Auto merge of #13934 - Veykril:unlinked-file-inline-modules, r=Veykril

feat: Make unlinked_file diagnostic quickfixes work for inline modules

Finally got myself to fix this, bothered me quite a bit that this never worked
![Code_Qe3WlMvt5Q](https://user-images.githubusercontent.com/3757771/211927799-023e48ee-7cdd-4dd7-8e25-a23eddc7d897.gif)

(Just gotta fix up the indentation still)

4 files changed, 204 insertions, 52 deletions

diff --git a/crates/hir-expand/src/lib.rs b/crates/hir-expand/src/lib.rs
index 5554c7517f5..b879eec4cc8 100644
--- a/crates/hir-expand/src/lib.rs
+++ b/crates/hir-expand/src/lib.rs
@@ -356,6 +356,14 @@ impl HirFileId {
         }
     }
 
+    #[inline]
+    pub fn file_id(self) -> Option<FileId> {
+        match self.0 & Self::MACRO_FILE_TAG_MASK {
+            0 => Some(FileId(self.0)),
+            _ => None,
+        }
+    }
+
     fn repr(self) -> HirFileIdRepr {
         match self.0 & Self::MACRO_FILE_TAG_MASK {
             0 => HirFileIdRepr::FileId(FileId(self.0)),
diff --git a/crates/ide-diagnostics/src/handlers/unlinked_file.rs b/crates/ide-diagnostics/src/handlers/unlinked_file.rs
index be70f0ac4f7..3d45a75913a 100644
--- a/crates/ide-diagnostics/src/handlers/unlinked_file.rs
+++ b/crates/ide-diagnostics/src/handlers/unlinked_file.rs
@@ -1,13 +1,15 @@
 //! Diagnostic emitted for files that aren't part of any crate.
 
-use hir::db::DefDatabase;
+use std::iter;
+
+use hir::{db::DefDatabase, InFile, ModuleSource};
 use ide_db::{
     base_db::{FileId, FileLoader, SourceDatabase, SourceDatabaseExt},
     source_change::SourceChange,
     RootDatabase,
 };
 use syntax::{
-    ast::{self, HasModuleItem, HasName},
+    ast::{self, edit::IndentLevel, HasModuleItem, HasName},
     AstNode, TextRange, TextSize,
 };
 use text_edit::TextEdit;
@@ -42,47 +44,99 @@ fn fixes(ctx: &DiagnosticsContext<'_>, file_id: FileId) -> Option<Vec<Assist>> {
 
     let source_root = ctx.sema.db.source_root(ctx.sema.db.file_source_root(file_id));
     let our_path = source_root.path_for_file(&file_id)?;
-    let (mut module_name, _) = our_path.name_and_extension()?;
-
-    // Candidates to look for:
-    // - `mod.rs`, `main.rs` and `lib.rs` in the same folder
-    // - `$dir.rs` in the parent folder, where `$dir` is the directory containing `self.file_id`
     let parent = our_path.parent()?;
-    let paths = {
-        let parent = if module_name == "mod" {
-            // for mod.rs we need to actually look up one higher
-            // and take the parent as our to be module name
-            let (name, _) = parent.name_and_extension()?;
-            module_name = name;
-            parent.parent()?
-        } else {
-            parent
-        };
-        let mut paths =
-            vec![parent.join("mod.rs")?, parent.join("lib.rs")?, parent.join("main.rs")?];
-
-        // `submod/bla.rs` -> `submod.rs`
-        let parent_mod = (|| {
+    let (module_name, _) = our_path.name_and_extension()?;
+    let (parent, module_name) = match module_name {
+        // for mod.rs we need to actually look up one higher
+        // and take the parent as our to be module name
+        "mod" => {
             let (name, _) = parent.name_and_extension()?;
-            parent.parent()?.join(&format!("{name}.rs"))
-        })();
-        paths.extend(parent_mod);
-        paths
+            (parent.parent()?, name.to_owned())
+        }
+        _ => (parent, module_name.to_owned()),
     };
 
