revert to only auto-binding engines based on block code cells (#4689)

* revert to only auto-binding engines based on block code cells
* fix tests after auto-binding change

Author: cscheid

news/changelog-1.3.md

@@ -16,6 +16,7 @@
 ## Knitr engine
 
 - Help rmarkdown find pandoc binary bundled with Quarto if none is found ([#3688](https://github.com/quarto-dev/quarto-cli/issues/3688)).
+- Do not bind knitr engine when only inline `r` expressions are found ([#3908](https://github.com/quarto-dev/quarto-cli/issues/3908)).
 
 ## Code Annotation
 

src/execute/engine.ts

@@ -130,8 +130,8 @@ export function markdownExecutionEngine(
   }
 
   // if there is no computational engine discovered then bind
-  // to the knitr engine if there are inline r expressions
-  return engineForMarkdownWithNoLanguages(markdown);
+  // to the markdown engine;
+  return markdownEngine;
 }
 
 /**
@@ -209,14 +209,6 @@ export async function fileExecutionEngineAndTarget(
   };
 }
 
-function engineForMarkdownWithNoLanguages(markdown: string) {
-  if (markdown.match(/`r[ #]([^`]+)\s*`/)) {
-    return knitrEngine;
-  } else {
-    return markdownEngine;
-  }
-}
-
 export function engineIgnoreDirs() {
   const ignoreDirs: string[] = ["node_modules"];
   executionEngines().forEach((name) => {

tests/docs/engine/_includes-r-statements.qmd

@@ -1 +1,7 @@
-An inline r value `r 7 * 11 * 13`.
+An inline r value `r 7 * 11 * 13`.
+
+As of 2023-03-07, we only auto-bind code blocks.
+
+```{r}
+3 + 4
+```

tests/docs/scholar/generated-bib.qmd

@@ -29,6 +29,7 @@ citation:
   collection-title: foo
   keyword: 'foo, bar'
 bibliography: "`r 'references.bib'`"
+engine: knitr
 ---
 
 ## this is a test document

tests/docs/smoke-all/2023/02/22/generated-bib.qmd

@@ -29,6 +29,7 @@ citation:
   collection-title: foo
   keyword: 'foo, bar'
 bibliography: "`r 'references.bib'`"
+engine: knitr
 ---
 
 ## this is a test document