Add ide-assist: generate_documentation_from_trait

crates/ide-assists/src/handlers/generate_documentation_from_trait.rs

@@ -0,0 +1,190 @@
+use hir::{AsAssocItem, HasSource};
+use ide_db::assists::AssistId;
+use syntax::{
+    AstNode, NodeOrToken, SyntaxElement,
+    ast::{
+        self, AnyHasName, HasDocComments, HasName,
+        edit::{AstNodeEdit, IndentLevel},
+        make,
+    },
+    syntax_editor::Position,
+};
+
+use crate::assist_context::{AssistContext, Assists};
+
+// Assist: generate_documentation_from_trait
+//
+// Generate documents from items defined in the trait.
+//
+// ```
+// trait Foo {
+//     /// some docs
+//     fn foo(&self);
+// }
+// impl Foo for () {
+//     fn $0foo(&self) {}
+// }
+// ```
+// ->
+// ```
+// trait Foo {
+//     /// some docs
+//     fn foo(&self);
+// }
+// impl Foo for () {
+//     /// some docs
+//     fn foo(&self) {}
+// }
+// ```
+pub(crate) fn generate_documentation_from_trait(
+    acc: &mut Assists,
+    ctx: &AssistContext<'_>,
+) -> Option<()> {
+    let name = ctx.find_node_at_offset::<ast::Name>()?;
+    let ast_func = name.syntax().parent().and_then(ast::Fn::cast)?;
+    if ast_func.doc_comments().next().is_some() {
+        return None;
+    }
+    let assoc_item = ctx.sema.to_def(&ast_func)?.as_assoc_item(ctx.db())?;
+    let trait_ = assoc_item.implemented_trait(ctx.db())?.source(ctx.db())?.value;
+    let origin_item = trait_.assoc_item_list()?.assoc_items().find(|it| {
+        AnyHasName::cast(it.syntax().clone())
+            .and_then(|it| it.name())
+            .is_some_and(|it| it.text() == name.text())
+    })?;
+    let _first = origin_item.doc_comments().next()?;
+
+    let comments = origin_item.doc_comments();
+    let indent = ast_func.indent_level();
+    let origin_indent = origin_item.indent_level();
+
+    acc.add(
+        AssistId::generate("generate_documentation_from_trait"),
+        "Generate a documentation from trait",
+        ast_func.syntax().text_range(),
+        |builder| {
+            let mut edit = builder.make_editor(ast_func.syntax());
+
+            let comments = comments
+                .flat_map(|doc| {
+                    generate_docs(doc.doc_comment().unwrap_or(""), indent, origin_indent)
+                })
+                .collect();
+            edit.insert_all(Position::before(ast_func.syntax()), comments);
+
+            builder.add_file_edits(ctx.vfs_file_id(), edit);
+        },
+    )
+}
+
+fn generate_docs(doc: &str, indent: IndentLevel, origin_indent: IndentLevel) -> Vec<SyntaxElement> {
+    let ws = format!("\n{indent}");
+    let trim_indent = origin_indent.to_string();
+
+    doc.trim_end()
+        .split('\n')
+        .flat_map(|doc| {
+            let trimmed_doc = line_doc(&trim_indent, doc);
+            [make::tokens::doc_comment(&trimmed_doc), make::tokens::whitespace(&ws)]
+        })
+        .map(NodeOrToken::Token)
+        .collect()
+}
+
+fn line_doc(trim_indent: &str, line: &str) -> String {
+    let text = line.strip_prefix(trim_indent).unwrap_or(line.trim()).trim_end();
+    if text.is_empty() { "///".to_owned() } else { format!("/// {text}") }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_generate_documentation_from_trait() {
+        check_assist(
+            generate_documentation_from_trait,
+            r#"
+trait Foo {
+    /// some docs
+    ///
+    /// # Examples
+    /// ...
+    fn foo(&self);
+}
+impl Foo for () {
+    fn $0foo(&self) {}
+}
+            "#,
+            r#"
+trait Foo {
+    /// some docs
+    ///
+    /// # Examples
+    /// ...
+    fn foo(&self);
+}
+impl Foo for () {
+    /// some docs
+    ///
+    /// # Examples
+    /// ...
+    fn foo(&self) {}
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_generate_documentation_from_trait_with_multi_line() {
+        check_assist(
+            generate_documentation_from_trait,
+            r#"
+trait Foo {
+    /** some docs
+    ...
+    */
+    fn foo(&self);
+}
+impl Foo for () {
+    fn $0foo(&self) {}
+}
+            "#,
+            r#"
+trait Foo {
+    /** some docs
+    ...
+    */
+    fn foo(&self);
+}
+impl Foo for () {
+    /// some docs
+    /// ...
+    fn foo(&self) {}
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_generate_documentation_from_trait_not_applicable_existing_doc() {
+        check_assist_not_applicable(
+            generate_documentation_from_trait,
+            r#"
+trait Foo {
+    /// some docs
+    ///
+    /// # Examples
+    /// ...
+    fn foo(&self);
+}
+impl Foo for () {
+    /// existing docs
+    fn $0foo(&self) {}
+}
+            "#,
+        );
+    }
+}

crates/ide-assists/src/lib.rs

@@ -160,6 +160,7 @@ mod handlers {
     mod generate_delegate_trait;
     mod generate_deref;
     mod generate_derive;
+    mod generate_documentation_from_trait;
     mod generate_documentation_template;
     mod generate_enum_is_method;
     mod generate_enum_projection_method;
@@ -293,6 +294,7 @@ mod handlers {
             generate_derive::generate_derive,
             generate_documentation_template::generate_doc_example,
             generate_documentation_template::generate_documentation_template,
+            generate_documentation_from_trait::generate_documentation_from_trait,
             generate_enum_is_method::generate_enum_is_method,
             generate_enum_projection_method::generate_enum_as_method,
             generate_enum_projection_method::generate_enum_try_into_method,

crates/ide-assists/src/tests/generated.rs

@@ -1563,6 +1563,32 @@ pub fn add(a: i32, b: i32) -> i32 { a + b }
     )
 }
 
+#[test]
+fn doctest_generate_documentation_from_trait() {
+    check_doc_test(
+        "generate_documentation_from_trait",
+        r#####"
+trait Foo {
+    /// some docs
+    fn foo(&self);
+}
+impl Foo for () {
+    fn $0foo(&self) {}
+}
+"#####,
+        r#####"
+trait Foo {
+    /// some docs
+    fn foo(&self);
+}
+impl Foo for () {
+    /// some docs
+    fn foo(&self) {}
+}
+"#####,
+    )
+}
+
 #[test]
 fn doctest_generate_documentation_template() {
     check_doc_test(

crates/syntax/src/ast/make.rs

@@ -1399,7 +1399,7 @@ pub mod tokens {
     pub fn doc_comment(text: &str) -> SyntaxToken {
         assert!(!text.trim().is_empty());
         let sf = SourceFile::parse(text, Edition::CURRENT).ok().unwrap();
-        sf.syntax().first_child_or_token().unwrap().into_token().unwrap()
+        sf.syntax().clone_for_update().first_child_or_token().unwrap().into_token().unwrap()
     }
 
     pub fn literal(text: &str) -> SyntaxToken {