Add --doctest-compilation-args option to allow passing arguments to doctest compilation

Author: GuillaumeGomez

src/librustdoc/config.rs

@@ -172,6 +172,9 @@ pub(crate) struct Options {
     /// This is mainly useful for other tools that reads that debuginfo to figure out
     /// how to call the compiler with the same arguments.
     pub(crate) expanded_args: Vec<String>,
+
+    /// Arguments to be used when compiling doctests.
+    pub(crate) doctest_compilation_args: Vec<String>,
 }
 
 impl fmt::Debug for Options {
@@ -774,6 +777,7 @@ impl Options {
         let scrape_examples_options = ScrapeExamplesOptions::new(matches, dcx);
         let with_examples = matches.opt_strs("with-examples");
         let call_locations = crate::scrape_examples::load_call_locations(with_examples, dcx);
+        let doctest_compilation_args = matches.opt_strs("doctest-compilation-args");
 
         let unstable_features =
             rustc_feature::UnstableFeatures::from_environment(crate_name.as_deref());
@@ -819,6 +823,7 @@ impl Options {
             scrape_examples_options,
             unstable_features,
             expanded_args: args,
+            doctest_compilation_args,
         };
         let render_options = RenderOptions {
             output,

src/librustdoc/doctest.rs

@@ -78,6 +78,17 @@ pub(crate) fn generate_args_file(file_path: &Path, options: &RustdocOptions) ->
         content.push(format!("-Z{unstable_option_str}"));
     }
 
+    for compilation_args in &options.doctest_compilation_args {
+        for flag in compilation_args
+            .split_whitespace()
+            .map(|flag| flag.trim())
+            .filter(|flag| !flag.is_empty())
+        {
+            // Very simple parsing implementation. Might be a good idea to correctly handle strings.
+            content.push(flag.to_string());
+        }
+    }
+
     let content = content.join("\n");
 
     file.write_all(content.as_bytes())

src/librustdoc/lib.rs

@@ -685,6 +685,14 @@ fn opts() -> Vec<RustcOptGroup> {
             "[rust]",
         ),
         opt(Unstable, Flag, "", "html-no-source", "Disable HTML source code pages generation", ""),
+        unstable("doctest-compilation-args", |o| {
+            o.optmulti(
+                "",
+                "doctest-compilation-args",
+                "",
+                "add arguments to be used when compiling doctests",
+            )
+        }),
     ]
 }