rustdoc: force pre tags to have the default line height

Fixes #105906

Author: notriddle

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

@@ -342,6 +342,7 @@ code, pre, a.test-arrow, .code-header {
 }
 pre {
 	padding: 14px;
+	line-height: 1.5; /* https://github.com/rust-lang/rust/issues/105906 */
 }
 .item-decl pre {
 	overflow-x: auto;

src/test/rustdoc-gui/codeblock-sub.goml

@@ -0,0 +1,5 @@
+// Test that code blocks nested within <sub> do not have a line height of 0.
+goto: "file://" + |DOC_PATH| + "/test_docs/codeblock_sub/index.html"
+
+store-property: (codeblock_sub_1, "#codeblock-sub-1", "offsetHeight")
+assert-property-false: ("#codeblock-sub-3", { "offsetHeight": |codeblock_sub_1| })

src/test/rustdoc-gui/src/test_docs/lib.rs

@@ -455,3 +455,22 @@ impl TypeWithImplDoc {
     /// fn doc
     pub fn test_fn() {}
 }
+
+/// <sub id="codeblock-sub-1">
+///
+/// ```
+/// one
+/// ```
+///
+/// </sub>
+///
+/// <sub id="codeblock-sub-3">
+///
+/// ```
+/// one
+/// two
+/// three
+/// ```
+///
+/// </sub>
+pub mod codeblock_sub {}