Warn when emitting code which uses Var indirection (#306)

Author: chrisrink10

src/basilisp/cli.py

@@ -66,13 +66,23 @@ def bootstrap_repl(which_ns: str) -> types.ModuleType:
               is_flag=True,
               envvar='BASILISP_WARN_ON_SHADOWED_VAR',
               help='if provided, emit warnings if a Var name is shadowed by a local name')
-def repl(default_ns, use_var_indirection, warn_on_shadowed_name, warn_on_shadowed_var):
+@click.option('--warn-on-var-indirection',
+              default=True,
+              is_flag=True,
+              envvar='BASILISP_WARN_ON_VAR_INDIRECTION',
+              help='if provided, emit warnings if a Var reference cannot be direct linked')
+def repl(default_ns,
+         use_var_indirection,
+         warn_on_shadowed_name,
+         warn_on_shadowed_var,
+         warn_on_var_indirection):
     basilisp.init()
     repl_module = bootstrap_repl(default_ns)
     ctx = compiler.CompilerContext(
         {compiler.USE_VAR_INDIRECTION: use_var_indirection,
          compiler.WARN_ON_SHADOWED_NAME: warn_on_shadowed_name,
-         compiler.WARN_ON_SHADOWED_VAR: warn_on_shadowed_var})
+         compiler.WARN_ON_SHADOWED_VAR: warn_on_shadowed_var,
+         compiler.WARN_ON_VAR_INDIRECTION: warn_on_var_indirection})
     ns_var = runtime.set_current_ns(default_ns)
     eof = object()
     while True:
@@ -128,18 +138,25 @@ def repl(default_ns, use_var_indirection, warn_on_shadowed_name, warn_on_shadowe
               is_flag=True,
               envvar='BASILISP_WARN_ON_SHADOWED_VAR',
               help='if provided, emit warnings if a Var name is shadowed by a local name')
+@click.option('--warn-on-var-indirection',
+              default=True,
+              is_flag=True,
+              envvar='BASILISP_WARN_ON_VAR_INDIRECTION',
+              help='if provided, emit warnings if a Var reference cannot be direct linked')
 def run(file_or_code,  # pylint: disable=too-many-arguments
         code,
         in_ns,
         use_var_indirection,
         warn_on_shadowed_name,
-        warn_on_shadowed_var):
+        warn_on_shadowed_var,
+        warn_on_var_indirection):
     """Run a Basilisp script or a line of code, if it is provided."""
     basilisp.init()
     ctx = compiler.CompilerContext(
         {compiler.USE_VAR_INDIRECTION: use_var_indirection,
          compiler.WARN_ON_SHADOWED_NAME: warn_on_shadowed_name,
-         compiler.WARN_ON_SHADOWED_VAR: warn_on_shadowed_var})
+         compiler.WARN_ON_SHADOWED_VAR: warn_on_shadowed_var,
+         compiler.WARN_ON_VAR_INDIRECTION: warn_on_var_indirection})
     eof = object()
 
     with runtime.ns_bindings(in_ns) as ns:

src/basilisp/lang/compiler.py

@@ -42,6 +42,7 @@
 USE_VAR_INDIRECTION = 'use_var_indirection'
 WARN_ON_SHADOWED_NAME = 'warn_on_shadowed_name'
 WARN_ON_SHADOWED_VAR = 'warn_on_shadowed_var'
+WARN_ON_VAR_INDIRECTION = 'warn_on_var_indirection'
 
 _BUILTINS_NS = 'builtins'
 _CORE_NS = 'basilisp.core'
@@ -185,6 +186,12 @@ def warn_on_shadowed_var(self) -> bool:
         supersedes the value of this flag."""
         return self.warn_on_shadowed_name or self._opts.entry(WARN_ON_SHADOWED_VAR, True)
 
+    @property
+    def warn_on_var_indirection(self) -> bool:
+        """If True, warn when a Var reference cannot be direct linked (iff
+        use_var_indirection is False).."""
+        return not self.use_var_indirection and self._opts.entry(WARN_ON_VAR_INDIRECTION, True)
+
     @property
     def recur_point(self):
         return self._recur_points[-1]
@@ -1699,6 +1706,9 @@ def _sym_ast(ctx: CompilerContext, form: sym.Symbol) -> ASTStream:
         return
 
     # If we couldn't find the symbol anywhere else, generate a Var.find call
+    # and issue a warning if warn_on_var_indirection is active.
+    if ctx.warn_on_var_indirection:
+        logger.warning(f"could not resolve a direct link to Var '{form}'")
     yield _node(ast.Attribute(
         value=ast.Call(func=_FIND_VAR_FN_NAME, args=[base_sym], keywords=[]),
         attr='value',

tests/basilisp/compiler_test.py

@@ -868,6 +868,17 @@ def test_try_catch(capsys, ns: runtime.Namespace):
     assert "neither\n" == captured.out
 
 
+def test_warn_on_var_indirection(ns: runtime.Namespace):
+    with mock.patch('basilisp.lang.compiler.logger') as logger:
+        lcompile("(fn [] m)",
+                 ctx=compiler.CompilerContext({compiler.WARN_ON_VAR_INDIRECTION: False}))
+        logger.warning.assert_not_called()
+
+    with mock.patch('basilisp.lang.compiler.logger') as logger:
+        lcompile("(fn [] m)")
+        logger.warning.assert_called_once_with("could not resolve a direct link to Var 'm'")
+
+
 def test_unquote(ns: runtime.Namespace):
     with pytest.raises(runtime.RuntimeException):
         lcompile("~s")