Add open function and re module to DSL (#917)

* Add open function and re module to DSL

doc/en/dsl.md

@@ -8,7 +8,9 @@ functions and keywords, include but not limited to:
 - `exec`, `execfile` and `eval` To improve the consistency of BUILD files.
 - `import` Use the built-in `blade` module instead
 - `print` Use the functions in `blade.console` module instead
-- `open`
+
+Some builtin functions are restricted.
+- `open` only read mode is allowed
 
 To use some common additional functions, such as `os.path.join`, you need to use similar sub-modules in the `blade` module.
 If you want to add more appropriate modules, please make an Issue.
@@ -26,6 +28,7 @@ The global Blade API module, accessed through `blade.`, includes:
 - `current_target_dir()` function: The output directory where the current BUILD file is located corresponds to (relative to the root directory of the workspace)
 - `config` submodule: Read blade configuration information
 - `console` submodule: Output diagnostic information
+- `re` submodule: The python regex library
 - `path` submodule: a Restricted subset of `os.path`
 
 ### `blade.config` Submodule

doc/zh_CN/dsl.md

@@ -7,7 +7,10 @@
 - `exec`，`execfile`，`eval` 提高构建文件的一致性。
 - `import` 请用 `blade` 的子模块。
 - `print` 请用 `blade.console` 里的函数代替。
-- `open`
+
+某些函数功能则有限制：
+
+- `open` 只允许读模式访问
 
 即使用 python 2 来运行 Blade，你也应当尽量采用反向移植的 python 3 的语法。
 
@@ -24,6 +27,7 @@
 - `current_target_dir()` 函数：当前 BUILD 文件所在的目录对应于（相对于 workspace 的根目录）
 - `config` 子模块：读取 blade 的配置信息
 - `console` 子模块：输出诊断信息
+- `re` 子模块：正则表达式
 - `path` 子模块：`os.path` 的一个受限制的子集
 
 ### `blade.config` 模块

src/blade/dsl_api.py

@@ -9,6 +9,7 @@
 """
 
 import os
+import re
 import types
 
 import blade
@@ -97,6 +98,7 @@ def _safe_blade_module():
     module.current_target_dir = blade.current_target_dir
     module.environ = os.environ
     module.path = _safe_path_module()
+    module.re = re
     module.util = _safe_util_module()
     module.workspace = _safe_workspace_module()
     return module

src/blade/restricted.py

@@ -132,7 +132,6 @@
     'exec',
     'execfile',
     'eval',
-    'open',
 ]
 
 
@@ -145,6 +144,24 @@ def wrapper(*args, **kwargs):
     return wrapper
 
 
+def _open(name, mode=None, buffering=None):
+    """A Readonly open function"""
+    if mode is None and buffering is None:
+        return open(name)
+    if mode:
+        if 'w' in mode or 'a' in mode:
+            raise ValueError('"open" only allow readonly mode')
+    if buffering is None:
+        return open(name, mode)
+    return open(name, mode, buffering)
+
+
+# Replace some functions to better help users know how to deal with.
+_REPLACED_FUNCTIONS = {
+    'open': _open,
+}
+
+
 def _make_safe_buildins():
     safe_builtins = {}
 
@@ -161,6 +178,9 @@ def _make_safe_buildins():
             user_friend_name = name
         safe_builtins[name] = _make_forbidden_wrapper(user_friend_name)
 
+    for name, func in _REPLACED_FUNCTIONS.items():
+        safe_builtins[name] = func
+
     return safe_builtins