revealjs - code line numbers not working when set to "1"

because it was parsed as true.

Author: cderv

news/changelog-1.8.md

@@ -42,6 +42,7 @@ All changes included in 1.8:
 - ([#12598](https://github.com/quarto-dev/quarto-cli/pull/12598)): Ensure `.fragment` on an image with caption applies to whole figure.
 - ([#12716](https://github.com/quarto-dev/quarto-cli/issues/12716)): Correctly resolve `"brand"` set in `theme` configuration for document in subdirectory from project root.
 - Use `cdn.jsdelivr.net` for mathjax dependencies to ensure consistent CDN usage across formats. Previously, `cdnjs.cloudflare.com` was used for `revealjs` mathjax dependencies, while `cdn.jsdelivr.net` was used for html format.
+- [#13316](https://github.com/quarto-dev/quarto-cli/issues/13316): `code-line-numbers: "1"` correctly highlight the first line now.
 
 ### `docx`
 

src/resources/filters/quarto-pre/line-numbers.lua

@@ -26,7 +26,9 @@ end
 function lineNumbersAttribute(el)
   local default = param(constants.kCodeLineNumbers, false)
   local lineNumbers = attribute(el, constants.kCodeLineNumbers, default)
-  if lineNumbers == true or lineNumbers == "true" or lineNumbers == "1" then
+  -- format that do accept string for this attributes. "1" and "0" should not be parsed as TRUE / FALSE
+  local acceptStrings = _quarto.format.isRevealJsOutput() and not _quarto.format.isDocusaurusOutput()
+  if lineNumbers == true or lineNumbers == "true" or (lineNumbers == "1" and not acceptStrings) then
     return true
   elseif lineNumbers == false or lineNumbers == "false" or lineNumbers == "0" then
     return false

tests/docs/smoke-all/2025/09/02/13316.qmd

@@ -0,0 +1,22 @@
+---
+format: html
+_quarto:
+  tests:
+    html:
+      ensureHtmlElements:
+        - ['pre.sourceCode.number-lines']
+        - ['#cb1[data-code-line-numbers="1"]']
+    revealjs:
+      ensureHtmlElements:
+        - ['#cb1[data-code-line-numbers="1"]', 'pre.sourceCode.number-lines']
+        - []
+execute: 
+  echo: true
+---
+
+```{r}
+#| code-line-numbers: "1"
+mean(
+  c(1, 2, 3, 4, 5)
+)
+```