-    for &parent_id in paths.iter().filter_map(|path| source_root.file_for_path(path)) {
-        for &krate in ctx.sema.db.relevant_crates(parent_id).iter() {
-            let crate_def_map = ctx.sema.db.crate_def_map(krate);
-            for (_, module) in crate_def_map.modules() {
-                if module.origin.is_inline() {
-                    // We don't handle inline `mod parent {}`s, they use different paths.
-                    continue;
-                }
+    // check crate roots, i.e. main.rs, lib.rs, ...
+    'crates: for &krate in &*ctx.sema.db.relevant_crates(file_id) {
+        let crate_def_map = ctx.sema.db.crate_def_map(krate);
+
+        let root_module = &crate_def_map[crate_def_map.root()];
+        let Some(root_file_id) = root_module.origin.file_id() else { continue };
+        let Some(crate_root_path) = source_root.path_for_file(&root_file_id) else { continue };
+        let Some(rel) = parent.strip_prefix(&crate_root_path.parent()?) else { continue };
+
+        // try resolving the relative difference of the paths as inline modules
+        let mut current = root_module;
+        for ele in rel.as_ref().components() {
+            let seg = match ele {
+                std::path::Component::Normal(seg) => seg.to_str()?,
+                std::path::Component::RootDir => continue,
+                // shouldn't occur
+                _ => continue 'crates,
+            };
+            match current.children.iter().find(|(name, _)| name.to_smol_str() == seg) {
+                Some((_, &child)) => current = &crate_def_map[child],
+                None => continue 'crates,
+            }
+            if !current.origin.is_inline() {
+                continue 'crates;
+            }
+        }
+
+        let InFile { file_id: parent_file_id, value: source } =
+            current.definition_source(ctx.sema.db);
+        let parent_file_id = parent_file_id.file_id()?;
+        return make_fixes(ctx.sema.db, parent_file_id, source, &module_name, file_id);
+    }
 
-                if module.origin.file_id() == Some(parent_id) {
-                    return make_fixes(ctx.sema.db, parent_id, module_name, file_id);
+    // if we aren't adding to a crate root, walk backwards such that we support `#[path = ...]` overrides if possible
+
+    // build all parent paths of the form `../module_name/mod.rs` and `../module_name.rs`
+    let paths = iter::successors(Some(parent.clone()), |prev| prev.parent()).filter_map(|path| {
+        let parent = path.parent()?;
+        let (name, _) = path.name_and_extension()?;
+        Some(([parent.join(&format!("{name}.rs"))?, path.join("mod.rs")?], name.to_owned()))
+    });
+    let mut stack = vec![];
+    let &parent_id =
+        paths.inspect(|(_, name)| stack.push(name.clone())).find_map(|(paths, _)| {
+            paths.into_iter().find_map(|path| source_root.file_for_path(&path))
+        })?;
+    stack.pop();
+    'crates: for &krate in ctx.sema.db.relevant_crates(parent_id).iter() {
+        let crate_def_map = ctx.sema.db.crate_def_map(krate);
+        let Some((_, module)) =
+            crate_def_map.modules()
+            .find(|(_, module)| module.origin.file_id() == Some(parent_id) && !module.origin.is_inline())
+        else { continue };
+
+        if stack.is_empty() {
+            return make_fixes(
+                ctx.sema.db,
+                parent_id,
+                module.definition_source(ctx.sema.db).value,
+                &module_name,
+                file_id,
+            );
+        } else {
+            // direct parent file is missing,
+            // try finding a parent that has an inline tree from here on
+            let mut current = module;
+            for s in stack.iter().rev() {
+                match module.children.iter().find(|(name, _)| name.to_smol_str() == s) {
+                    Some((_, child)) => {
+                        current = &crate_def_map[*child];
+                    }
+                    None => continue 'crates,
+                }
+                if !current.origin.is_inline() {
+                    continue 'crates;
                 }
             }
+            let InFile { file_id: parent_file_id, value: source } =
+                current.definition_source(ctx.sema.db);
+            let parent_file_id = parent_file_id.file_id()?;
+            return make_fixes(ctx.sema.db, parent_file_id, source, &module_name, file_id);
         }
     }
 
@@ -92,6 +146,7 @@ fn fixes(ctx: &DiagnosticsContext<'_>, file_id: FileId) -> Option<Vec<Assist>> {
 fn make_fixes(
     db: &RootDatabase,
     parent_file_id: FileId,
+    source: ModuleSource,
     new_mod_name: &str,
     added_file_id: FileId,
 ) -> Option<Vec<Assist>> {
@@ -102,14 +157,18 @@ fn make_fixes(
     let mod_decl = format!("mod {new_mod_name};");
     let pub_mod_decl = format!("pub mod {new_mod_name};");
 
-    let ast: ast::SourceFile = db.parse(parent_file_id).tree();
-
     let mut mod_decl_builder = TextEdit::builder();
     let mut pub_mod_decl_builder = TextEdit::builder();
 
+    let mut items = match &source {
+        ModuleSource::SourceFile(it) => it.items(),
+        ModuleSource::Module(it) => it.item_list()?.items(),
+        ModuleSource::BlockExpr(_) => return None,
+    };
+
     // If there's an existing `mod m;` statement matching the new one, don't emit a fix (it's
     // probably `#[cfg]`d out).
-    for item in ast.items() {
+    for item in items.clone() {
         if let ast::Item::Module(m) = item {
             if let Some(name) = m.name() {
                 if m.item_list().is_none() && name.to_string() == new_mod_name {
@@ -121,28 +180,40 @@ fn make_fixes(
     }
 
     // If there are existing `mod m;` items, append after them (after the first group of them, rather).
-    match ast.items().skip_while(|item| !is_outline_mod(item)).take_while(is_outline_mod).last() {
+    match items.clone().skip_while(|item| !is_outline_mod(item)).take_while(is_outline_mod).last() {
         Some(last) => {
             cov_mark::hit!(unlinked_file_append_to_existing_mods);
             let offset = last.syntax().text_range().end();
-            mod_decl_builder.insert(offset, format!("\n{mod_decl}"));
-            pub_mod_decl_builder.insert(offset, format!("\n{pub_mod_decl}"));
+            let indent = IndentLevel::from_node(last.syntax());
+            mod_decl_builder.insert(offset, format!("\n{indent}{mod_decl}"));
+            pub_mod_decl_builder.insert(offset, format!("\n{indent}{pub_mod_decl}"));
         }
         None => {
             // Prepend before the first item in the file.
-            match ast.items().next() {
-                Some(item) => {
+            match items.next() {
+                Some(first) => {
                     cov_mark::hit!(unlinked_file_prepend_before_first_item);
-                    let offset = item.syntax().text_range().start();
-                    mod_decl_builder.insert(offset, format!("{mod_decl}\n\n"));
-                    pub_mod_decl_builder.insert(offset, format!("{pub_mod_decl}\n\n"));
+                    let offset = first.syntax().text_range().start();
+                    let indent = IndentLevel::from_node(first.syntax());
+                    mod_decl_builder.insert(offset, format!("{mod_decl}\n\n{indent}"));
+                    pub_mod_decl_builder.insert(offset, format!("{pub_mod_decl}\n\n{indent}"));
                 }
                 None => {
                     // No items in the file, so just append at the end.
                     cov_mark::hit!(unlinked_file_empty_file);
-                    let offset = ast.syntax().text_range().end();
-                    mod_decl_builder.insert(offset, format!("{mod_decl}\n"));
-                    pub_mod_decl_builder.insert(offset, format!("{pub_mod_decl}\n"));
+                    let mut indent = IndentLevel::from(0);
+                    let offset = match &source {
+                        ModuleSource::SourceFile(it) => it.syntax().text_range().end(),
+                        ModuleSource::Module(it) => {
+                            indent = IndentLevel::from_node(it.syntax()) + 1;
+                            it.item_list()?.r_curly_token()?.text_range().start()
+                        }
+                        ModuleSource::BlockExpr(it) => {
+                            it.stmt_list()?.r_curly_token()?.text_range().start()
+                        }
+                    };
+                    mod_decl_builder.insert(offset, format!("{indent}{mod_decl}\n"));
+                    pub_mod_decl_builder.insert(offset, format!("{indent}{pub_mod_decl}\n"));
                 }
             }
         }
@@ -167,7 +238,6 @@ fn make_fixes(
 
 #[cfg(test)]
 mod tests {
-
     use crate::tests::{check_diagnostics, check_fix, check_fixes, check_no_fix};
 
     #[test]
@@ -333,4 +403,62 @@ mod foo;
 "#,
         );
     }
+
+    #[test]
+    fn unlinked_file_insert_into_inline_simple() {
+        check_fix(
+            r#"
+//- /main.rs
+mod bar;
+//- /bar.rs
+mod foo {
+}
+//- /bar/foo/baz.rs
+$0
+"#,
+            r#"
+mod foo {
+    mod baz;
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_insert_into_inline_simple_modrs() {
+        check_fix(
+            r#"
+//- /main.rs
+mod bar;
+//- /bar.rs
+mod baz {
+}
+//- /bar/baz/foo/mod.rs
+$0
+"#,
+            r#"
+mod baz {
+    mod foo;
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_insert_into_inline_simple_modrs_main() {
+        check_fix(
+            r#"
+//- /main.rs
+mod bar {
+}
+//- /bar/foo/mod.rs
+$0
+"#,
+            r#"
+mod bar {
+    mod foo;
+}
+"#,
+        );
+    }
 }
diff --git a/crates/ide/src/goto_declaration.rs b/crates/ide/src/goto_declaration.rs
index c7130a2a4bb..e70bc2ec541 100644
--- a/crates/ide/src/goto_declaration.rs
+++ b/crates/ide/src/goto_declaration.rs
@@ -17,6 +17,7 @@ use crate::{
 // This is the same as `Go to Definition` with the following exceptions:
 // - outline modules will navigate to the `mod name;` item declaration
 // - trait assoc items will navigate to the assoc item of the trait declaration opposed to the trait impl
+// - fields in patterns will navigate to the field declaration of the struct, union or variant
 pub(crate) fn goto_declaration(
     db: &RootDatabase,
     position: FilePosition,
diff --git a/crates/vfs/src/vfs_path.rs b/crates/vfs/src/vfs_path.rs
index b23c9f1966d..38501a8ba5a 100644
--- a/crates/vfs/src/vfs_path.rs
+++ b/crates/vfs/src/vfs_path.rs
@@ -1,7 +1,7 @@
 //! Abstract-ish representation of paths for VFS.
 use std::fmt;
 
-use paths::{AbsPath, AbsPathBuf};
+use paths::{AbsPath, AbsPathBuf, RelPath};
 
 /// Path in [`Vfs`].
 ///
@@ -84,6 +84,14 @@ impl VfsPath {
         }
     }
 
+    pub fn strip_prefix(&self, other: &VfsPath) -> Option<&RelPath> {
+        match (&self.0, &other.0) {
+            (VfsPathRepr::PathBuf(lhs), VfsPathRepr::PathBuf(rhs)) => lhs.strip_prefix(rhs),
+            (VfsPathRepr::VirtualPath(lhs), VfsPathRepr::VirtualPath(rhs)) => lhs.strip_prefix(rhs),
+            (VfsPathRepr::PathBuf(_) | VfsPathRepr::VirtualPath(_), _) => None,
+        }
+    }
+
     /// Returns the `VfsPath` without its final component, if there is one.
     ///
     /// Returns [`None`] if the path is a root or prefix.
@@ -320,6 +328,13 @@ impl VirtualPath {
         self.0.starts_with(&other.0)
     }
 
+    fn strip_prefix(&self, base: &VirtualPath) -> Option<&RelPath> {
+        <_ as AsRef<std::path::Path>>::as_ref(&self.0)
+            .strip_prefix(&base.0)
+            .ok()
+            .map(RelPath::new_unchecked)
+    }
+
     /// Remove the last component of `self`.
     ///
     /// This will find the last `'/'` in `self`, and remove everything after it,