[pkg/ottl] Add ParseKeyValue function (open-telemetry#31035)

**Description:** <Describe what has changed.>
Adds a `ParseKeyValue` converter function that parses out key values
pairs into a `pcommon.Map`. It takes a `StringGetter` target argument
and 2 optional arguments for the pair delimiter and key value delimiter.
This is an adaptation of the Stanza Key Value Parser operator to provide
feature parity.

Given the following input string `"k1=v1 k2=v2 k3=v3"`, the function
would return the following map:
```
{ "k1": "v1", "k2": "v2", "k3": "v3" }
```

**Link to tracking Issue:** <Issue number if applicable>
Closes open-telemetry#30998 

**Testing:** <Describe what testing was performed and which tests were
added.>
Added unit tests and e2e test.

**Documentation:** <Describe the documentation added.>
Added function documentation.

.chloggen/pkg-ottl-add-parse-key-value-function.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# 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/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add `ParseKeyValue` function for parsing key value pairs from a target string
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [30998]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

internal/coreinternal/parseutils/doc.go

@@ -0,0 +1,4 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package parseutils // import "github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/parseutils"

internal/coreinternal/parseutils/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package parseutils
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}

internal/coreinternal/parseutils/parser.go

@@ -0,0 +1,73 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package parseutils // import "github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/parseutils"
+
+import (
+	"fmt"
+	"strings"
+
+	"go.uber.org/multierr"
+)
+
+// SplitString will split the input on the delimiter and return the resulting slice while respecting quotes. Outer quotes are stripped.
+// Use in place of `strings.Split` when quotes need to be respected.
+// Requires `delimiter` not be an empty string
+func SplitString(input, delimiter string) ([]string, error) {
+	var result []string
+	current := ""
+	delimiterLength := len(delimiter)
+	quoteChar := "" // "" means we are not in quotes
+
+	for i := 0; i < len(input); i++ {
+		if quoteChar == "" && i+delimiterLength <= len(input) && input[i:i+delimiterLength] == delimiter { // delimiter
+			if current == "" { // leading || trailing delimiter; ignore
+				i += delimiterLength - 1
+				continue
+			}
+			result = append(result, current)
+			current = ""
+			i += delimiterLength - 1
+			continue
+		}
+
+		if quoteChar == "" && (input[i] == '"' || input[i] == '\'') { // start of quote
+			quoteChar = string(input[i])
+			continue
+		}
+		if string(input[i]) == quoteChar { // end of quote
+			quoteChar = ""
+			continue
+		}
+
+		current += string(input[i])
+	}
+
+	if quoteChar != "" { // check for closed quotes
+		return nil, fmt.Errorf("never reached the end of a quoted value")
+	}
+	if current != "" { // avoid adding empty value bc of a trailing delimiter
+		return append(result, current), nil
+	}
+
+	return result, nil
+}
+
+// ParseKeyValuePairs will split each string in `pairs` on the `delimiter` into a key and value string that get added to a map and returned.
+func ParseKeyValuePairs(pairs []string, delimiter string) (map[string]any, error) {
+	parsed := make(map[string]any)
+	var err error
+	for _, p := range pairs {
+		pair := strings.SplitN(p, delimiter, 2)
+		if len(pair) != 2 {
+			err = multierr.Append(err, fmt.Errorf("cannot split %q into 2 items, got %d item(s)", p, len(pair)))
+			continue
+		}
+
+		key := strings.TrimSpace(pair[0])
+		value := strings.TrimSpace(pair[1])
+
+		parsed[key] = value
+	}
+	return parsed, err
+}

