rustdoc: add test case for modnav position when TOC is off

src/librustdoc/html/render/context.rs

@@ -15,12 +15,9 @@ use rustc_span::{sym, FileName, Symbol};
 
 use super::print_item::{full_path, item_path, print_item};
 use super::search_index::build_index;
+use super::sidebar::{print_sidebar, sidebar_module_like, ModuleLike, Sidebar};
 use super::write_shared::write_shared;
-use super::{
-    collect_spans_and_sources, scrape_examples_help,
-    sidebar::{print_sidebar, sidebar_module_like, ModuleLike, Sidebar},
-    AllTypes, LinkFromSrc, StylePath,
-};
+use super::{collect_spans_and_sources, scrape_examples_help, AllTypes, LinkFromSrc, StylePath};
 use crate::clean::types::ExternalLocation;
 use crate::clean::utils::has_doc_flag;
 use crate::clean::{self, ExternalCrate};

src/librustdoc/html/render/sidebar.rs

@@ -7,13 +7,12 @@ use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefIdSet;
 use rustc_middle::ty::{self, TyCtxt};
 
-use crate::{
-    clean,
-    formats::{item_type::ItemType, Impl},
-    html::{format::Buffer, markdown::IdMap, markdown::MarkdownWithToc},
-};
-
 use super::{item_ty_to_section, Context, ItemSection};
+use crate::clean;
+use crate::formats::item_type::ItemType;
+use crate::formats::Impl;
+use crate::html::format::Buffer;
+use crate::html::markdown::{IdMap, MarkdownWithToc};
 
 #[derive(Clone, Copy)]
 pub(crate) enum ModuleLike {

tests/rustdoc-gui/sidebar-modnav-position.goml

@@ -0,0 +1,44 @@
+// Verifies that, when TOC is hidden, modnav is always in exactly the same spot
+// This is driven by a reasonably common use case:
+//
+// - There are three or more items that might meet my needs.
+// - I open the first one, decide it's not what I want, switch to the second one using the sidebar.
+// - The second one also doesn't meet my needs, so I switch to the third.
+// - The third also doesn't meet my needs, so...
+//
+// because the sibling module nav is in exactly the same place every time,
+// it's very easy to find and switch between pages that way.
+
+go-to: "file://" + |DOC_PATH| + "/test_docs/enum.WhoLetTheDogOut.html"
+show-text: true
+set-local-storage: {"rustdoc-hide-toc": "true"}
+
+define-function: (
+    "check-positions",
+    [url],
+    block {
+        go-to: "file://" + |DOC_PATH| + |url|
+        // Checking results colors.
+        assert-position: ("#rustdoc-modnav > h2", {"x": |h2_x|, "y": |h2_y|})
+        assert-position: (
+            "#rustdoc-modnav > ul:first-of-type > li:first-of-type",
+            {"x": |x|, "y": |y|}
+        )
+    },
+)
+
+// First, at test_docs root
+go-to: "file://" + |DOC_PATH| + "/test_docs/enum.WhoLetTheDogOut.html"
+store-position: ("#rustdoc-modnav > h2", {"x": h2_x, "y": h2_y})
+store-position: ("#rustdoc-modnav > ul:first-of-type > li:first-of-type", {"x": x, "y": y})
+call-function: ("check-positions", {"url": "/test_docs/enum.WhoLetTheDogOut.html"})
+call-function: ("check-positions", {"url": "/test_docs/struct.StructWithPublicUndocumentedFields.html"})
+call-function: ("check-positions", {"url": "/test_docs/codeblock_sub/index.html"})
+
+// Now in a submodule
+go-to: "file://" + |DOC_PATH| + "/test_docs/fields/struct.Struct.html"
+store-position: ("#rustdoc-modnav > h2", {"x": h2_x, "y": h2_y})
+store-position: ("#rustdoc-modnav > ul:first-of-type > li:first-of-type", {"x": x, "y": y})
+call-function: ("check-positions", {"url": "/test_docs/fields/struct.Struct.html"})
+call-function: ("check-positions", {"url": "/test_docs/fields/union.Union.html"})
+call-function: ("check-positions", {"url": "/test_docs/fields/enum.Enum.html"})