Add support for auto-resolved namespaces for keywords (#576)

* Add support for auto-resolved namespaces for keywords

* Changelog

* Lint

Author: chrisrink10

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+ * Added support for auto-resolving namespaces for keyword from the current namespace using the `::kw` syntax (#576)
 
 ## [v0.1.dev14] - 2020-06-18
 ### Added

src/basilisp/lang/reader.py

@@ -49,7 +49,7 @@
     IWithMeta,
 )
 from basilisp.lang.obj import seq_lrepr as _seq_lrepr
-from basilisp.lang.runtime import Namespace, Var, lrepr
+from basilisp.lang.runtime import Namespace, Var, get_current_ns, lrepr
 from basilisp.lang.typing import IterableLispForm, LispForm, ReaderForm
 from basilisp.lang.util import munge
 from basilisp.util import Maybe, partition
@@ -835,9 +835,28 @@ def _read_kw(ctx: ReaderContext) -> keyword.Keyword:
     """Return a keyword from the input stream."""
     start = ctx.reader.advance()
     assert start == ":"
+    token = ctx.reader.peek()
+    if token == ":":
+        ctx.reader.advance()
+        should_autoresolve = True
+    else:
+        should_autoresolve = False
+
     ns, name = _read_namespaced(ctx)
     if "." in name:
         raise ctx.syntax_error("Found '.' in keyword name")
+
+    if should_autoresolve:
+        current_ns = get_current_ns()
+        if ns is not None:
+            aliased_ns = current_ns.aliases.get(symbol.symbol(ns))
+            if aliased_ns is None:
+                raise ctx.syntax_error(f"Cannot resolve namespace alias '{ns}'")
+            ns = aliased_ns.name
+        else:
+            ns = current_ns.name
+        return keyword.keyword(name, ns=ns)
+
     return keyword.keyword(name, ns=ns)
 
 
@@ -848,7 +867,7 @@ def _read_meta(ctx: ReaderContext) -> IMeta:
     assert start == "^"
     meta = _read_next_consuming_comment(ctx)
 
-    meta_map: Optional[lmap.Map[LispForm, LispForm]] = None
+    meta_map: Optional[lmap.Map[LispForm, LispForm]]
     if isinstance(meta, symbol.Symbol):
         meta_map = lmap.map({keyword.keyword("tag"): meta})
     elif isinstance(meta, keyword.Keyword):

tests/basilisp/reader_test.py

@@ -245,6 +245,17 @@ def test_kw():
         read_str_first(":dotted.kw")
 
 
+def test_autoresolved_kw(test_ns: str, ns: runtime.Namespace):
+    assert kw.keyword("kw", ns=test_ns) == read_str_first("::kw")
+
+    new_ns = runtime.Namespace(sym.symbol("other.ns"))
+    ns.add_alias(new_ns, sym.symbol("other"))
+    assert kw.keyword("kw", ns="other.ns") == read_str_first("::other/kw")
+
+    with pytest.raises(reader.SyntaxError):
+        read_str_first("::third/kw")
+
+
 def test_literals():
     assert read_str_first("nil") is None
     assert read_str_first("true") is True