Use context managers to change *ns* in tests (#228)

Author: chrisrink10

src/basilisp/cli.py

@@ -99,14 +99,13 @@ def run(file_or_code, code, in_ns):
     """Run a Basilisp script or a line of code, if it is provided."""
     basilisp.init()
     ctx = compiler.CompilerContext()
-    ns_var = runtime.set_current_ns(in_ns)
-    ns: runtime.Namespace = ns_var.value
     eof = object()
 
-    if code:
-        print(compiler.lrepr(eval_str(file_or_code, ctx, ns.module, eof)))
-    else:
-        print(compiler.lrepr(eval_file(file_or_code, ctx, ns.module)))
+    with runtime.ns_bindings(in_ns) as ns:
+        if code:
+            print(compiler.lrepr(eval_str(file_or_code, ctx, ns.module, eof)))
+        else:
+            print(compiler.lrepr(eval_file(file_or_code, ctx, ns.module)))
 
 
 @cli.command(short_help='run tests in a Basilisp project')

src/basilisp/lang/runtime.py

@@ -1,3 +1,4 @@
+import contextlib
 import functools
 import importlib
 import itertools
@@ -755,6 +756,37 @@ def set_current_ns(ns_name: str,
     return ns_var
 
 
+@contextlib.contextmanager
+def ns_bindings(ns_name: str,
+                module: types.ModuleType = None,
+                ns_var_name: str = _NS_VAR_NAME,
+                ns_var_ns: str = _NS_VAR_NS):
+    """Context manager for temporarily changing the value of basilisp.core/*ns*."""
+    symbol = sym.Symbol(ns_name)
+    ns = Namespace.get_or_create(symbol, module=module)
+    ns_var = Maybe(Var.find(sym.Symbol(ns_var_name, ns=ns_var_ns))) \
+        .or_else_raise(lambda: RuntimeException(f"Dynamic Var {sym.Symbol(ns_var_name, ns=ns_var_ns)} not bound!"))
+
+    try:
+        ns_var.push_bindings(ns)
+        yield ns_var.value
+    finally:
+        ns_var.pop_bindings()
+
+
+@contextlib.contextmanager
+def remove_ns_bindings(ns_var_name: str = _NS_VAR_NAME,
+                       ns_var_ns: str = _NS_VAR_NS):
+    """Context manager to pop the most recent bindings for basilisp.core/*ns* after
+    completion of the code under management."""
+    ns_var = Maybe(Var.find(sym.Symbol(ns_var_name, ns=ns_var_ns))) \
+        .or_else_raise(lambda: RuntimeException(f"Dynamic Var {sym.Symbol(ns_var_name, ns=ns_var_ns)} not bound!"))
+    try:
+        yield
+    finally:
+        ns_var.pop_bindings()
+
+
 def get_current_ns(ns_var_name: str = _NS_VAR_NAME,
                    ns_var_ns: str = _NS_VAR_NS) -> Namespace:
     """Get the value of the dynamic variable `*ns*` in the current thread."""