fix: preserve BibTeX newlines and backslashes

cmd/bibtex.go

@@ -0,0 +1,44 @@
+package cmd
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+
+	"github.com/nickng/bibtex"
+)
+
+// formatBibTeX aligns fields while preserving their contents verbatim.
+func formatBibTeX(entry *bibtex.BibEntry) string {
+	keys := make([]string, 0, len(entry.Fields))
+	width := 0
+	for key := range entry.Fields {
+		keys = append(keys, key)
+		if len(key) > width {
+			width = len(key)
+		}
+	}
+	priority := map[string]int{"title": -3, "author": -2, "url": -1}
+	sort.Slice(keys, func(i, j int) bool {
+		pi, pj := priority[keys[i]], priority[keys[j]]
+		return pi < pj || (pi == pj && keys[i] < keys[j])
+	})
+
+	var output strings.Builder
+	fmt.Fprintf(&output, "@%s{%s,\n", entry.Type, entry.CiteName)
+	for _, key := range keys {
+		value := entry.Fields[key].String()
+		if _, err := strconv.Atoi(value); err != nil {
+			// BibTeX delimiters preserve LaTeX commands and newlines; Go's %q escapes them.
+			if strings.ContainsAny(value, "\"{}") {
+				value = "{" + value + "}"
+			} else {
+				value = "\"" + value + "\""
+			}
+		}
+		fmt.Fprintf(&output, "    %-*s = %s,\n", width, key, value)
+	}
+	output.WriteString("}\n")
+	return output.String()
+}

cmd/bibtex_test.go

@@ -0,0 +1,71 @@
+package cmd
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/nickng/bibtex"
+)
+
+func TestFormatBibTeXPreservesFieldContents(t *testing.T) {
+	for _, value := range []string{
+		"A simple title",
+		"First line\n\tSecond line",
+		`Ducas, L\'eo`,
+		`10.1007/example\_23`,
+		`[2022] \copyright 2022`,
+		`Literal \n and \t commands`,
+		`A LaTeX \\ line break`,
+		`The "quoted" title`,
+		`A {nested {title}} with \alpha`,
+		"Léo and Göttingen",
+		"  leading and trailing spaces  ",
+		"",
+		"00123",
+	} {
+		t.Run(value, func(t *testing.T) {
+			entry := bibtex.NewBibEntry("article", "test")
+			entry.AddField("title", bibtex.NewBibConst(value))
+			output := formatBibTeX(entry)
+			parsed, err := bibtex.Parse(strings.NewReader(output))
+			if err != nil {
+				t.Fatalf("parse output: %v\n%s", err, output)
+			}
+			if len(parsed.Entries) != 1 {
+				t.Fatalf("output entry count = %d, want 1", len(parsed.Entries))
+			}
+			title, ok := parsed.Entries[0].Fields["title"]
+			if !ok {
+				t.Fatal("output is missing title")
+			}
+			if got := title.String(); got != value {
+				t.Errorf("title = %q, want %q", got, value)
+			}
+		})
+	}
+}
+
+func TestFormatBibTeXFieldOrderAndAlignment(t *testing.T) {
+	entry := bibtex.NewBibEntry("article", "test")
+	for key, value := range map[string]string{
+		"year":      "2022",
+		"author":    `Ducas, L\'eo`,
+		"booktitle": "{EUROCRYPT} 2022",
+		"title":     "First line\n              second line",
+		"url":       "https://example.com",
+	} {
+		entry.AddField(key, bibtex.NewBibConst(value))
+	}
+	const want = `@article{test,
+    title     = "First line
+              second line",
+    author    = "Ducas, L\'eo",
+    url       = "https://example.com",
+    booktitle = {{EUROCRYPT} 2022},
+    year      = 2022,
+}
+`
+	if got := formatBibTeX(entry); got != want {
+		t.Errorf("BibTeX output:\n%s\nwant:\n%s", got, want)
+	}
+}

