Rollup merge of #132596 - GuillaumeGomez:show-coverage, r=notriddle

[rustdoc] Fix `--show-coverage` when JSON output format is used

I realized while looking on the docs.rs page of the `sysinfo` crate that the coverage numbers displayed were wrong:

![image](https://github.com/user-attachments/assets/264b2e25-6271-4ed1-8b35-e8bd4fd475c6)

I realized that it was because `--show-coverage --output-format=json` was relying on the same logic as the JSON output for the doc generation whereas it should not. I fixed it by changing the API for querying `is_json` a bit.

The underlying issue is that JSON output format is stripping reexports of items from private modules.

r? ``@notriddle``

src/librustdoc/clean/mod.rs

@@ -2907,7 +2907,7 @@ fn clean_extern_crate<'tcx>(
                     None => false,
                 }
         })
-        && !cx.output_format.is_json();
+        && !cx.is_json_output();
 
     let krate_owner_def_id = krate.owner_id.def_id;
     if please_inline {
@@ -3000,7 +3000,7 @@ fn clean_use_statement_inner<'tcx>(
     // forcefully don't inline if this is not public or if the
     // #[doc(no_inline)] attribute is present.
     // Don't inline doc(hidden) imports so they can be stripped at a later stage.
-    let mut denied = cx.output_format.is_json()
+    let mut denied = cx.is_json_output()
         || !(visibility.is_public()
             || (cx.render_options.document_private && is_visible_from_parent_mod))
         || pub_underscore

src/librustdoc/core.rs

@@ -121,6 +121,13 @@ pub(crate) fn as_local_hir_id(tcx: TyCtxt<'_>, item_id: ItemId) -> Option<HirId>
             _ => None,
         }
     }
+
+    /// Returns `true` if the JSON output format is enabled for generating the crate content.
+    ///
+    /// If another option like `--show-coverage` is enabled, it will return `false`.
+    pub(crate) fn is_json_output(&self) -> bool {
+        self.output_format.is_json() && !self.show_coverage
+    }
 }
 
 /// Creates a new `DiagCtxt` that can be used to emit warnings and errors.

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -132,6 +132,7 @@ fn to_json(&self) -> String {
 
     fn print_results(&self) {
         let output_format = self.ctx.output_format;
+        // In this case we want to ensure that the `OutputFormat` is JSON and NOT the `DocContext`.
         if output_format.is_json() {
             println!("{}", self.to_json());
             return;

src/librustdoc/passes/strip_hidden.rs

@@ -23,7 +23,7 @@
 /// Strip items marked `#[doc(hidden)]`
 pub(crate) fn strip_hidden(krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
     let mut retained = ItemIdSet::default();
-    let is_json_output = cx.output_format.is_json() && !cx.show_coverage;
+    let is_json_output = cx.is_json_output();
 
     // strip all #[doc(hidden)] items
     let krate = {

src/librustdoc/passes/strip_priv_imports.rs

@@ -13,7 +13,7 @@
 };
 
 pub(crate) fn strip_priv_imports(krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
-    let is_json_output = cx.output_format.is_json() && !cx.show_coverage;
+    let is_json_output = cx.is_json_output();
     ImportStripper {
         tcx: cx.tcx,
         is_json_output,

src/librustdoc/passes/strip_private.rs

@@ -18,7 +18,7 @@
 pub(crate) fn strip_private(mut krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
     // This stripper collects all *retained* nodes.
     let mut retained = ItemIdSet::default();
-    let is_json_output = cx.output_format.is_json() && !cx.show_coverage;
+    let is_json_output = cx.is_json_output();
 
     // strip all private items
     {

src/librustdoc/visit_ast.rs

@@ -235,7 +235,7 @@ fn maybe_inline_local(
             return false;
         }
 
-        if self.cx.output_format.is_json() {
+        if self.cx.is_json_output() {
             return false;
         }
 

tests/rustdoc-ui/show-coverage-json.rs

@@ -0,0 +1,13 @@
+//@ compile-flags: -Z unstable-options --show-coverage --output-format=json
+//@ check-pass
+
+mod bar {
+    /// a
+    ///
+    /// ```
+    /// let x = 0;
+    /// ```
+    pub struct Foo;
+}
+
+pub use bar::Foo;

tests/rustdoc-ui/show-coverage-json.stdout

@@ -0,0 +1 @@
+{"$DIR/show-coverage-json.rs":{"total":2,"with_docs":1,"total_examples":2,"with_examples":1}}

tests/rustdoc-ui/show-coverage.rs

@@ -0,0 +1,13 @@
+//@ compile-flags: -Z unstable-options --show-coverage
+//@ check-pass
+
+mod bar {
+    /// a
+    ///
+    /// ```
+    /// let x = 0;
+    /// ```
+    pub struct Foo;
+}
+
+pub use bar::Foo;

tests/rustdoc-ui/show-coverage.stdout

@@ -0,0 +1,7 @@
++-------------------------------------+------------+------------+------------+------------+
+| File                                | Documented | Percentage |   Examples | Percentage |
++-------------------------------------+------------+------------+------------+------------+
+| ...ests/rustdoc-ui/show-coverage.rs |          1 |      50.0% |          1 |      50.0% |
++-------------------------------------+------------+------------+------------+------------+
+| Total                               |          1 |      50.0% |          1 |      50.0% |
++-------------------------------------+------------+------------+------------+------------+