fix: module accessibility

crates/els/definition.rs

@@ -50,7 +50,7 @@ impl<Checker: BuildRunnable> Server<Checker> {
                                 if let Some(path) = self
                                     .get_local_ctx(&uri, pos)
                                     .first()
-                                    .and_then(|ctx| ctx.get_path_from_mod_t(&vi.t))
+                                    .and_then(|ctx| ctx.get_path_with_mod_t(&vi.t))
                                 {
                                     let mod_uri = Url::from_file_path(path).unwrap();
                                     let resp = GotoDefinitionResponse::Array(vec![
@@ -67,7 +67,7 @@ impl<Checker: BuildRunnable> Server<Checker> {
                                 if let Some((_, vi)) = self
                                     .get_local_ctx(&uri, pos)
                                     .first()
-                                    .and_then(|ctx| ctx.get_mod_from_t(mod_t))
+                                    .and_then(|ctx| ctx.get_mod_with_t(mod_t))
                                     .and_then(|mod_ctx| mod_ctx.get_var_info(token.inspect()))
                                 {
                                     let def_uri =

crates/erg_common/pathutil.rs

@@ -1,5 +1,74 @@
+use std::ffi::OsStr;
 use std::path::{Component, Path, PathBuf};
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DirKind {
+    ErgModule,
+    PyModule,
+    Other,
+    NotDir,
+}
+
+impl From<&Path> for DirKind {
+    fn from(path: &Path) -> Self {
+        let Ok(dir) = path.read_dir() else {
+            return DirKind::NotDir;
+        };
+        for ent in dir {
+            let Ok(ent) = ent else {
+                continue;
+            };
+            if ent.path().file_name() == Some(OsStr::new("__init__.er")) {
+                return DirKind::ErgModule;
+            } else if ent.path().file_name() == Some(OsStr::new("__init__.py")) {
+                return DirKind::PyModule;
+            }
+        }
+        DirKind::Other
+    }
+}
+
+impl DirKind {
+    pub const fn is_erg_module(&self) -> bool {
+        matches!(self, DirKind::ErgModule)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum FileKind {
+    InitEr,
+    InitPy,
+    Er,
+    Py,
+    Other,
+    NotFile,
+}
+
+impl From<&Path> for FileKind {
+    fn from(path: &Path) -> Self {
+        if path.is_file() {
+            match path.file_name() {
+                Some(name) if name == OsStr::new("__init__.er") => FileKind::InitEr,
+                Some(name) if name == OsStr::new("__init__.py") => FileKind::InitPy,
+                Some(name) if name.to_string_lossy().ends_with(".er") => FileKind::Er,
+                Some(name) if name.to_string_lossy().ends_with(".py") => FileKind::Py,
+                _ => FileKind::Other,
+            }
+        } else {
+            FileKind::NotFile
+        }
+    }
+}
+
+impl FileKind {
+    pub const fn is_init_er(&self) -> bool {
+        matches!(self, FileKind::InitEr)
+    }
+    pub const fn is_simple_erg_file(&self) -> bool {
+        matches!(self, FileKind::Er)
+    }
+}
+
 pub fn is_cur_dir<P: AsRef<Path>>(path: P) -> bool {
     path.as_ref()
         .components()

crates/erg_compiler/context/inquire.rs

@@ -2455,6 +2455,12 @@ impl Context {
         }
     }
 
+    pub(crate) fn get_mod_with_path(&self, path: &Path) -> Option<&Context> {
+        (self.cfg.input.path() == Some(path)) // module itself
+            .then_some(self)
+            .or(self.mod_cache().get(path).map(|ent| &ent.module.context))
+    }
+
     // FIXME: 現在の実装だとimportしたモジュールはどこからでも見れる
     pub(crate) fn get_mod(&self, name: &str) -> Option<&Context> {
         if name == "module" && ERG_MODE {
@@ -2463,15 +2469,15 @@ impl Context {
             self.get_builtins()
         } else {
             let t = self.get_var_info(name).map(|(_, vi)| &vi.t)?;
-            self.get_mod_from_t(t)
+            self.get_mod_with_t(t)
         }
     }
 
-    pub fn get_mod_from_t(&self, mod_t: &Type) -> Option<&Context> {
-        self.get_ctx_from_path(&self.get_path_from_mod_t(mod_t)?)
+    pub fn get_mod_with_t(&self, mod_t: &Type) -> Option<&Context> {
+        self.get_ctx_from_path(&self.get_path_with_mod_t(mod_t)?)
     }
 