cmd/hexhex.go

@@ -80,7 +80,7 @@ func runZB(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return fmt.Errorf("create BibTeX entry: %w", err)
 	}
-	if _, err := fmt.Fprint(cmd.OutOrStdout(), entry.PrettyString()); err != nil {
+	if _, err := fmt.Fprint(cmd.OutOrStdout(), formatBibTeX(entry)); err != nil {
 		return fmt.Errorf("write BibTeX entry: %w", err)
 	}
 	return nil

cmd/mr.go

@@ -76,7 +76,7 @@ func runMR(cmd *cobra.Command, args []string) error {
 	if entry == nil || entry.BibTeX == nil {
 		return fmt.Errorf("MR result %d has no BibTeX entry", selected+1)
 	}
-	if _, err := fmt.Fprint(cmd.OutOrStdout(), entry.BibTeX.PrettyString()); err != nil {
+	if _, err := fmt.Fprint(cmd.OutOrStdout(), formatBibTeX(entry.BibTeX)); err != nil {
 		return fmt.Errorf("write BibTeX entry: %w", err)
 	}
 	return nil

cmd/mr_test.go

@@ -58,6 +58,47 @@ func TestRunMRWritesOneBibTeXEntry(t *testing.T) {
 	assertMRBibTeX(t, output.String(), "MR1")
 }
 
+func TestRunMRPreservesBibTeXFields(t *testing.T) {
+	const source = `@incollection{MR4485627,
+    AUTHOR    = {Ducas, L\'eo and van Woerden, Wessel},
+    BOOKTITLE = {Advances in cryptology---{EUROCRYPT} 2022. {P}art {III}},
+    DOI       = {10.1007/978-3-031-07082-2\_23},
+    TITLE     = {On the lattice isomorphism problem, quadratic forms,
+              remarkable lattices, and cryptography},
+    YEAR      = {[2022] \copyright 2022},
+}`
+	parsed, err := bibtex.Parse(strings.NewReader(source))
+	if err != nil {
+		t.Fatalf("parse fixture: %v", err)
+	}
+	bib := parsed.Entries[0]
+	useMRQuery(t, func(string, string, string) ([]*mr.Entry, error) {
+		return []*mr.Entry{{BibTeX: bib}}, nil
+	})
+
+	command := &cobra.Command{}
+	var output bytes.Buffer
+	command.SetOut(&output)
+	if err := runMR(command, []string{"ducas", "On the lattice isomorphism problem", "-"}); err != nil {
+		t.Fatalf("runMR() error = %v", err)
+	}
+	printed, err := bibtex.Parse(strings.NewReader(output.String()))
+	if err != nil {
+		t.Fatalf("parse output: %v\n%s", err, output.String())
+	}
+	if len(printed.Entries) != 1 {
+		t.Fatalf("output entry count = %d, want 1", len(printed.Entries))
+	}
+	for key, value := range bib.Fields {
+		got, ok := printed.Entries[0].Fields[key]
+		if !ok {
+			t.Errorf("output is missing field %s", key)
+		} else if got.String() != value.String() {
+			t.Errorf("field %s = %q, want %q", key, got.String(), value.String())
+		}
+	}
+}
+
 func TestRunMRChoosesAndHandlesCancellation(t *testing.T) {
 	entries := []*mr.Entry{
 		mrTestEntry("MR1", "First result", "2025"),

cmd/phd.go

@@ -69,7 +69,7 @@ func runPhD(cmd *cobra.Command, args []string) error {
 	if bib == nil {
 		return fmt.Errorf("selected PhD result has no BibTeX entry")
 	}
-	if _, err := fmt.Fprint(cmd.OutOrStdout(), bib.PrettyString()); err != nil {
+	if _, err := fmt.Fprint(cmd.OutOrStdout(), formatBibTeX(bib)); err != nil {
 		return fmt.Errorf("write BibTeX entry: %w", err)
 	}
 	return nil