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Trim trailing whitespace in Rust code blocks
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Before, a code block would always end with a final newline. This was
added by the `hide_lines` function unconditionally.

When the code block is syntax highlighted by highlight.js, this is not
a problem, no empty line is added for a final trailing `\n` character.
However, when the code block is editable and thus handled by the ACE
editor, a trailing newline _is_ significant. I believe this issue is
most closely described by ajaxorg/ace#2083.

The effect of the way ACE handles newlines is that a code block like

    <pre>
      Some code
    </pre>

will create an editor with _two_ lines, not just one.

By trimming trailing whitespace, we ensure that we don’t accidentally
create more lines in the ACE editor than necessary.
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@mgeisler
mgeisler committed Jun 29, 2022
1 parent 0547868 commit d5dc5f6
Showing 1 changed file with 39 additions and 25 deletions.
64 changes: 39 additions & 25 deletions src/renderer/html_handlebars/hbs_renderer.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -906,28 +906,42 @@ fn hide_lines(content: &str) -> String {
}

let mut result = String::with_capacity(content.len());
for line in content.lines() {
let mut lines = content.lines();
let last_line = lines.next_back();
let mut handle_line = |line: &str, newline: &str| {
if let Some(caps) = BORING_LINES_REGEX.captures(line) {
if &caps[2] == "#" {
result += &caps[1];
result += &caps[2];
result += &caps[3];
result += "\n";
continue;
} else if &caps[2] != "!" && &caps[2] != "[" {
return;
}

if &caps[2] != "!" && &caps[2] != "[" {
result += "<span class=\"boring\">";
result += &caps[1];
if &caps[2] != " " {
result += &caps[2];
}
result += &caps[3];
result += "\n";
result += newline;
result += "</span>";
continue;
return;
}
}

result += line;
result += "\n";
result += newline;
};

// Iterate over all lines except the last:
for line in lines {
handle_line(line, "\n");
}
// Handle the last line, if any:
if let Some(line) = last_line {
handle_line(line, "");
}
result
}
Expand Down Expand Up @@ -1007,19 +1021,19 @@ mod tests {
fn add_playground() {
let inputs = [
("<code class=\"language-rust\">x()</code>",
"<pre class=\"playground\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
("<code class=\"language-rust\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>"),
("<code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code>",
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code></pre>"),
("<code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code>",
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>"),
("<code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code>",
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";</code></pre>"),
("<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>",
"<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";\n</code>"),
"<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code>"),
("<code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code>",
"<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>"),
];
for (src, should_be) in &inputs {
let got = add_playground_pre(
Expand All @@ -1037,13 +1051,13 @@ mod tests {
fn add_playground_edition2015() {
let inputs = [
("<code class=\"language-rust\">x()</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2015\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2015\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
("<code class=\"language-rust\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2015\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2018\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
];
for (src, should_be) in &inputs {
let got = add_playground_pre(
Expand All @@ -1061,13 +1075,13 @@ mod tests {
fn add_playground_edition2018() {
let inputs = [
("<code class=\"language-rust\">x()</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2018\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2018\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
("<code class=\"language-rust\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2015\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2018\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
];
for (src, should_be) in &inputs {
let got = add_playground_pre(
Expand All @@ -1085,13 +1099,13 @@ mod tests {
fn add_playground_edition2021() {
let inputs = [
("<code class=\"language-rust\">x()</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2021\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2021\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
("<code class=\"language-rust\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2015\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
("<code class=\"language-rust edition2018\">fn main() {}</code>",
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
"<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
];
for (src, should_be) in &inputs {
let got = add_playground_pre(
Expand Down

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