-    pub fn get_path_from_mod_t(&self, mod_t: &Type) -> Option<PathBuf> {
+    pub fn get_path_with_mod_t(&self, mod_t: &Type) -> Option<PathBuf> {
         let tps = mod_t.typarams();
         let Some(TyParam::Value(ValueObj::Str(path))) = tps.get(0) else {
             return None;

crates/erg_compiler/context/register.rs

@@ -10,6 +10,7 @@ use erg_common::consts::PYTHON_MODE;
 use erg_common::env::is_pystd_main_module;
 use erg_common::erg_util::BUILTIN_ERG_MODS;
 use erg_common::levenshtein::get_similar_name;
+use erg_common::pathutil::{DirKind, FileKind};
 use erg_common::python_util::BUILTIN_PYTHON_MODS;
 use erg_common::set::Set;
 use erg_common::traits::{Locational, Stream};
@@ -931,7 +932,9 @@ impl Context {
         let Ok(mod_name) = hir::Literal::try_from(mod_name.token.clone()) else {
             return Ok(());
         };
-        let res = self.import_mod(call.additional_operation().unwrap(), &mod_name);
+        let res = self
+            .import_mod(call.additional_operation().unwrap(), &mod_name)
+            .map(|_path| ());
         let arg = TyParam::Value(ValueObj::Str(
             mod_name.token.content.replace('\"', "").into(),
         ));
@@ -946,14 +949,14 @@ impl Context {
                 params: vec![arg],
             }
         };
-        let Some(ident) = def.sig.ident() else { return Ok(()) };
+        let Some(ident) = def.sig.ident() else { return res };
         let Some((_, vi)) = self.get_var_info(ident.inspect()) else {
-            return Ok(());
+            return res;
         };
         if let Some(_fv) = vi.t.as_free() {
             vi.t.link(&typ);
         }
-        res.map(|_| ())
+        res
     }
 
     pub(crate) fn preregister_def(&mut self, def: &ast::Def) -> TyCheckResult<()> {
@@ -1807,24 +1810,73 @@ impl Context {
     }
 
     fn import_erg_mod(&self, __name__: &Str, loc: &impl Locational) -> CompileResult<PathBuf> {
-        let mod_cache = self.mod_cache();
         let path = match self.cfg.input.resolve_real_path(Path::new(&__name__[..])) {
             Some(path) => path,
             None => {
                 return Err(self.import_err(__name__, loc));
             }
         };
-        // module itself
-        if self.cfg.input.path() == Some(path.as_path()) {
-            return Ok(path);
-        }
+        self.check_mod_vis(path.as_path(), __name__, loc)?;
         if let Some(referrer) = self.cfg.input.path() {
             let graph = &self.shared.as_ref().unwrap().graph;
             graph.inc_ref(referrer, path.clone());
         }
-        if mod_cache.get(&path).is_some() {
+        if self.get_mod_with_path(&path).is_some() {
             return Ok(path);
         }
+        self.build_erg_mod(path, __name__, loc)
+    }
+
+    /// If the path is like `foo/bar`, check if `bar` is a public module (the definition is in `foo/__init__.er`)
+    fn check_mod_vis(
+        &self,
+        path: &Path,
+        __name__: &Str,
+        loc: &impl Locational,
+    ) -> CompileResult<()> {
+        if let Some(parent) = path.parent() {
+            if FileKind::from(path).is_simple_erg_file() && DirKind::from(parent).is_erg_module() {
+                let parent = parent.join("__init__.er");
+                let parent_module = if let Some(parent) = self.get_mod_with_path(&parent) {
+                    Some(parent)
+                } else {
+                    // TODO: This error should not be discarded, but the later processing should also continue while generating the error
+                    self.build_erg_mod(parent.clone(), __name__, loc)?;
+                    self.get_mod_with_path(&parent)
+                };
+                if let Some(parent_module) = parent_module {
+                    let import_err = || {
+                        TyCheckErrors::from(TyCheckError::import_error(
+                            self.cfg.input.clone(),
+                            line!() as usize,
+                            format!("module `{__name__}` is not public"),
+                            loc.loc(),
+                            self.caused_by(),
+                            None,
+                            None,
+                        ))
+                    };
+                    let mod_name = path.file_stem().unwrap_or_default().to_string_lossy();
+                    if let Some((_, vi)) = parent_module.get_var_info(&mod_name) {
+                        if !vi.vis.compatible(&ast::AccessModifier::Public, self) {
+                            return Err(import_err());
+                        }
+                    } else {
+                        return Err(import_err());
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn build_erg_mod(
+        &self,
+        path: PathBuf,
+        __name__: &Str,
+        loc: &impl Locational,
+    ) -> CompileResult<PathBuf> {
+        let mod_cache = self.mod_cache();
         let mut cfg = self.cfg.inherit(path.clone());
         let src = cfg
             .input
@@ -1839,15 +1891,15 @@ impl Context {
                     Some(artifact.object),
                     builder.pop_mod_ctx().unwrap(),
                 );
+                Ok(path)
             }
             Err(artifact) => {
                 if let Some(hir) = artifact.object {
                     mod_cache.register(path, Some(hir), builder.pop_mod_ctx().unwrap());
                 }
-                return Err(artifact.errors);
+                Err(artifact.errors)
             }
         }
-        Ok(path)
     }
 
