-go-base/v2/internal/config"
+	"github.com/hashicorp/aws-sdk-go-base/v2/internal/slices"
+)
+
+// FromSlice applies the conversion defined in [fromString] to all elements
+// of a slice
+//
+// Slices of types which cannot assert to a string, empty string values, and string
+// values which do not match the expected `{product}/{version} ({comment})`
+// pattern (where version and comment are optional) return a zero value struct.
+func FromSlice[T any](sl []T) config.UserAgentProducts {
+	return slices.ApplyToAll(sl, func(v T) config.UserAgentProduct {
+		if s, ok := any(v).(string); ok && s != "" {
+			return fromString(s)
+		}
+		return config.UserAgentProduct{}
+	})
+}
+
+// fromString separates the provided string into the constituent parts
+// expected by the UserAgentProduct struct
+//
+// Values which do not match the expected `{product}/{version} ({comment})`
+// pattern, where version and comment are optional, return a zero value struct.
+func fromString(s string) config.UserAgentProduct {
+	parts := strings.Split(s, "/")
+	switch len(parts) {
+	case 1:
+		return config.UserAgentProduct{Name: parts[0]}
+	case 2:
+		subparts := strings.Split(parts[1], "(")
+		if len(subparts) == 2 {
+			version := strings.TrimSpace(subparts[0])
+			comment := strings.TrimSuffix(subparts[1], ")")
+			return config.UserAgentProduct{Name: parts[0], Version: version, Comment: comment}
+		}
+		return config.UserAgentProduct{Name: parts[0], Version: parts[1]}
+	}
+
+	return config.UserAgentProduct{}
+}

useragent/from_test.go

@@ -0,0 +1,116 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package useragent
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/aws-sdk-go-base/v2/internal/config"
+)
+
+func TestFromSlice(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		s    []any
+		want config.UserAgentProducts
+	}{
+		{
+			"nil",
+			nil,
+			config.UserAgentProducts{},
+		},
+		{
+			"non-string element",
+			[]any{false},
+			config.UserAgentProducts{config.UserAgentProduct{}},
+		},
+		{
+			"valid string",
+			[]any{"my-product/v1.2.3"},
+			config.UserAgentProducts{
+				config.UserAgentProduct{
+					Name:    "my-product",
+					Version: "v1.2.3",
+				},
+			},
+		},
+		{
+			"valid and invalid string",
+			[]any{"my-product/v1.2.3", "foo/bar/baz/qux"},
+			config.UserAgentProducts{
+				config.UserAgentProduct{
+					Name:    "my-product",
+					Version: "v1.2.3",
+				},
+				config.UserAgentProduct{},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := FromSlice(tt.s)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("FromSlice() = %+v, want %+v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_fromString(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		s    string
+		want config.UserAgentProduct
+	}{
+		{
+			"empty",
+			"",
+			config.UserAgentProduct{},
+		},
+		{
+			"name only",
+			"my-product",
+			config.UserAgentProduct{
+				Name: "my-product",
+			},
+		},
+		{
+			"name and version",
+			"my-product/v1.2.3",
+			config.UserAgentProduct{
+				Name:    "my-product",
+				Version: "v1.2.3",
+			},
+		},
+		{
+			"name, version, and comment",
+			"my-product/v1.2.3 (a comment)",
+			config.UserAgentProduct{
+				Name:    "my-product",
+				Version: "v1.2.3",
+				Comment: "a comment",
+			},
+		},
+		{
+			"all the slash",
+			"foo/bar/baz/qux",
+			config.UserAgentProduct{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := fromString(tt.s)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("fromString() = %+v, want %+v", got, tt.want)
+			}
+		})
+	}
+}