Retain labels is actually either a boolean or a number.

src/compare/diff.rs

@@ -77,6 +77,7 @@ use crate::types::RadioTarget;
 use crate::types::RegularLink;
 use crate::types::RepeaterType;
 use crate::types::RepeaterWarningDelayValueType;
+use crate::types::RetainLabels;
 use crate::types::Section;
 use crate::types::SpecialBlock;
 use crate::types::SrcBlock;
@@ -1625,13 +1626,45 @@ fn compare_example_block<'b, 's>(
     }
 
     // Compare retain-labels
-    let retain_labels: Option<CharOffsetInLine> = get_property_numeric(emacs, ":retain-labels")?;
-    if retain_labels != rust.retain_labels {
-        this_status = DiffStatus::Bad;
-        message = Some(format!(
-            "Retain labels mismatch (emacs != rust) {:?} != {:?}",
-            retain_labels, rust.retain_labels
-        ));
+    // retain-labels is t by default, nil if -r is set, or a number if -k is set.
+    let retain_labels = get_property_unquoted_atom(emacs, ":retain-labels")?;
+    if let Some(retain_labels) = retain_labels {
+        if retain_labels == "t" {
+            match rust.retain_labels {
+                RetainLabels::Yes => {}
+                _ => {
+                    this_status = DiffStatus::Bad;
+                    message = Some(format!(
+                        "Retain labels mismatch (emacs != rust) {:?} != {:?}",
+                        retain_labels, rust.retain_labels
+                    ));
+                }
+            }
+        } else {
+            let retain_labels: CharOffsetInLine = get_property_numeric(emacs, ":retain-labels")?.expect("Cannot be None or else the earlier get_property_unquoted_atom would have been None.");
+            match (retain_labels, &rust.retain_labels) {
+                (e, RetainLabels::Keep(r)) if e == *r => {}
+                _ => {
+                    this_status = DiffStatus::Bad;
+                    message = Some(format!(
+                        "Retain labels mismatch (emacs != rust) {:?} != {:?}",
+                        retain_labels, rust.retain_labels
+                    ));
+                }
+            }
+            // foo
+        }
+    } else {
+        match rust.retain_labels {
+            RetainLabels::No => {}
+            _ => {
+                this_status = DiffStatus::Bad;
+                message = Some(format!(
+                    "Retain labels mismatch (emacs != rust) {:?} != {:?}",
+                    retain_labels, rust.retain_labels
+                ));
+            }
+        }
     }
 
     // Compare use-labels

src/parser/lesser_block.rs

@@ -38,6 +38,7 @@ use crate::types::ExportBlock;
 use crate::types::LineNumber;
 use crate::types::Object;
 use crate::types::PlainText;
+use crate::types::RetainLabels;
 use crate::types::SrcBlock;
 use crate::types::SwitchNumberLines;
 use crate::types::VerseBlock;
@@ -168,7 +169,7 @@ pub(crate) fn example_block<'b, 'g, 'r, 's>(
                 parameters.label_format,
             )
         } else {
-            (None, None, None, true, None)
+            (None, None, RetainLabels::Yes, true, None)
         }
     };
     Ok((
@@ -331,7 +332,7 @@ fn _lesser_block_begin<'b, 'g, 'r, 's, 'c>(
 struct ExampleSwitches<'s> {
     source: &'s str,
     number_lines: Option<SwitchNumberLines>,
-    retain_labels: Option<CharOffsetInLine>,
+    retain_labels: RetainLabels,
     use_labels: bool,
     label_format: Option<&'s str>,
 }
@@ -347,7 +348,7 @@ enum SwitchState {
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
 fn example_switches<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSwitches<'s>> {
     let mut number_lines = None;
-    let mut retain_labels = None;
+    let mut retain_labels = RetainLabels::Yes;
     let mut use_labels = true;
     let mut label_format = None;
     let (remaining, (source, (words, _))) =
@@ -366,6 +367,12 @@ fn example_switches<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSwitc
                 }
                 (SwitchState::Normal, "-r") => {
                     use_labels = false;
+                    match retain_labels {
+                        RetainLabels::Yes => {
+                            retain_labels = RetainLabels::No;
+                        }
+                        _ => {}
+                    }
                 }
                 (SwitchState::Normal, "-l") => {
                     state = SwitchState::LabelFormat;
@@ -375,7 +382,7 @@ fn example_switches<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSwitc
                     let character_offset = Into::<&str>::into(text_until_flag).chars().count();
                     let character_offset = CharOffsetInLine::try_from(character_offset)
                         .expect("Character offset should fit in CharOffsetInLine");
-                    retain_labels = Some(character_offset);
+                    retain_labels = RetainLabels::Keep(character_offset);
                 }
                 (SwitchState::NewLineNumber, _) => {
                     let val = normalized_word.parse::<LineNumber>();

src/types/lesser_element.rs

@@ -38,13 +38,21 @@ pub struct CommentBlock<'s> {
 
 pub type CharOffsetInLine = u16;
 
+#[derive(Debug)]
+pub enum RetainLabels {
+    No,
+    Yes,
+    /// When adding -k to the switches on an example or src block, the labels are kept in the source code and links will use line numbers.
+    Keep(CharOffsetInLine),
+}
+
 #[derive(Debug)]
 pub struct ExampleBlock<'s> {
     pub source: &'s str,
     pub name: &'s str,
     pub switches: Option<&'s str>,
     pub number_lines: Option<SwitchNumberLines>,
-    pub retain_labels: Option<CharOffsetInLine>,
+    pub retain_labels: RetainLabels,
     pub use_labels: bool,
     pub label_format: Option<&'s str>,
     pub contents: String,

src/types/mod.rs

@@ -51,6 +51,7 @@ pub use lesser_element::LatexEnvironment;
 pub use lesser_element::LineNumber;
 pub use lesser_element::Paragraph;
 pub use lesser_element::Planning;
+pub use lesser_element::RetainLabels;
 pub use lesser_element::SrcBlock;
 pub use lesser_element::SwitchNumberLines;
 pub use lesser_element::TableCell;