From 7ed2a7d3b4996db795fee3a7a38487f104612f83 Mon Sep 17 00:00:00 2001
From: Mathias <mthbqv@gmail.com>
Date: Wed, 23 Sep 2026 08:12:06 +0000
Subject: [PATCH] fix(api): frontmatter parser must not misparse indented list
 items as keys (#135)

Co-authored-by: Mathias <mthbqv@gmail.com>
---
 ingestion/internal/api/frontmatter.go      | 23 +++++++++++++--
 ingestion/internal/api/frontmatter_test.go | 34 ++++++++++++++++++++++
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/ingestion/internal/api/frontmatter.go b/ingestion/internal/api/frontmatter.go
index 6569f15..6177161 100644
--- a/ingestion/internal/api/frontmatter.go
+++ b/ingestion/internal/api/frontmatter.go
@@ -40,6 +40,15 @@ func parseFrontmatter(src string) (frontmatter, string) {
 	body := rest[end+len("\n---\n"):]
 
 	for _, line := range strings.Split(block, "\n") {
+		// An indented line is a continuation (a YAML block-list item, a
+		// wrapped value) never a top-level key, regardless of whether it
+		// happens to contain a colon — "  - 'Chapter 3: The Reckoning'" is
+		// not a key named "- 'Chapter 3" (hyperguild#128). Checked before
+		// Cut so a colon inside one never reaches the key/value path.
+		if line != "" && (line[0] == ' ' || line[0] == '\t') {
+			fm.lines = append(fm.lines, fmLine{raw: line})
+			continue
+		}
 		key, val, ok := strings.Cut(line, ":")
 		key = strings.TrimSpace(key)
 		if !ok || key == "" || strings.HasPrefix(strings.TrimSpace(line), "#") {
@@ -83,9 +92,19 @@ func (f *frontmatter) render() string {
 	var b strings.Builder
 	b.WriteString("---\n")
 	for _, l := range f.lines {
-		if l.key == "" {
+		switch {
+		case l.key == "":
 			b.WriteString(l.raw)
-		} else {
+		case l.value == "":
+			// A key with nothing after the colon (the YAML block-list
+			// shape: "aliases:" followed by indented "- item" lines on
+			// their own raw lines) must stay bare — "key: " with a
+			// trailing space is a different byte sequence than the
+			// original, and this type's whole purpose (see the package
+			// doc) is a byte-preserving round-trip.
+			b.WriteString(l.key)
+			b.WriteByte(':')
+		default:
 			b.WriteString(l.key)
 			b.WriteString(": ")
 			b.WriteString(l.value)
diff --git a/ingestion/internal/api/frontmatter_test.go b/ingestion/internal/api/frontmatter_test.go
index 6bcb2e3..b125f25 100644
--- a/ingestion/internal/api/frontmatter_test.go
+++ b/ingestion/internal/api/frontmatter_test.go
@@ -59,3 +59,37 @@ func TestFrontmatterRenderRoundTrips(t *testing.T) {
 	fm, _ := parseFrontmatter(src)
 	assert.Equal(t, src, fm.render())
 }
+
+func TestParseFrontmatterIndentedListItemWithColonIsNotMisparsedAsKey(t *testing.T) {
+	// hyperguild#128: an indented YAML block-list item that happens to
+	// contain a colon (e.g. a title with a subtitle) is a continuation
+	// line, never a top-level key — strings.Cut doesn't know that just
+	// because TrimSpace(key) happens to be non-empty. Misparsing it as a
+	// key/value pair and re-rendering strips its indentation, de-indenting
+	// it out of the list it belongs to. Same bug class already found and
+	// fixed in the sibling internal/wiki package's parseFrontmatterBlock
+	// (hyperguild#126 review round 3) — this package was the original the
+	// reimplementation was modeled on and had the gap too.
+	src := "---\naliases:\n  - 'Chapter 3: The Reckoning'\ntitle: 'X'\n---\nbody\n"
+	fm, _ := parseFrontmatter(src)
+	fm.set("updated_at", "2026-09-23T00:00:00Z")
+
+	out := fm.render()
+	assert.Contains(t, out, "  - 'Chapter 3: The Reckoning'",
+		"the indented list item must survive verbatim, not get re-emitted as a de-indented fake key")
+	assert.NotContains(t, out, "\n- 'Chapter 3",
+		"must not be split into a fake key/value pair at column 0 (as opposed to surviving indented, asserted above)")
+}
+
+func TestFrontmatterRenderEmptyValueKeyStaysBareNoTrailingSpace(t *testing.T) {
+	// Companion to the indented-list-item fix: "aliases:" (a key with
+	// nothing after the colon, the YAML block-list header) must round-trip
+	// bare, not as "aliases: " with a trailing space — a different byte
+	// sequence than the original, breaking this type's whole reason for
+	// being a line-preserving view rather than a YAML re-marshal.
+	// render() returns only the frontmatter block (see
+	// TestFrontmatterRenderRoundTrips), no trailing body.
+	src := "---\naliases:\n  - one\n  - two\n---\n"
+	fm, _ := parseFrontmatter(src)
+	assert.Equal(t, src, fm.render())
+}