From 1ec186e5bf74ad67a29e97e4543f81ef04af9c67 Mon Sep 17 00:00:00 2001
From: Mike Fikes <mike@fikesfarm.com>
Date: Mon, 19 Nov 2018 22:08:09 -0500
Subject: [PATCH] Add requiring-resolve

Fixes #835
---
 CHANGELOG.md                                      |  2 ++
 planck-cljs/src/planck/core.cljs                  | 14 ++++++++++++++
 planck-cljs/src/planck/repl.cljs                  | 10 +++++++++-
 planck-cljs/test/planck/core_test.cljs            |  4 ++++
 planck-cljs/test/planck/requiring_resolve_ns.cljs |  3 +++
 site/src/planck-core.md                           | 11 +++++++++++
 6 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 planck-cljs/test/planck/requiring_resolve_ns.cljs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f0d4b01f..153c1fd1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 All notable changes to this project will be documented in this file. This change log follows the conventions of [keepachangelog.com](http://keepachangelog.com/).
 
 ## [Unreleased]
+### Added
+- Add `requiring-resolve` ([#835](https://github.com/mfikes/planck/issues/835))
 
 ## [2.19.0] - 2018-11-02
 ### Changed
diff --git a/planck-cljs/src/planck/core.cljs b/planck-cljs/src/planck/core.cljs
index ee9bd051..35d67905 100644
--- a/planck-cljs/src/planck/core.cljs
+++ b/planck-cljs/src/planck/core.cljs
@@ -393,6 +393,20 @@
   :args (s/cat :sym symbol?)
   :ret (s/nilable var?))
 
+(defn requiring-resolve
+  "Resolves namespace-qualified sym per 'resolve'. If initial resolve
+  fails, attempts to require sym's namespace and retries."
+  [sym]
+  (if (qualified-symbol? sym)
+    (or (resolve sym)
+        (do (eval `(require '~(-> sym namespace symbol)))
+            (resolve sym)))
+    (throw (js/Error. (str "Not a qualified symbol: " sym)))))
+
+(s/fdef requiring-resolve
+  :args (s/cat :sym qualified-symbol?)
+  :ret (s/nilable var?))
+
 (defn find-var
   "Returns the global var named by the namespace-qualified symbol, or
   nil if no var with that name."
diff --git a/planck-cljs/src/planck/repl.cljs b/planck-cljs/src/planck/repl.cljs
index 46e5ed1f..191165b6 100644
--- a/planck-cljs/src/planck/repl.cljs
+++ b/planck-cljs/src/planck/repl.cljs
@@ -2093,7 +2093,15 @@
 
 (defn- ns-resolve
   [ns sym]
-  (eval `(~'var ~sym) ns))
+  (let [result (atom nil)]
+    (binding [ana/*cljs-warnings* (zipmap (keys ana/*cljs-warnings*) (repeat false))]
+      (cljs/eval st `(~'var ~sym)
+        {:ns      ns
+         :context :expr}
+        (fn [{:keys [value error]}]
+          (when-not error
+            (reset! result value)))))
+    @result))
 
 (defn- resolve
   [sym]
diff --git a/planck-cljs/test/planck/core_test.cljs b/planck-cljs/test/planck/core_test.cljs
index 1f4244d2..ae424e9e 100644
--- a/planck-cljs/test/planck/core_test.cljs
+++ b/planck-cljs/test/planck/core_test.cljs
@@ -146,3 +146,7 @@
 (deftest load-string-test
   (is (= 3 (planck.core/load-string "1 2 3")))
   (is (= "hi" (with-out-str (planck.core/load-string "1 (print \"hi\") 2")))))
+
+(deftest requiring-resolve-test
+  (is (nil? (planck.core/resolve 'planck.requiring-resolve-ns/a)))
+  (is (= 3 @(planck.core/requiring-resolve 'planck.requiring-resolve-ns/a))))
diff --git a/planck-cljs/test/planck/requiring_resolve_ns.cljs b/planck-cljs/test/planck/requiring_resolve_ns.cljs
new file mode 100644
index 00000000..fef6a91d
--- /dev/null
+++ b/planck-cljs/test/planck/requiring_resolve_ns.cljs
@@ -0,0 +1,3 @@
+(ns planck.requiring-resolve-ns)
+
+(def a 3)
diff --git a/site/src/planck-core.md b/site/src/planck-core.md
index 8deb1f96..31966330 100644
--- a/site/src/planck-core.md
+++ b/site/src/planck-core.md
@@ -31,6 +31,7 @@ _Vars_
 [read-line](#read-line)<br/>
 [read-password](#read-password)<br/>
 [read-string](#read-string)<br/>
+[requiring-resolve](#requiring-resolve)<br/>
 [resolve](#resolve)<br/>
 [sleep](#sleep)<br/>
 [slurp](#slurp)<br/>
@@ -262,6 +263,16 @@ Spec<br/>
 Spec<br/>
  _args_: `(alt :unary (cat :s string?) :binary (cat :opts map? :s string?))`<br/><br/>
 
+### <a name="requiring-resolve"></a>requiring-resolve
+`([sym])`
+
+  Resolves namespace-qualified sym per [`resolve`](#resolve). If initial resolve
+  fails, attempts to `require` `sym`'s namespace and retries.
+
+Spec<br/>
+ _args_: `(cat :sym qualified-symbol?)`<br/>
+ _ret_: `(nilable var?)`<br/>
+ 
 ### <a name="resolve"></a>resolve
 `([sym])`