Change doc parsing to only read YAML header

Fixes unintended YAML decode errors when a documents has a valid header
but the rest of its contents are not valid YAML.

3 files changed, 25 insertions, 5 deletions

diff --git a/pkg/index/filters.go b/pkg/index/filters.go
index 7766b4c..a439185 100644
--- a/pkg/index/filters.go
+++ b/pkg/index/filters.go
@@ -65,6 +65,11 @@ var YamlHeaderFilter = DocFilter{
 }
 
 func yamlHeaderFilterFunc(_ infoPath, r io.ReadSeeker) bool {
+	return yamlHeaderPos(r) > 0
+}
+
+// Position of the end of a yaml header, negative
+func yamlHeaderPos(r io.ReadSeeker) int64 {
 	const bufSize = 4096
 	buf := make([]byte, bufSize)
 
@@ -72,9 +77,10 @@ func yamlHeaderFilterFunc(_ infoPath, r io.ReadSeeker) bool {
 	cmp := make([]byte, 4)
 	n, err := r.Read(carry)
 	if err != nil || n < 4 || string(carry) != "---\n" {
-		return false
+		return -1
 	}
 
+	pos := int64(3)
 	headerFound := false
 	readMore := true
 	for readMore {
@@ -83,12 +89,13 @@ func yamlHeaderFilterFunc(_ infoPath, r io.ReadSeeker) bool {
 		if err == io.EOF {
 			readMore = false
 		} else if err != nil {
-			return false
+			return -1
 		}
 		buf = buf[:n]
 
 		// PERF: the carry doesn't need to be checked on the first loop iteration
 		for i := range min(4, n) {
+			pos++
 			b := carry[i]
 			for j := range 4 {
 				if i+j < 4 {
@@ -104,6 +111,7 @@ func yamlHeaderFilterFunc(_ infoPath, r io.ReadSeeker) bool {
 			}
 		}
 		for i := range n - 4 {
+			pos++
 			b := buf[i]
 			if b == '\n' && string(buf[i:i+5]) == "\n---\n" {
 				headerFound = true
@@ -119,7 +127,11 @@ func yamlHeaderFilterFunc(_ infoPath, r io.ReadSeeker) bool {
 		}
 	}
 
-	return headerFound
+	if headerFound {
+		return pos
+	} else {
+		return -1
+	}
 }
 
 func DefaultFilters() []DocFilter {
diff --git a/pkg/index/index.go b/pkg/index/index.go
index 15a5e86..5d23e14 100644
--- a/pkg/index/index.go
+++ b/pkg/index/index.go
@@ -329,7 +329,14 @@ func ParseDoc(path string) (*Document, error) {
 	}
 	doc.FileTime = info.ModTime()
 
-	if err := yaml.NewDecoder(f).Decode(doc); err != nil {
+	pos := yamlHeaderPos(f)
+	f.Seek(0, io.SeekStart)
+	if pos < 0 {
+		return nil, fmt.Errorf("Can't find YAML header in %s", path)
+	}
+
+	// FIXME: decoder reads past yaml header into document
+	if err := yaml.NewDecoder(io.LimitReader(f, pos)).Decode(doc); err != nil {
 		return nil, errors.Join(ErrHeaderParse, err)
 	}
 
diff --git a/pkg/index/index_test.go b/pkg/index/index_test.go
index 4bf49e3..4e55325 100644
--- a/pkg/index/index_test.go
+++ b/pkg/index/index_test.go
@@ -193,7 +193,7 @@ func TestIndex_ParseOne(t *testing.T) {
 				f, path := newTestFile(t, "date")
 				defer f.Close()
 
-				f.WriteString("---\ndate: May 1, 2025")
+				f.WriteString("---\ndate: May 1, 2025\n---\n")
 
 				return path
 			},
@@ -266,6 +266,7 @@ func TestIndex_ParseOne(t *testing.T) {
 
 			if !errors.Is(gotErr, tt.wantErr) {
 				t.Errorf("Recieved unexpected error: want %v got %v", tt.wantErr, gotErr)
+				return
 			} else if gotErr != nil {
 				return
 			}