     fn similar_builtin_py_mod_name(&self, name: &Str) -> Option<Str> {
@@ -1974,6 +2026,16 @@ impl Context {
         if py_mod_cache.get(&path).is_some() {
             return Ok(path);
         }
+        self.build_decl_mod(path, __name__, loc)
+    }
+
+    fn build_decl_mod(
+        &self,
+        path: PathBuf,
+        __name__: &Str,
+        loc: &impl Locational,
+    ) -> CompileResult<PathBuf> {
+        let py_mod_cache = self.py_mod_cache();
         let mut cfg = self.cfg.inherit(path.clone());
         let src = cfg
             .input
@@ -1988,15 +2050,15 @@ impl Context {
             Ok(artifact) => {
                 let ctx = builder.pop_mod_ctx().unwrap();
                 py_mod_cache.register(path.clone(), Some(artifact.object), ctx);
+                Ok(path)
             }
             Err(artifact) => {
                 if let Some(hir) = artifact.object {
                     py_mod_cache.register(path, Some(hir), builder.pop_mod_ctx().unwrap());
                 }
-                return Err(artifact.errors);
+                Err(artifact.errors)
             }
         }
-        Ok(path)
     }
 
     pub fn del(&mut self, ident: &hir::Identifier) -> CompileResult<()> {

doc/EN/syntax/26_module.md

@@ -42,12 +42,19 @@ Now the `bar` directory is recognized as a module. If the only file in `bar` is
 └─┬ bar
   ├─ __init__.er
   ├─ baz.er
-  └─ qux.er
+  └─┬ qux
+    └─ __init__.er
+```
+
+```python
+# bar/__init__.er
+.baz = import "./baz"
+.qux = import "./qux"
 ```
 
 From outside the `bar` directory, you can use like the following.
 
-```erg
+```python
 bar = import "bar"
 
 bar.baz.p!()
@@ -55,11 +62,12 @@ bar.qux.p!()
 ```
 
 `__init__.er` is not just a marker that makes a directory as a module, it also controls the visibility of the module.
+Unlike Python, Erg modules are not importable by default.
 
-```erg
+```python
 # __init__.er
 
-# `. /` points to the current directory. It can be omitted
+# `./` points to the current directory. It can be omitted
 .baz = import ". /baz"
 qux = import ". /qux"
 

doc/JA/syntax/26_module.md

@@ -44,7 +44,14 @@ assert foo.i == 1
 └─┬ bar
   ├─ __init__.er
   ├─ baz.er
-  └─ qux.er
+  └─┬ qux
+    └─ __init__.er
+```
+
+```python
+# bar/__init__.er
+.baz = import "./baz"
+.qux = import "./qux"
 ```
 
 `bar`ディレクトリの外側からは以下のようにして使用できます。
@@ -57,6 +64,7 @@ bar.qux.p!()
 ```
 
 `__init__.er`は単にディレクトリをモジュールとして機能させるだけのマーカーではなく、モジュールの可視性を制御する役割も持ちます。
+Pythonとは違い、Ergのモジュールはデフォルトではインポートできないようになっています。
 
 ```python
 # __init__.er

tests/should_err/foo/__init__.er

@@ -0,0 +1 @@
+.bar = import "./bar"

tests/should_err/foo/bar.er

@@ -0,0 +1 @@
+.i = 1

tests/should_err/foo/baz/__init__.er

@@ -0,0 +1 @@
+.i = 1

tests/should_err/foo/qux.er

@@ -0,0 +1 @@
+.i = 1

tests/should_err/import.er

@@ -0,0 +1,4 @@
+_ = import "foo" # OK
+_ = import "foo/bar" # OK
+_ = import "foo/baz" # ERR
+_ = import "foo/qux" # ERR

tests/test.rs

@@ -283,6 +283,11 @@ fn exec_impl_err() -> Result<(), ()> {
     expect_failure("tests/should_err/impl.er", 2, 2)
 }
 
+#[test]
+fn exec_import_err() -> Result<(), ()> {
+    expect_failure("tests/should_err/import.er", 0, 2)
+}
+
 #[test]
 fn exec_infer_union_array() -> Result<(), ()> {
     expect_failure("tests/should_err/infer_union_array.er", 2, 1)