chore(tools): Add metadata check to README linter (#16587)

tools/readme_linter/assert.go

@@ -15,6 +15,7 @@ type T struct {
 	markdown       []byte
 	newlineOffsets []int
 	sourceFlag     bool
+	pluginType     plugin
 
 	fails int
 }
@@ -36,6 +37,13 @@ func (t *T) assertNodef(n ast.Node, format string, args ...interface{}) {
 	t.printFailedAssertf(n, format, args...)
 }
 
+func (t *T) assertNodeLineOffsetf(n ast.Node, offset int, format string, args ...interface{}) {
+	t.printFileOffset(n, offset)
+	fmt.Printf(format+"\n", args...)
+	t.printRule(3)
+	t.fails++
+}
+
 func (t *T) assertLinef(line int, format string, args ...interface{}) {
 	// this func only exists to make the call stack to t.printRule the same depth
 	// as when called through assertf
@@ -79,14 +87,17 @@ func (t *T) line(offset int) int {
 }
 
 func (t *T) printFile(n ast.Node) {
+	t.printFileOffset(n, 0)
+}
+
+func (t *T) printFileOffset(n ast.Node, offset int) {
 	lines := n.Lines()
 	if lines == nil || lines.Len() == 0 {
 		t.printFileLine(0)
 		return
 	}
-	offset := lines.At(0).Start
+	line := t.line(lines.At(0).Start)
-	line := t.line(offset)
+	t.printFileLine(line + offset)
-	t.printFileLine(line)
 }
 
 func (t *T) printFileLine(line int) {

tools/readme_linter/main.go

@@ -16,6 +16,7 @@ import (
 
 func main() {
 	sourceFlag := flag.Bool("source", false, "include location of linter code that failed assertion")
+	quiet := flag.Bool("quiet", false, "only print failed assertion but no pass information")
 
 	flag.Parse()
 
@@ -23,7 +24,7 @@ func main() {
 	pass := true
 	for _, filename := range flag.Args() {
 		var filePass bool
-		filePass, err = checkFile(filename, guessPluginType(filename), *sourceFlag)
+		filePass, err = checkFile(filename, guessPluginType(filename), *sourceFlag, *quiet)
 		if err != nil {
 			panic(err)
 		}
@@ -46,9 +47,10 @@ func init() {
 	// Rules for all plugin types
 	all := []ruleFunc{
 		firstSection,
-		noLongLinesInParagraphs(80),
+		metadata,
 		configSection,
 		relativeTelegrafLinks,
+		noLongLinesInParagraphs(80),
 	}
 	for i := pluginInput; i <= pluginParser; i++ {
 		rules[i] = all
@@ -85,7 +87,7 @@ func init() {
 	}...)
 }
 
-func checkFile(filename string, pluginType plugin, sourceFlag bool) (bool, error) {
+func checkFile(filename string, pluginType plugin, sourceFlag, quiet bool) (bool, error) {
 	md, err := os.ReadFile(filename)
 	if err != nil {
 		return false, err
@@ -131,6 +133,7 @@ func checkFile(filename string, pluginType plugin, sourceFlag bool) (bool, error
 		markdown:       md,
 		newlineOffsets: newlineOffsets,
 		sourceFlag:     sourceFlag,
+		pluginType:     pluginType,
 	}
 	for _, rule := range rules {
 		err = rule(&tester, root)
@@ -138,7 +141,9 @@ func checkFile(filename string, pluginType plugin, sourceFlag bool) (bool, error
 			return false, err
 		}
 	}
-	tester.printPassFail()
+	if !quiet {
+		tester.printPassFail()
+	}
 
 	return tester.pass(), nil
 }

tools/readme_linter/rules.go

@@ -1,12 +1,86 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
+	"regexp"
+	"slices"
 	"strings"
 
 	"github.com/yuin/goldmark/ast"
 )
 
+var (
+	// Setup regular expression for checking versions and valid choices
+	// Matches HTML comments (e.g., <!-- some comment -->) surrounded by optional whitespace
+	metaComment = regexp.MustCompile(`(?:\s*<!-- .* -->\s*)`)
+
+	// Matches Telegraf versioning format (e.g., "Telegraf v1.2.3")
+	metaVersion = regexp.MustCompile(`^Telegraf v\d+\.\d+\.\d+(?:\s+<!-- .* -->\s*)?$`)
+
+	metaTags = map[plugin][]string{
+		pluginInput: {
+			"applications",
+			"cloud",
+			"containers",
+			"datastore",
+			"hardware",
+			"iot",
+			"logging",
+			"messaging",
+			"network",
+			"server",
+			"system",
+			"testing",
+			"web",
+		},
+		pluginOutput: {
+			"applications",
+			"cloud",
+			"containers",
+			"datastore",
+			"hardware",
+			"iot",
+			"logging",
+			"messaging",
+			"network",
+			"server",
+			"system",
+			"testing",
+			"web",
+		},
+		pluginAggregator: {
+			"math",
+			"sampling",
+			"statistics",
+			"transformation",
+		},
+		pluginProcessor: {
+			"math",
+			"sampling",
+			"statistics",
+			"transformation",
+		},
+	}
+
+	metaOSes = []string{
+		"all",
+		"freebsd",
+		"linux",
+		"macos",
+		"solaris",
+		"windows",
+	}
+
+	metaOrder = []string{
+		"introduction version",
+		"deprecation version",
+		"removal version",
+		"tags",
+		"operating systems",
+	}
+)
+
 // The first section is a heading with plugin name and paragraph short
 // description
 func firstSection(t *T, root ast.Node) error {
@@ -212,6 +286,170 @@ func relativeTelegrafLinks(t *T, root ast.Node) error {
 	return nil
 }
 
