rustfmt doc code blocks with multiple comma-separated attributes

Added test covering this. Chose to treat the code block
as rust if and only if all of the comma-separated attributes
are rust-valid. Chose to allow/preserve whitespace around commas

Fixes rust-lang#3158

Author: nipunn1313

src/comment.rs

@@ -394,28 +394,26 @@ fn identify_comment(
     }
 }
 
-/// Attributes for code blocks in rustdoc.
-/// See https://doc.rust-lang.org/rustdoc/print.html#attributes
+/// Enum indicating if the code block contains rust based on attributes
 enum CodeBlockAttribute {
     Rust,
-    Ignore,
-    Text,
-    ShouldPanic,
-    NoRun,
-    CompileFail,
+    NotRust,
 }
 
 impl CodeBlockAttribute {
-    fn new(attribute: &str) -> CodeBlockAttribute {
-        match attribute {
-            "rust" | "" => CodeBlockAttribute::Rust,
-            "ignore" => CodeBlockAttribute::Ignore,
-            "text" => CodeBlockAttribute::Text,
-            "should_panic" => CodeBlockAttribute::ShouldPanic,
-            "no_run" => CodeBlockAttribute::NoRun,
-            "compile_fail" => CodeBlockAttribute::CompileFail,
-            _ => CodeBlockAttribute::Text,
+    /// Parse comma separated attributes list. Return rust only if all
+    /// attributes are valid rust attributes
+    /// See https://doc.rust-lang.org/rustdoc/print.html#attributes
+    fn new(attributes: &str) -> CodeBlockAttribute {
+        for attribute in attributes.split(",") {
+            match attribute.trim() {
+                "" | "rust" | "should_panic" | "no_run" | "edition2015" | "edition2018"
+                | "edition2021" => (),
+                "ignore" | "compile_fail" | "text" => return CodeBlockAttribute::NotRust,
+                _ => return CodeBlockAttribute::NotRust,
+            }
         }
+        CodeBlockAttribute::Rust
     }
 }
 
@@ -649,25 +647,21 @@ impl<'a> CommentRewrite<'a> {
         } else if self.code_block_attr.is_some() {
             if line.starts_with("```") {
                 let code_block = match self.code_block_attr.as_ref().unwrap() {
-                    CodeBlockAttribute::Ignore | CodeBlockAttribute::Text => {
-                        trim_custom_comment_prefix(&self.code_block_buffer)
-                    }
-                    _ if self.code_block_buffer.is_empty() => String::new(),
-                    _ => {
+                    CodeBlockAttribute::Rust
+                        if self.fmt.config.format_code_in_doc_comments()
+                            && !self.code_block_buffer.is_empty() =>
+                    {
                         let mut config = self.fmt.config.clone();
                         config.set().wrap_comments(false);
-                        if config.format_code_in_doc_comments() {
-                            if let Some(s) =
-                                crate::format_code_block(&self.code_block_buffer, &config, false)
-                            {
-                                trim_custom_comment_prefix(&s.snippet)
-                            } else {
-                                trim_custom_comment_prefix(&self.code_block_buffer)
-                            }
+                        if let Some(s) =
+                            crate::format_code_block(&self.code_block_buffer, &config, false)
+                        {
+                            trim_custom_comment_prefix(&s.snippet)
                         } else {
                             trim_custom_comment_prefix(&self.code_block_buffer)
                         }
                     }
+                    _ => trim_custom_comment_prefix(&self.code_block_buffer),
                 };
                 if !code_block.is_empty() {
                     self.result.push_str(&self.comment_line_separator);

tests/source/issue-3158.rs

@@ -0,0 +1,74 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// Should format
+/// ```rust
+/// assert!( false );
+/// ```
+///
+/// Should format
+/// ```rust,should_panic
+/// assert!( false );
+/// ```
+///
+/// Should format
+/// ```rust,should_panic,edition2018
+/// assert!( false );
+/// ```
+///
+/// Should format
+/// ```rust , should_panic , edition2018
+/// assert!( false );
+/// ```
+///
+/// Should not format
+/// ```ignore
+/// assert!( false );
+/// ```
+///
+/// Should not format (not all are rust)
+/// ```rust,ignore
+/// assert!( false );
+/// ```
+///
+/// Should not format (rust compile_fail)
+/// ```compile_fail
+/// assert!( false );
+/// ```
+///
+/// Should not format (rust compile_fail)
+/// ```rust,compile_fail
+/// assert!( false );
+/// ```
+///
+/// Various unspecified ones that should format
+/// ```
+/// assert!( false );
+/// ```
+///
+/// ```,
+/// assert!( false );
+/// ```
+///
+/// ```,,,,,
+/// assert!( false );
+/// ```
+///
+/// ```,,,  rust  ,,
+/// assert!( false );
+/// ```
+///
+/// Should not format
+/// ```,,,  rust  ,  ignore,
+/// assert!( false );
+/// ```
+///
+/// Few empty ones
+/// ```
+/// ```
+///
+/// ```rust
+/// ```
+///
+/// ```ignore
+/// ```
+fn foo() {}

tests/target/issue-3158.rs

@@ -0,0 +1,74 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// Should format
+/// ```rust
+/// assert!(false);
+/// ```
+///
+/// Should format
+/// ```rust,should_panic
+/// assert!(false);
+/// ```
+///
+/// Should format
+/// ```rust,should_panic,edition2018
+/// assert!(false);
+/// ```
+///
+/// Should format
+/// ```rust , should_panic , edition2018
+/// assert!(false);
+/// ```
+///
+/// Should not format
+/// ```ignore
+/// assert!( false );
+/// ```
+///
+/// Should not format (not all are rust)
+/// ```rust,ignore
+/// assert!( false );
+/// ```
+///
+/// Should not format (rust compile_fail)
+/// ```compile_fail
+/// assert!( false );
+/// ```
+///
+/// Should not format (rust compile_fail)
+/// ```rust,compile_fail
+/// assert!( false );
+/// ```
+///
+/// Various unspecified ones that should format
+/// ```
+/// assert!(false);
+/// ```
+///
+/// ```,
+/// assert!(false);
+/// ```
+///
+/// ```,,,,,
+/// assert!(false);
+/// ```
+///
+/// ```,,,  rust  ,,
+/// assert!(false);
+/// ```
+///
+/// Should not format
+/// ```,,,  rust  ,  ignore,
+/// assert!( false );
+/// ```
+///
+/// Few empty ones
+/// ```
+/// ```
+///
+/// ```rust
+/// ```
+///
+/// ```ignore
+/// ```
+fn foo() {}