internal/coreinternal/parseutils/parser_test.go

@@ -0,0 +1,276 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package parseutils
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_SplitString(t *testing.T) {
+	testCases := []struct {
+		name        string
+		input       string
+		delimiter   string
+		expected    []string
+		expectedErr error
+	}{
+		{
+			name:      "simple",
+			input:     "a b c",
+			delimiter: " ",
+			expected: []string{
+				"a",
+				"b",
+				"c",
+			},
+		},
+		{
+			name:      "single quotes",
+			input:     "a 'b c d'",
+			delimiter: " ",
+			expected: []string{
+				"a",
+				"b c d",
+			},
+		},
+		{
+			name:      "double quotes",
+			input:     `a " b c " d`,
+			delimiter: " ",
+			expected: []string{
+				"a",
+				" b c ",
+				"d",
+			},
+		},
+		{
+			name:      "multi-char delimiter",
+			input:     "abc!@!  def !@! g",
+			delimiter: "!@!",
+			expected: []string{
+				"abc",
+				"  def ",
+				" g",
+			},
+		},
+		{
+			name:      "leading and trailing delimiters",
+			input:     "   name=ottl        func=key_value   hello=world ",
+			delimiter: " ",
+			expected: []string{
+				"name=ottl",
+				"func=key_value",
+				"hello=world",
+			},
+		},
+		{
+			name:      "embedded double quotes in single quoted value",
+			input:     `ab c='this is a "co ol" value'`,
+			delimiter: " ",
+			expected: []string{
+				"ab",
+				`c=this is a "co ol" value`,
+			},
+		},
+		{
+			name:      "embedded double quotes end single quoted value",
+			input:     `ab c='this is a "co ol"'`,
+			delimiter: " ",
+			expected: []string{
+				"ab",
+				`c=this is a "co ol"`,
+			},
+		},
+		{
+			name:      "quoted values include whitespace",
+			input:     `name="    ottl " func="  key_ value"`,
+			delimiter: " ",
+			expected: []string{
+				"name=    ottl ",
+				"func=  key_ value",
+			},
+		},
+		{
+			name:      "delimiter longer than input",
+			input:     "abc",
+			delimiter: "aaaa",
+			expected: []string{
+				"abc",
+			},
+		},
+		{
+			name:      "delimiter not found",
+			input:     "a b c",
+			delimiter: "!",
+			expected: []string{
+				"a b c",
+			},
+		},
+		{
+			name: "newlines in input",
+			input: `a
+b
+c`,
+			delimiter: " ",
+			expected: []string{
+				"a\nb\nc",
+			},
+		},
+		{
+			name: "newline delimiter",
+			input: `a b c
+d e f
+g 
+h`,
+			delimiter: "\n",
+			expected: []string{
+				"a b c",
+				"d e f",
+				"g ",
+				"h",
+			},
+		},
+		{
+			name:      "empty input",
+			input:     "",
+			delimiter: " ",
+			expected:  nil,
+		},
+		{
+			name:      "equal input and delimiter",
+			input:     "abc",
+			delimiter: "abc",
+			expected:  nil,
+		},
+		{
+			name:        "unclosed quotes",
+			input:       "a 'b c",
+			delimiter:   " ",
+			expectedErr: fmt.Errorf("never reached the end of a quoted value"),
+		},
+		{
+			name:        "mismatched quotes",
+			input:       `a 'b c' "d '`,
+			delimiter:   " ",
+			expectedErr: fmt.Errorf("never reached the end of a quoted value"),
+		},
+		{
+			name:      "tab delimiters",
+			input:     "a	b	c",
+			delimiter: "\t",
+			expected: []string{
+				"a",
+				"b",
+				"c",
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			result, err := SplitString(tc.input, tc.delimiter)
+
+			if tc.expectedErr == nil {
+				assert.NoError(t, err)
+				assert.Equal(t, tc.expected, result)
+			} else {
+				assert.EqualError(t, err, tc.expectedErr.Error())
+				assert.Nil(t, result)
+			}
+		})
+	}
+}
+
+func Test_ParseKeyValuePairs(t *testing.T) {
+	testCases := []struct {
+		name        string
+		pairs       []string
+		delimiter   string
+		expected    map[string]any
+		expectedErr error
+	}{
+		{
+			name:      "multiple delimiters",
+			pairs:     []string{"a==b", "c=d=", "e=f"},
+			delimiter: "=",
+			expected: map[string]any{
+				"a": "=b",
+				"c": "d=",
+				"e": "f",
+			},
+		},
+		{
+			name:        "no delimiter found",
+			pairs:       []string{"ab"},
+			delimiter:   "=",
+			expectedErr: fmt.Errorf("cannot split \"ab\" into 2 items, got 1 item(s)"),
+		},
+		{
+			name:        "no delimiter found 2x",
+			pairs:       []string{"ab", "cd"},
+			delimiter:   "=",
+			expectedErr: fmt.Errorf("cannot split \"ab\" into 2 items, got 1 item(s); cannot split \"cd\" into 2 items, got 1 item(s)"),
+		},
+		{
+			name:      "empty pairs",
+			pairs:     []string{},
+			delimiter: "=",
+			expected:  map[string]any{},
+		},
+		{
+			name:        "empty pair string",
+			pairs:       []string{""},
+			delimiter:   "=",
+			expectedErr: fmt.Errorf("cannot split \"\" into 2 items, got 1 item(s)"),
+		},
+		{
+			name:      "empty delimiter",
+			pairs:     []string{"a=b", "c=d"},
+			delimiter: "",
+			expected: map[string]any{
+				"a": "=b",
+				"c": "=d",
+			},
+		},
+		{
+			name:      "empty pairs & delimiter",
+			pairs:     []string{},
+			delimiter: "",
+			expected:  map[string]any{},
+		},
+		{
+			name:      "early delimiter",
+			pairs:     []string{"=a=b"},
+			delimiter: "=",
+			expected: map[string]any{
+				"": "a=b",
+			},
+		},
+		{
+			name:      "weird spacing",
+			pairs:     []string{"        a=   b    ", "     c       =  d "},
+			delimiter: "=",
+			expected: map[string]any{
+				"a": "b",
+				"c": "d",
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			result, err := ParseKeyValuePairs(tc.pairs, tc.delimiter)
+
+			if tc.expectedErr == nil {
+				assert.NoError(t, err)
+				assert.Equal(t, tc.expected, result)
+			} else {
+				assert.EqualError(t, err, tc.expectedErr.Error())
+			}
+		})
+	}
+}