Add with-env.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased - ???
+- Add `with-env`
 - Add *module-make-env* dynamic binding
 - Add buffer/format-at
 - Add long form command line options for readable CLI usage

src/boot/boot.janet

@@ -1423,6 +1423,11 @@
       ~(setdyn ,(bindings i) ,(bindings (+ i 1)))))
   ~(,resume (,fiber/new (fn [] ,;dyn-forms ,;body) :p)))
 
+(defmacro with-env
+  `Run a block of code with a given environment table`
+  [env & body]
+  ~(,resume (,fiber/new (fn [] ,;body) : ,env)))
+
 (defmacro with-vars
   ``Evaluates `body` with each var in `vars` temporarily bound. Similar signature to
   `let`, but each binding must be a var.``

test/suite-boot.janet

@@ -976,4 +976,7 @@
 (assert (= () '() (macex '())) "macex ()")
 (assert (= '[] (macex '[])) "macex []")
 
+(assert (= :a (with-env @{:b :a} (dyn :b))) "with-env dyn")
+(assert-error "unknown symbol +" (with-env @{} (eval '(+ 1 2))))
+
 (end-suite)