Auto merge of #137229 - GuillaumeGomez:expand-macro, r=lolbinarycat

Add support for macro expansion in rustdoc source code pages

This is what it looks like:

![Screenshot From 2025-02-18 18-08-51](https://github.com/user-attachments/assets/ce2b3806-6218-47df-94bf-e9e9ed40cd41)

![image](https://github.com/user-attachments/assets/891042db-8632-4dba-9343-e28570c058fe)

You can test it [here](https://rustdoc.crud.net/imperio/macro-expansion/src/lib/lib.rs.html). In this case, I also enabled the `--generate-link-to-definition` to show that both options work well together.

Note: <del>There is a bug currently in firefox where the line numbers are not displayed correctly if they're inside the "macro expansion" span: https://bugzilla.mozilla.org/show_bug.cgi?id=1949948<del> Found a workaround around this bug.

r? `@notriddle`

1 files changed, 48 insertions, 3 deletions

diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index dc27d7943d9..86f1a42bc01 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -956,6 +956,40 @@ rustdoc-topbar {
 .example-wrap.digits-8 { --example-wrap-digits-count: 8ch; }
 .example-wrap.digits-9 { --example-wrap-digits-count: 9ch; }
 
+.example-wrap .expansion {
+	position: relative;
+	display: inline;
+}
+.example-wrap .expansion > input {
+	display: block;
+	position: absolute;
+	appearance: none;
+	content: '↕';
+	left: -20px;
+	top: 0;
+	border: 1px solid var(--border-color);
+	border-radius: 4px;
+	cursor: pointer;
+	color: var(--main-color);
+	padding: 0 2px;
+	line-height: 20px;
+}
+.example-wrap .expansion > input::after {
+	content: "↕";
+}
+.example-wrap .expansion .expanded {
+	display: none;
+	color: var(--main-color);
+}
+.example-wrap .expansion > input:checked ~ .expanded,
+.example-wrap .expansion > input:checked ~ * .expanded {
+	display: inherit;
+}
+.example-wrap .expansion > input:checked ~ .original,
+.example-wrap .expansion > input:checked ~ * .original {
+	display: none;
+}
+
 .example-wrap [data-nosnippet] {
 	width: calc(var(--example-wrap-digits-count) + var(--line-number-padding) * 2);
 }
@@ -964,6 +998,17 @@ rustdoc-topbar {
 		var(--example-wrap-digits-count) + var(--line-number-padding) * 2
 		+ var(--line-number-right-margin));
 }
+.src .example-wrap .expansion [data-nosnippet] {
+	/* FIXME: Once <https://bugzilla.mozilla.org/show_bug.cgi?id=1949948> is solved, uncomment
+	   next line and remove the two other rules. */
+	/*left: calc((
+		var(--example-wrap-digits-count) + var(--line-number-padding) * 2
+		+ var(--line-number-right-margin)) * -1);*/
+	position: initial;
+	margin-left: calc((
+		var(--example-wrap-digits-count) + var(--line-number-padding) * 2
+		+ var(--line-number-right-margin)) * -1);
+}
 
 .example-wrap [data-nosnippet] {
 	color: var(--src-line-numbers-span-color);
@@ -978,9 +1023,6 @@ rustdoc-topbar {
 	position: absolute;
 	left: 0;
 }
-.example-wrap .line-highlighted[data-nosnippet] {
-	background-color: var(--src-line-number-highlighted-background-color);
-}
 .example-wrap pre > code {
 	position: relative;
 	display: block;
@@ -995,6 +1037,9 @@ rustdoc-topbar {
 .example-wrap [data-nosnippet]:target {
 	border-right: none;
 }
+.example-wrap .line-highlighted[data-nosnippet] {
+	background-color: var(--src-line-number-highlighted-background-color);
+}
 .example-wrap.hide-lines [data-nosnippet] {
 	display: none;
 }