[pkg/telemetryquerylanguage] Add Join factory

pkg/telemetryquerylanguage/functions/tqlcommon/README.md

@@ -3,13 +3,32 @@
 The following functions can be used in any implementation of the Telemetry Query Language.  Although they are tested using [pdata](https://github.com/open-telemetry/opentelemetry-collector/tree/main/pdata) for convenience, the function implementation only interact with native Go types or types defined in the [tql package](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/pkg/telemetryquerylanguage/tql).
 
 Factory Functions
+- [Join](#join)
 - [IsMatch](#ismatch)
 
 Functions
 - [set](#set)
 - [replace_match](#replace_match)
 - [replace_pattern](#replace_pattern)
 
+## Join
+
+`Join(delimiter, ...values)`
+
+The `Join` factory function takes a delimiter and a sequence of values and concatenates their string representation. Unsupported values, such as lists or maps that may substantially increase payload size, are not added to the resulting string.
+
+`delimiter` is a string value that is used to join the string. If no delimiter is desired, then simply pass an empty string.
+
+`values` is a series of values passed as arguments. It supports paths, primitive values, and byte slices (such as trace IDs or span IDs).
+
+Examples:
+
+- `Join(": ", attributes["http.method"], attributes["http.path"])`
+
+- `Join(" ", name, 1)`
+
+- `Join("", "HTTP method is: ", attributes["http.method"])`
+
 ## IsMatch
 
 `IsMatch(target, pattern)`

pkg/telemetryquerylanguage/functions/tqlcommon/func_join.go

@@ -0,0 +1,49 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tqlcommon // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/telemetryquerylanguage/functions/tqlcommon"
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/telemetryquerylanguage/tql"
+)
+
+func Join(delimiter string, vals []tql.Getter) (tql.ExprFunc, error) {
+	return func(ctx tql.TransformContext) interface{} {
+		builder := strings.Builder{}
+		for i, rv := range vals {
+			switch val := rv.Get(ctx).(type) {
+			case string:
+				builder.WriteString(val)
+			case []byte:
+				builder.WriteString(fmt.Sprintf("%x", val))
+			case int64:
+				builder.WriteString(fmt.Sprint(val))
+			case float64:
+				builder.WriteString(fmt.Sprint(val))
+			case bool:
+				builder.WriteString(fmt.Sprint(val))
+			case nil:
+				builder.WriteString(fmt.Sprint(val))
+			}
+
+			if i != len(vals)-1 {
+				builder.WriteString(delimiter)
+			}
+		}
+		return builder.String()
+	}, nil
+}

pkg/telemetryquerylanguage/functions/tqlcommon/func_join_test.go

@@ -0,0 +1,244 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tqlcommon
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/telemetryquerylanguage/tql"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/telemetryquerylanguage/tql/tqltest"
+)
+
+func Test_join(t *testing.T) {
+	tests := []struct {
+		name      string
+		delimiter string
+		vals      []tql.StandardGetSetter
+		expected  string
+	}{
+		{
+			name:      "join strings",
+			delimiter: " ",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "world"
+					},
+				},
+			},
+			expected: "hello world",
+		},
+		{
+			name:      "nil",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return nil
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "world"
+					},
+				},
+			},
+			expected: "hello<nil>world",
+		},
+		{
+			name:      "integers",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return int64(1)
+					},
+				},
+			},
+			expected: "hello1",
+		},
+		{
+			name:      "floats",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return 3.14159
+					},
+				},
+			},
+			expected: "hello3.14159",
+		},
+		{
+			name:      "booleans",
+			delimiter: " ",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return true
+					},
+				},
+			},
+			expected: "hello true",
+		},
+		{
+			name:      "byte slices",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return []byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0xd2, 0xe6, 0x3c, 0xbe, 0x71, 0xf5, 0xa8}
+					},
+				},
+			},
+			expected: "00000000000000000ed2e63cbe71f5a8",
+		},
+		{
+			name:      "non-byte slices",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return []int64{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
+					},
+				},
+			},
+			expected: "",
+		},
+		{
+			name:      "maps",
+			delimiter: "",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return map[string]string{"key": "value"}
+					},
+				},
+			},
+			expected: "",
+		},
+		{
+			name:      "unprintable value in the middle",
+			delimiter: "-",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return map[string]string{"key": "value"}
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "world"
+					},
+				},
+			},
+			expected: "hello--world",
+		},
+		{
+			name:      "empty string values",
+			delimiter: "__",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return ""
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return ""
+					},
+				},
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return ""
+					},
+				},
+			},
+			expected: "____",
+		},
+		{
+			name:      "single argument",
+			delimiter: "-",
+			vals: []tql.StandardGetSetter{
+				{
+					Getter: func(ctx tql.TransformContext) interface{} {
+						return "hello"
+					},
+				},
+			},
+			expected: "hello",
+		},
+		{
+			name:      "no arguments",
+			delimiter: "-",
+			vals:      []tql.StandardGetSetter{},
+			expected:  "",
+		},
+		{
+			name:      "no arguments with an empty delimiter",
+			delimiter: "",
+			vals:      []tql.StandardGetSetter{},
+			expected:  "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctx := tqltest.TestTransformContext{}
+
+			getters := make([]tql.Getter, len(tt.vals))
+
+			for i, val := range tt.vals {
+				getters[i] = val
+			}
+
+			exprFunc, _ := Join(tt.delimiter, getters)
+			actual := exprFunc(ctx)
+
+			assert.Equal(t, tt.expected, actual)
+		})
+	}
+}

unreleased/add-join-factory.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/telemetryquerylanguage
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add `Join`, which allows joining an arbitrary number of strings with a delimiter
+
+# One or more tracking issues related to the change
+issues: [12476]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: