1 files changed, 301 insertions, 0 deletions

diff --git a/crates/ide_diagnostics/src/handlers/unlinked_file.rs b/crates/ide_diagnostics/src/handlers/unlinked_file.rs
new file mode 100644
index 000000000..8921ddde2
--- /dev/null
+++ b/crates/ide_diagnostics/src/handlers/unlinked_file.rs
@@ -0,0 +1,301 @@
+//! Diagnostic emitted for files that aren't part of any crate.
+
+use hir::db::DefDatabase;
+use ide_db::{
+    base_db::{FileId, FileLoader, SourceDatabase, SourceDatabaseExt},
+    source_change::SourceChange,
+    RootDatabase,
+};
+use syntax::{
+    ast::{self, ModuleItemOwner, NameOwner},
+    AstNode, TextRange, TextSize,
+};
+use text_edit::TextEdit;
+
+use crate::{fix, Assist, Diagnostic, DiagnosticsContext};
+
+#[derive(Debug)]
+pub(crate) struct UnlinkedFile {
+    pub(crate) file: FileId,
+}
+
+// Diagnostic: unlinked-file
+//
+// This diagnostic is shown for files that are not included in any crate, or files that are part of
+// crates rust-analyzer failed to discover. The file will not have IDE features available.
+pub(crate) fn unlinked_file(ctx: &DiagnosticsContext, d: &UnlinkedFile) -> Diagnostic {
+    // Limit diagnostic to the first few characters in the file. This matches how VS Code
+    // renders it with the full span, but on other editors, and is less invasive.
+    let range = ctx.sema.db.parse(d.file).syntax_node().text_range();
+    // FIXME: This is wrong if one of the first three characters is not ascii: `//Ы`.
+    let range = range.intersect(TextRange::up_to(TextSize::of("..."))).unwrap_or(range);
+
+    Diagnostic::new("unlinked-file", "file not included in module tree", range)
+        .with_fixes(fixes(ctx, d))
+}
+
+fn fixes(ctx: &DiagnosticsContext, d: &UnlinkedFile) -> Option<Vec<Assist>> {
+    // If there's an existing module that could add `mod` or `pub mod` items to include the unlinked file,
+    // suggest that as a fix.
+
+    let source_root = ctx.sema.db.source_root(ctx.sema.db.file_source_root(d.file));
+    let our_path = source_root.path_for_file(&d.file)?;
+    let module_name = our_path.name_and_extension()?.0;
+
+    // Candidates to look for:
+    // - `mod.rs` in the same folder
+    //   - we also check `main.rs` and `lib.rs`
+    // - `$dir.rs` in the parent folder, where `$dir` is the directory containing `self.file_id`
+    let parent = our_path.parent()?;
+    let mut paths = vec![parent.join("mod.rs")?, parent.join("lib.rs")?, parent.join("main.rs")?];
+
+    // `submod/bla.rs` -> `submod.rs`
+    if let Some(newmod) = (|| {
+        let name = parent.name_and_extension()?.0;
+        parent.parent()?.join(&format!("{}.rs", name))
+    })() {
+        paths.push(newmod);
+    }
+
+    for path in &paths {
+        if let Some(parent_id) = 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;
+                    }
+
+                    if module.origin.file_id() == Some(*parent_id) {
+                        return make_fixes(ctx.sema.db, *parent_id, module_name, d.file);
+                    }
+                }
+            }
+        }
+    }
+
+    None
+}
+
+fn make_fixes(
+    db: &RootDatabase,
+    parent_file_id: FileId,
+    new_mod_name: &str,
+    added_file_id: FileId,
+) -> Option<Vec<Assist>> {
+    fn is_outline_mod(item: &ast::Item) -> bool {
+        matches!(item, ast::Item::Module(m) if m.item_list().is_none())
+    }
+
+    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();
+
+    // 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() {
+        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 {
+                    cov_mark::hit!(unlinked_file_skip_fix_when_mod_already_exists);
+                    return None;
+                }
+            }
+        }
+    }
+
+    // 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(|item| is_outline_mod(item))
+        .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));
+        }
+        None => {
+            // Prepend before the first item in the file.
+            match ast.items().next() {
+                Some(item) => {
+                    cov_mark::hit!(unlinked_file_prepend_before_first_item);
+                    let offset = item.syntax().text_range().start();
+                    mod_decl_builder.insert(offset, format!("{}\n\n", mod_decl));
+                    pub_mod_decl_builder.insert(offset, format!("{}\n\n", pub_mod_decl));
+                }
+                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!("{}\n", mod_decl));
+                    pub_mod_decl_builder.insert(offset, format!("{}\n", pub_mod_decl));
+                }
+            }
+        }
+    }
+
+    let trigger_range = db.parse(added_file_id).tree().syntax().text_range();
+    Some(vec![
+        fix(
+            "add_mod_declaration",
+            &format!("Insert `{}`", mod_decl),
+            SourceChange::from_text_edit(parent_file_id, mod_decl_builder.finish()),
+            trigger_range,
+        ),
+        fix(
+            "add_pub_mod_declaration",
+            &format!("Insert `{}`", pub_mod_decl),
+            SourceChange::from_text_edit(parent_file_id, pub_mod_decl_builder.finish()),
+            trigger_range,
+        ),
+    ])
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_diagnostics, check_fix, check_fixes, check_no_fix};
+
+    #[test]
+    fn unlinked_file_prepend_first_item() {
+        cov_mark::check!(unlinked_file_prepend_before_first_item);
+        // Only tests the first one for `pub mod` since the rest are the same
+        check_fixes(
+            r#"
+//- /main.rs
+fn f() {}
+//- /foo.rs
+$0
+"#,
+            vec![
+                r#"
+mod foo;
+
+fn f() {}
+"#,
+                r#"
+pub mod foo;
+
+fn f() {}
+"#,
+            ],
+        );
+    }
+
+    #[test]
+    fn unlinked_file_append_mod() {
+        cov_mark::check!(unlinked_file_append_to_existing_mods);
+        check_fix(
+            r#"
+//- /main.rs
+//! Comment on top
+
+mod preexisting;
+
+mod preexisting2;
+
+struct S;
+
+mod preexisting_bottom;)
+//- /foo.rs
+$0
+"#,
+            r#"
+//! Comment on top
+
+mod preexisting;
+
+mod preexisting2;
+mod foo;
+
+struct S;
+
+mod preexisting_bottom;)
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_insert_in_empty_file() {
+        cov_mark::check!(unlinked_file_empty_file);
+        check_fix(
+            r#"
+//- /main.rs
+//- /foo.rs
+$0
+"#,
+            r#"
+mod foo;
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_old_style_modrs() {
+        check_fix(
+            r#"
+//- /main.rs
+mod submod;
+//- /submod/mod.rs
+// in mod.rs
+//- /submod/foo.rs
+$0
+"#,
+            r#"
+// in mod.rs
+mod foo;
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_new_style_mod() {
+        check_fix(
+            r#"
+//- /main.rs
+mod submod;
+//- /submod.rs
+//- /submod/foo.rs
+$0
+"#,
+            r#"
+mod foo;
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_with_cfg_off() {
+        cov_mark::check!(unlinked_file_skip_fix_when_mod_already_exists);
+        check_no_fix(
+            r#"
+//- /main.rs
+#[cfg(never)]
+mod foo;
+
+//- /foo.rs
+$0
+"#,
+        );
+    }
+
+    #[test]
+    fn unlinked_file_with_cfg_on() {
+        check_diagnostics(
+            r#"
+//- /main.rs
+#[cfg(not(never))]
+mod foo;
+
+//- /foo.rs
+"#,
+        );
+    }
+}