Merge #11869

11869: fix: code blocks with tilde also works like code block r=Veykril a=moreal

The `rustdoc` uses the `pulldown_cmark` package to parse *doc_comment* and the package also treat triple `~` characters also as code block fences. So when we run `cargo doc`, they will be placed also.

<img width="965" alt="image" src="https://user-images.githubusercontent.com/26626194/161208072-5a09a209-57fc-4a52-b190-b0a9be9ffcd6.png">

But `rust-analyzer` doesn't support it so it doesn't have any injected code highlights and any `Run doctest` hint. This pull request tries to allow also them. 🙇🏻‍♂️ 

Before:

<img width="224" alt="image" src="https://user-images.githubusercontent.com/26626194/161207405-b1d6cfda-82b1-4f60-8e42-c51d0ed98f38.png">

After:

<img width="161" alt="image" src="https://user-images.githubusercontent.com/26626194/161207693-8e39997c-9ca6-4e69-8c65-e9b70899f7db.png">


Co-authored-by: Lee Dogeon <dev.moreal@gmail.com>

crates/ide/src/runnables.rs

@@ -474,7 +474,7 @@ impl TestAttr {
     }
 }
 
-const RUSTDOC_FENCE: &str = "```";
+const RUSTDOC_FENCES: [&str; 2] = ["```", "~~~"];
 const RUSTDOC_CODE_BLOCK_ATTRIBUTES_RUNNABLE: &[&str] =
     &["", "rust", "should_panic", "edition2015", "edition2018", "edition2021"];
 
@@ -483,7 +483,9 @@ fn has_runnable_doc_test(attrs: &hir::Attrs) -> bool {
         let mut in_code_block = false;
 
         for line in String::from(doc).lines() {
-            if let Some(header) = line.strip_prefix(RUSTDOC_FENCE) {
+            if let Some(header) =
+                RUSTDOC_FENCES.into_iter().find_map(|fence| line.strip_prefix(fence))
+            {
                 in_code_block = !in_code_block;
 
                 if in_code_block

crates/ide/src/syntax_highlighting/inject.rs

@@ -78,7 +78,8 @@ pub(super) fn ra_fixture(
     Some(())
 }
 
-const RUSTDOC_FENCE: &str = "```";
+const RUSTDOC_FENCE_LENGTH: usize = 3;
+const RUSTDOC_FENCES: [&str; 2] = ["```", "~~~"];
 
 /// Injection of syntax highlighting of doctests.
 pub(super) fn doc_comment(
@@ -166,11 +167,11 @@ pub(super) fn doc_comment(
             };
             let mut pos = TextSize::from(0);
 
-            match line.find(RUSTDOC_FENCE) {
+            match RUSTDOC_FENCES.into_iter().find_map(|fence| line.find(fence)) {
                 Some(idx) => {
                     is_codeblock = !is_codeblock;
                     // Check whether code is rust by inspecting fence guards
-                    let guards = &line[idx + RUSTDOC_FENCE.len()..];
+                    let guards = &line[idx + RUSTDOC_FENCE_LENGTH..];
                     let is_rust = is_rust_fence(guards);
                     is_doctest = is_codeblock && is_rust;
                     continue;

crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html

@@ -110,6 +110,11 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="comment documentation">///</span><span class="comment documentation"> </span><span class="keyword injected">let</span><span class="none injected"> </span><span class="variable declaration injected">foobar</span><span class="none injected"> </span><span class="operator injected">=</span><span class="none injected"> </span><span class="struct injected">Foo</span><span class="operator injected">::</span><span class="function injected">new</span><span class="parenthesis injected">(</span><span class="parenthesis injected">)</span><span class="operator injected">.</span><span class="function injected">bar</span><span class="parenthesis injected">(</span><span class="parenthesis injected">)</span><span class="semicolon injected">;</span>
     <span class="comment documentation">/// ```</span>
     <span class="comment documentation">///</span>
+    <span class="comment documentation">/// ~~~rust,no_run</span>
+    <span class="comment documentation">///</span><span class="comment documentation"> </span><span class="comment injected">// code block with tilde.</span>
+    <span class="comment documentation">///</span><span class="comment documentation"> </span><span class="keyword injected">let</span><span class="none injected"> </span><span class="variable declaration injected">foobar</span><span class="none injected"> </span><span class="operator injected">=</span><span class="none injected"> </span><span class="struct injected">Foo</span><span class="operator injected">::</span><span class="function injected">new</span><span class="parenthesis injected">(</span><span class="parenthesis injected">)</span><span class="operator injected">.</span><span class="function injected">bar</span><span class="parenthesis injected">(</span><span class="parenthesis injected">)</span><span class="semicolon injected">;</span>
+    <span class="comment documentation">/// ~~~</span>
+    <span class="comment documentation">///</span>
     <span class="comment documentation">/// ```</span>
     <span class="comment documentation">///</span><span class="comment documentation"> </span><span class="comment injected">// functions</span>
     <span class="comment documentation">///</span><span class="comment documentation"> </span><span class="keyword injected">fn</span><span class="none injected"> </span><span class="function declaration injected">foo</span><span class="angle injected">&lt;</span><span class="type_param declaration injected">T</span><span class="comma injected">,</span><span class="none injected"> </span><span class="keyword injected">const</span><span class="none injected"> </span><span class="const_param declaration injected">X</span><span class="colon injected">:</span><span class="none injected"> </span><span class="builtin_type injected">usize</span><span class="angle injected">&gt;</span><span class="parenthesis injected">(</span><span class="value_param declaration injected">arg</span><span class="colon injected">:</span><span class="none injected"> </span><span class="builtin_type injected">i32</span><span class="parenthesis injected">)</span><span class="none injected"> </span><span class="brace injected">{</span>

crates/ide/src/syntax_highlighting/tests.rs

@@ -644,6 +644,11 @@ impl Foo {
     /// let foobar = Foo::new().bar();
     /// ```
     ///
+    /// ~~~rust,no_run
+    /// // code block with tilde.
+    /// let foobar = Foo::new().bar();
+    /// ~~~
+    ///
     /// ```
     /// // functions
     /// fn foo<T, const X: usize>(arg: i32) {

crates/rust-analyzer/src/markdown.rs

@@ -1,7 +1,7 @@
 //! Transforms markdown
 use ide_db::rust_doc::is_rust_fence;
 
-const RUSTDOC_FENCE: &str = "```";
+const RUSTDOC_FENCES: [&str; 2] = ["```", "~~~"];
 
 pub(crate) fn format_docs(src: &str) -> String {
     let mut processed_lines = Vec::new();
@@ -13,7 +13,8 @@ pub(crate) fn format_docs(src: &str) -> String {
             continue;
         }
 
-        if let Some(header) = line.strip_prefix(RUSTDOC_FENCE) {
+        if let Some(header) = RUSTDOC_FENCES.into_iter().find_map(|fence| line.strip_prefix(fence))
+        {
             in_code_block ^= true;
 
             if in_code_block {