rustdoc: add --minimum-supported-rust-version option

Cargo.lock

@@ -4489,6 +4489,7 @@ dependencies = [
  "rayon",
  "regex",
  "rustdoc-json-types",
+ "semver",
  "serde",
  "serde_json",
  "smallvec",

src/librustdoc/Cargo.toml

@@ -15,6 +15,7 @@ minifier = "0.0.43"
 rayon = "1.5.1"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+semver = "1.0"
 smallvec = "1.6.1"
 tempfile = "3"
 itertools = "0.10.1"

src/librustdoc/config.rs

@@ -276,6 +276,8 @@ crate struct RenderOptions {
     crate call_locations: AllCallLocations,
     /// If `true`, Context::init will not emit shared files.
     crate no_emit_shared: bool,
+    /// Comes from the `--minimum-supported-rust-version` option.
+    crate minimum_supported_rust_version: Option<String>,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -656,6 +658,16 @@ impl Options {
         let generate_link_to_definition = matches.opt_present("generate-link-to-definition");
         let extern_html_root_takes_precedence =
             matches.opt_present("extern-html-root-takes-precedence");
+        let minimum_supported_rust_version = matches.opt_str("minimum-supported-rust-version");
+        if let Some(ref minimum_supported_rust_version) = minimum_supported_rust_version {
+            if let Err(e) = semver::Version::parse(minimum_supported_rust_version) {
+                diag.struct_err(&format!(
+                    "--minimum-supported-rust-version expects a valid semver value: {e}"
+                ))
+                .emit();
+                return Err(1);
+            }
+        }
 
         if generate_link_to_definition && (show_coverage || output_format != OutputFormat::Html) {
             diag.struct_err(
@@ -734,6 +746,7 @@ impl Options {
                 generate_link_to_definition,
                 call_locations,
                 no_emit_shared: false,
+                minimum_supported_rust_version,
             },
             crate_name,
             output_format,

src/librustdoc/html/render/context.rs

@@ -124,6 +124,8 @@ crate struct SharedContext<'tcx> {
     crate cache: Cache,
 
     crate call_locations: AllCallLocations,
+
+    crate minimum_supported_rust_version: Option<String>,
 }
 
 impl SharedContext<'_> {
@@ -406,6 +408,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             generate_link_to_definition,
             call_locations,
             no_emit_shared,
+            minimum_supported_rust_version,
             ..
         } = options;
 
@@ -490,6 +493,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             span_correspondance_map: matches,
             cache,
             call_locations,
+            minimum_supported_rust_version,
         };
 
         // Add the default themes to the `Vec` of stylepaths

src/librustdoc/html/render/mod.rs

@@ -466,15 +466,26 @@ fn document(
     item: &clean::Item,
     parent: Option<&clean::Item>,
     heading_offset: HeadingOffset,
+) {
+    document_inner(w, cx, item, parent, heading_offset, None)
+}
+
+fn document_inner(
+    w: &mut Buffer,
+    cx: &Context<'_>,
+    item: &clean::Item,
+    parent: Option<&clean::Item>,
+    heading_offset: HeadingOffset,
+    extra: Option<String>,
 ) {
     if let Some(ref name) = item.name {
         info!("Documenting {}", name);
     }
     document_item_info(w, cx, item, parent);
     if parent.is_none() {
-        document_full_collapsible(w, item, cx, heading_offset);
+        document_full_collapsible(w, item, cx, heading_offset, extra);
     } else {
-        document_full(w, item, cx, heading_offset);
+        document_full(w, item, cx, heading_offset, extra);
     }
 }
 
@@ -539,17 +550,19 @@ fn document_full_collapsible(
     item: &clean::Item,
     cx: &Context<'_>,
     heading_offset: HeadingOffset,
+    extra: Option<String>,
 ) {
-    document_full_inner(w, item, cx, true, heading_offset);
+    document_full_inner(w, item, cx, true, heading_offset, extra);
 }
 
 fn document_full(
     w: &mut Buffer,
     item: &clean::Item,
     cx: &Context<'_>,
     heading_offset: HeadingOffset,
+    extra: Option<String>,
 ) {
-    document_full_inner(w, item, cx, false, heading_offset);
+    document_full_inner(w, item, cx, false, heading_offset, extra);
 }
 
