Support Reader Conditional syntax (#409)

* Support Reader Conditional syntax

* Fix Reader Conditional splicing

* Merge error

* Updates to allow creation of new venvs

* Clean up

* Some tests

* Some test fixes

* Full tests

* Lisp representation tests

* Fix everything maybe hopefully plz

Author: chrisrink10

Pipfile.lock

@@ -56,6 +56,7 @@ def eval_file(filename: str, ctx: compiler.CompilerContext, module: types.Module
     """Evaluate a file with the given name into a Python module AST node."""
     last = None
     for form in reader.read_file(filename, resolver=runtime.resolve_alias):
+        assert not isinstance(form, reader.ReaderConditional)
         last = compiler.compile_and_exec_form(form, ctx, module)
     return last
 
@@ -64,6 +65,7 @@ def eval_stream(stream, ctx: compiler.CompilerContext, module: types.ModuleType)
     """Evaluate the forms in stdin into a Python module AST node."""
     last = None
     for form in reader.read(stream, resolver=runtime.resolve_alias):
+        assert not isinstance(form, reader.ReaderConditional)
         last = compiler.compile_and_exec_form(form, ctx, module)
     return last
 
@@ -72,6 +74,7 @@ def eval_str(s: str, ctx: compiler.CompilerContext, module: types.ModuleType, eo
     """Evaluate the forms in a string into a Python module AST node."""
     last = eof
     for form in reader.read_str(s, resolver=runtime.resolve_alias, eof=eof):
+        assert not isinstance(form, reader.ReaderConditional)
         last = compiler.compile_and_exec_form(form, ctx, module)
     return last
 

src/basilisp/cli.py

@@ -2172,7 +2172,11 @@
                                          (:eof opts)
                                          (if (= (:eof opts) :eofthrow)
                                            true
-                                           false)))))
+                                           false)
+                                         (:features opts)
+                                         (if (= :preserve (:read-cond opts))
+                                           false
+                                           true)))))
 
 (defn read
   "Read the next form from the stream. If no stream is specified, uses
@@ -2195,7 +2199,11 @@
                                      (:eof opts)
                                      (if (= (:eof opts) :eofthrow)
                                        true
-                                       false))))
+                                       false)
+                                     (:features opts)
+                                     (if (= :preserve (:read-cond opts))
+                                       false
+                                       true))))
   ([stream eof-error? eof-value]
    (first (basilisp.lang.reader/read stream
                                      *resolver*

src/basilisp/core.lpy

@@ -8,11 +8,12 @@
 from functools import lru_cache
 from importlib.abc import MetaPathFinder, SourceLoader
 from importlib.machinery import ModuleSpec
-from typing import List, Mapping, MutableMapping, Optional
+from typing import Iterable, List, Mapping, MutableMapping, Optional, cast
 
 import basilisp.lang.compiler as compiler
 import basilisp.lang.reader as reader
 import basilisp.lang.runtime as runtime
+from basilisp.lang.typing import ReaderForm
 from basilisp.lang.util import demunge
 from basilisp.util import timed
 
@@ -278,7 +279,13 @@ def add_bytecode(bytecode: types.CodeType):
                 all_bytecode.append(bytecode)
 
             logger.debug(f"Reading and compiling Basilisp module '{fullname}'")
-            forms = reader.read_file(filename, resolver=runtime.resolve_alias)
+            # Cast to basic ReaderForm since the reader can never return a reader conditional
+            # form unprocessed in internal usage. There are reader settings which permit
+            # callers to leave unprocessed reader conditionals in the stream, however.
+            forms = cast(
+                Iterable[ReaderForm],
+                reader.read_file(filename, resolver=runtime.resolve_alias),
+            )
             compiler.compile_module(  # pylint: disable=unexpected-keyword-arg
                 forms,
                 compiler.CompilerContext(filename=filename),