fmt: format load strings in tests

Signed-off-by: Michael Hoffmann <mhoffm@posteo.de>

Makefile

@@ -69,6 +69,8 @@ format: $(GOIMPORTS)
 	@echo ">> formatting go code"
 	@gofmt -s -w $(FILES_TO_FMT)
 	@$(GOIMPORTS) -w $(FILES_TO_FMT)
+	@echo ">> formatting tests"
+	@go run ci/loadvet/main.go -fix ./...
 
 .PHONY:lint
 lint: format deps $(GOLANGCI_LINT) $(FAILLINT) $(COPYRIGHT) docs

ci/loadvet/main.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/token"
+	"io"
+	"os"
+	"strings"
+	"unicode"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/singlechecker"
+)
+
+func main() {
+	singlechecker.Main(loadAnalyzer)
+}
+
+var loadAnalyzer = &analysis.Analyzer{
+	Name: "loadvet",
+	Doc:  "reports ill-formatted prometheus load directives",
+	Run:  run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	for _, file := range pass.Files {
+		if !strings.HasSuffix(file.Name.String(), "_test") {
+			continue
+		}
+		var stack []ast.Node
+		ast.Inspect(file, func(n ast.Node) bool {
+			defer func() {
+				if n == nil {
+					stack = stack[:len(stack)-1]
+				} else {
+					stack = append(stack, n)
+				}
+			}()
+			if n == nil || len(stack) == 0 {
+				return true
+			}
+			parent := stack[len(stack)-1]
+			if _, ok := parent.(*ast.KeyValueExpr); !ok {
+				return true
+			}
+
+			s, ok := n.(*ast.BasicLit)
+			if !ok {
+				return true
+			}
+			if s.Kind != token.STRING {
+				return true
+			}
+			quote := s.Value[0]
+			if quote != '`' {
+				return true
+			}
+			cont := s.Value[1 : len(s.Value)-1]
+			if !strings.HasPrefix(cont, "load") {
+				return true
+			}
+			position := pass.Fset.Position(s.Pos())
+			lineAtPosition, err := readLine(position.Filename, position.Line)
+			if err != nil {
+				return true
+			}
+			whiteSpace := leadingWhitespace(lineAtPosition)
+			if formatted := formatLoadDirective(cont, whiteSpace); cont != formatted {
+				pass.Report(analysis.Diagnostic{
+					Pos:     s.Pos(),
+					Message: "ill-formatted load directive found",
+					SuggestedFixes: []analysis.SuggestedFix{
+						{
+							Message: fmt.Sprintf("Should replace '%s' with '%s'", cont, formatted),
+							TextEdits: []analysis.TextEdit{
+								{
+									Pos:     s.Pos(),
+									End:     s.End(),
+									NewText: []byte(fmt.Sprintf("%c%s%c", quote, formatted, quote)),
+								},
+							},
+						},
+					},
+				})
+			}
+
+			return false
+		})
+	}
+	return nil, nil
+}
+
+func formatLoadDirective(load, whiteSpace string) string {
+	var res strings.Builder
+
+	sc := bufio.NewScanner(strings.NewReader(load))
+	for i := 0; sc.Scan(); i++ {
+		if i == 0 {
+			res.WriteString(sc.Text())
+		} else {
+			res.WriteString(whiteSpace)
+			res.WriteString(strings.Repeat(" ", 4))
+			res.WriteString(strings.TrimSpace(sc.Text()))
+		}
+		res.WriteByte('\n')
+	}
+
+	return strings.TrimSpace(res.String())
+}
+
+func readLine(filename string, line int) (string, error) {
+	content, err := os.ReadFile(filename)
+	if err != nil {
+		return "", err
+	}
+	sc := bufio.NewScanner(bytes.NewReader(content))
+	for i := 0; sc.Scan(); i++ {
+		if i == line-1 {
+			return sc.Text(), sc.Err()
+		}
+	}
+	return "", io.EOF
+}
+
+func leadingWhitespace(line string) string {
+	var res strings.Builder
+	for _, r := range line {
+		if unicode.IsSpace(r) {
+			res.WriteRune(r)
+		} else {
+			break
+		}
+	}
+	return res.String()
+}