 fn document_full_inner(
@@ -558,7 +571,11 @@ fn document_full_inner(
     cx: &Context<'_>,
     is_collapsible: bool,
     heading_offset: HeadingOffset,
+    extra: Option<String>,
 ) {
+    if let Some(extra) = extra {
+        w.write_str(&extra);
+    }
     if let Some(s) = item.collapsed_doc_value() {
         debug!("Doc block: =====\n{}\n=====", s);
         if is_collapsible {
@@ -1442,7 +1459,7 @@ fn render_impl(
                         // because impls can't have a stability.
                         if item.doc_value().is_some() {
                             document_item_info(&mut info_buffer, cx, it, Some(parent));
-                            document_full(&mut doc_buffer, item, cx, HeadingOffset::H5);
+                            document_full(&mut doc_buffer, item, cx, HeadingOffset::H5, None);
                             short_documented = false;
                         } else {
                             // In case the item isn't documented,
@@ -1460,7 +1477,7 @@ fn render_impl(
                 } else {
                     document_item_info(&mut info_buffer, cx, item, Some(parent));
                     if rendering_params.show_def_docs {
-                        document_full(&mut doc_buffer, item, cx, HeadingOffset::H5);
+                        document_full(&mut doc_buffer, item, cx, HeadingOffset::H5, None);
                         short_documented = false;
                     }
                 }

src/librustdoc/html/render/print_item.rs

@@ -16,7 +16,7 @@ use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_target::abi::{Layout, Primitive, TagEncoding, Variants};
 
 use super::{
-    collect_paths_for_type, document, ensure_trailing_slash, item_ty_to_section,
+    collect_paths_for_type, document, document_inner, ensure_trailing_slash, item_ty_to_section,
     notable_traits_decl, render_assoc_item, render_assoc_items, render_attributes_in_code,
     render_attributes_in_pre, render_impl, render_stability_since_raw, write_srclink,
     AssocItemLink, Context, ImplRenderingParameters,
@@ -188,7 +188,12 @@ fn toggle_close(w: &mut Buffer) {
 }
 
 fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[clean::Item]) {
-    document(w, cx, item, None, HeadingOffset::H2);
+    if item.is_crate() {
+        let extra = cx.shared.minimum_supported_rust_version.as_ref().map(|v| format!("<div class=\"extra-info\">ⓘ The minimum supported Rust version for this crate is: <b>{}</b>.</div>", v));
+        document_inner(w, cx, item, None, HeadingOffset::H2, extra);
+    } else {
+        document(w, cx, item, None, HeadingOffset::H2);
+    }
 
     let mut indices = (0..items.len()).filter(|i| !items[*i].is_stripped()).collect::<Vec<usize>>();
 

src/librustdoc/html/static/css/rustdoc.css

@@ -581,6 +581,11 @@ h2.location a {
 	cursor: pointer;
 }
 
+.extra-info {
+	margin-bottom: 1.5rem;
+	font-size: 1.05rem;
+}
+
 .docblock-short {
 	overflow-wrap: break-word;
 	overflow-wrap: anywhere;

src/librustdoc/lib.rs

@@ -611,6 +611,14 @@ fn opts() -> Vec<RustcOptGroup> {
                 "path to function call information (for displaying examples in the documentation)",
             )
         }),
+        unstable("minimum-supported-rust-version", |o| {
+            o.optopt(
+                "",
+                "minimum-supported-rust-version",
+                "if provided, it will display the minimum supported rust version in the documentation",
+                "VERSION",
+            )
+        }),
         // deprecated / removed options
         stable("plugin-path", |o| {
             o.optmulti(

src/test/rustdoc-ui/minimum-supported-rust-version.rs

@@ -0,0 +1,3 @@
+// compile-flags:-Zunstable-options --minimum-supported-rust-version 1.48
+
+pub struct Foo;

src/test/rustdoc-ui/minimum-supported-rust-version.stderr

@@ -0,0 +1,2 @@
+error: --minimum-supported-rust-version expects a valid semver value: unexpected end of input while parsing minor version number
+

src/test/rustdoc/minimum-supported-rust-version.rs

@@ -0,0 +1,18 @@
+// compile-flags:-Zunstable-options --minimum-supported-rust-version 1.48.0
+
+#![crate_name = "foo"]
+
+// @has 'foo/index.html'
+// @has - '//*[@id="main-content"]/*[@class="extra-info"]' 'ⓘ The minimum supported Rust version for this crate is: 1.48.0.'
+// @has - '//*[@class="rustdoc-toggle top-doc"]/*[@class="docblock"]' 'This crate is awesome.'
+
+//! This crate is awesome.
+
+// We check that the minimum supported rust version is only on the crate page.
+// @has 'foo/struct.Foo.html'
+// @!has - '//*[@class="extra-info"]'
+pub struct Foo;
+
+// @has 'foo/bar/index.html'
+// @!has - '//*[@class="extra-info"]'
+pub mod bar {}