+// Each plugin should have metadata for documentation generation
+func metadata(t *T, root ast.Node) error {
+	const icons string = "⭐🚩🔥🏷️💻"
+
+	n := root.FirstChild()
+	if n == nil {
+		t.assertf("no metadata section found")
+		return nil
+	}
+
+	// Advance to the first heading which should be the plugin header
+	for n != nil {
+		if _, ok := n.(*ast.Heading); ok {
+			t.assertHeadingLevel(1, n)
+			break
+		}
+		n = n.NextSibling()
+	}
+
+	// Get the description text and check for metadata
+	positions := make([]string, 0, 5)
+	for n != nil {
+		n = n.NextSibling()
+
+		// The next heading will end the initial section
+		if _, ok := n.(*ast.Heading); ok {
+			break
+		}
+
+		// Ignore everything that is not text
+		para, ok := n.(*ast.Paragraph)
+		if !ok {
+			continue
+		}
+
+		// Metadata should be separate paragraph with the items ordered.
+		var inMetadata bool
+		var counter int
+		scanner := bufio.NewScanner(bytes.NewBuffer(para.Lines().Value(t.markdown)))
+		for scanner.Scan() {
+			txt := scanner.Text()
+			if counter == 0 {
+				inMetadata = strings.ContainsAny(txt, icons)
+			}
+			counter++
+
+			// If we are not in a metadata section, we need to make sure we don't
+			// see any metadata in this text.
+			if !inMetadata {
+				if strings.ContainsAny(txt, icons) {
+					t.assertNodeLineOffsetf(n, counter-1, "metadata found in section not surrounded by empty lines")
+					return nil
+				}
+				continue
+			}
+
+			icon, remainder, found := strings.Cut(txt, " ")
+			if !found || !strings.Contains(icons, icon) {
+				t.assertNodeLineOffsetf(n, counter-1, "metadata line must start with a valid icon and a space")
+				continue
+			}
+			if strings.ContainsAny(remainder, icons) {
+				t.assertNodeLineOffsetf(n, counter-1, "each metadata entry must be on a separate line")
+				continue
+			}
+
+			// We are in a metadata section, so test for the correct structure
+			switch icon {
+			case "⭐":
+				if !metaVersion.MatchString(remainder) {
+					t.assertNodeLineOffsetf(n, counter-1, "invalid introduction version format; has to be 'Telegraf vX.Y.Z'")
+				}
+				positions = append(positions, "introduction version")
+			case "🚩":
+				if !metaVersion.MatchString(remainder) {
+					t.assertNodeLineOffsetf(n, counter-1, "invalid deprecation version format; has to be 'Telegraf vX.Y.Z'")
+				}
+				positions = append(positions, "deprecation version")
+			case "🔥":
+				if !metaVersion.MatchString(remainder) {
+					t.assertNodeLineOffsetf(n, counter-1, "invalid removal version format; has to be 'Telegraf vX.Y.Z'")
+				}
+				positions = append(positions, "removal version")
+			case "🏷️":
+				validTags, found := metaTags[t.pluginType]
+				if !found {
+					t.assertNodeLineOffsetf(n, counter-1, "no tags expected for plugin type")
+					continue
+				}
+
+				for _, tag := range strings.Split(remainder, ",") {
+					tag = metaComment.ReplaceAllString(tag, "")
+					if !slices.Contains(validTags, strings.TrimSpace(tag)) {
+						t.assertNodeLineOffsetf(n, counter-1, "unknown tag %q", tag)
+					}
+				}
+				positions = append(positions, "tags")
+			case "💻":
+				for _, os := range strings.Split(remainder, ",") {
+					os = metaComment.ReplaceAllString(os, "")
+					if !slices.Contains(metaOSes, strings.TrimSpace(os)) {
+						t.assertNodeLineOffsetf(n, counter-1, "unknown operating system %q", os)
+					}
+				}
+				positions = append(positions, "operating systems")
+			default:
+				t.assertNodeLineOffsetf(n, counter-1, "invalid metadata icon")
+				continue
+			}
+		}
+	}
+
+	if len(positions) == 0 {
+		t.assertf("metadata is missing")
+		return nil
+	}
+
+	// Check for duplicate entries
+	seen := make(map[string]bool)
+	for _, p := range positions {
+		if seen[p] {
+			t.assertNodef(n, "duplicate metadata entry for %q", p)
+			return nil
+		}
+		seen[p] = true
+	}
+
+	// Remove the optional entries from the checklist
+	validOrder := append(make([]string, 0, len(metaOrder)), metaOrder...)
+	if !slices.Contains(positions, "deprecation version") && !slices.Contains(positions, "removal version") {
+		idx := slices.Index(validOrder, "deprecation version")
+		validOrder = slices.Delete(validOrder, idx, idx+1)
+		idx = slices.Index(validOrder, "removal version")
+		validOrder = slices.Delete(validOrder, idx, idx+1)
+	}
+	if _, found := metaTags[t.pluginType]; !found {
+		idx := slices.Index(metaOrder, "tags")
+		metaOrder = slices.Delete(metaOrder, idx, idx+1)
+	}
+
+	// Check the order of the metadata entries and required entries
+	if len(validOrder) != len(positions) {
+		for _, v := range validOrder {
+			if !slices.Contains(positions, v) {
+				t.assertNodef(n, "metadata entry for %q is missing", v)
+			}
+		}
+		return nil
+	}
+
+	for i, v := range validOrder {
+		if v != positions[i] {
+			if i == 0 {
+				t.assertNodef(n, "%q has to be the first entry", v)
+			} else {
+				t.assertNodef(n, "%q has to follow %q", v, validOrder[i-1])
+			}
+			return nil
+		}
+	}
+
+	return nil
+}
+
 // To do: Check markdown files that aren't plugin readme files for paragraphs
 // with long lines