Support imported vars (e.g. by potemkin) in location analysis (#508)

By considering `:file` on var meta in location analysis. Previously we would not find a location for vars where the namespace did not match the source file. As we're not caching negative findings this can speed up analysis for deps with a large number of imported vars significantly.

Author: mk

CHANGELOG.md

@@ -24,6 +24,8 @@ Changes can be:
 
 * 🍒 Add support for cherry as an alternative to sci to evaluate `:render-fn`s. You can change it per form (using form metadata or viewer opts) or doc-wide (using ns metadata) with `{:nextjournal.clerk/render-evaluator :cherry}`.
 
+* 🏳️‍🌈 Syntax highlighting for code listings in all [languages supported by codemirror](https://github.com/codemirror/language-data) ([#500](https://github.com/nextjournal/clerk/issues/500)).
+
 * ⭐️ Adds support for customization of viewer options
 
   Support both globally (via ns metadata or a settings marker) or locally (via form metadata or the viewer options map).
@@ -42,7 +44,9 @@ Changes can be:
 
 * 💫 Support non-evaluated clojure code listings in markdown documents by specifying `{:nextjournal.clerk/code-listing true}` after the language ([#482](https://github.com/nextjournal/clerk/issues/482)).
 
-* 🏳️‍🌈 Syntax highlighting for code listings in all [languages supported by codemirror](https://github.com/codemirror/language-data) ([#500](https://github.com/nextjournal/clerk/issues/500)).
+* 💫 Support imported vars (e.g. by potemkin) in location analysis
+
+    By considering `:file` on var meta in location analysis. Previously we would not find a location for vars where the namespace did not match the source file. As we're not caching negative findings this can speed up analysis for deps with a large number of imported vars significantly.
 
 * 🐜 Turn off analyzer pass for validation of `:type` tags, fixes [#488](https://github.com/nextjournal/clerk/issues/488) @craig-latacora
 

deps.edn

@@ -68,6 +68,8 @@
                                org.clojure/data.csv {:mvn/version "1.0.0"}
                                hickory/hickory {:mvn/version "0.7.1"}
                                sicmutils/sicmutils {:mvn/version "0.20.0"}
+                               io.github.mentat-collective/emmy {:git/sha "b98fef51d80d3edcff3100562b929f9980ff34d7"
+                                                                 :exclusions [org.babashka/sci]}
                                io.github.nextjournal/clerk-slideshow {:git/sha "0e6e890fd4f862fa3535290cb7e29591c6e0ec85"}}}
 
            :build {:deps {io.github.nextjournal/clerk {:local/root "."}

notebooks/emmy.clj

@@ -0,0 +1,33 @@
+(ns emmy-repro
+  (:require [emmy.env :as e]
+            [emmy.mechanics.lagrange]))
+
+;; ## BUG 1:
+
+;; This notebook takes close to 2 seconds to evaluate:
+
+;; Clerk evaluated '/Users/sritchie/code/clj/clerk-demo/notebooks/emmy_repro.clj' in 1853.674042ms.
+
+;; For the final Langrangian in generalized coordinates (the angles of each
+;; segment) by composing `L-rect` with a properly transformed `angles->rect`
+;; coordinate transform!
+
+;; ## BUG 2:
+;;
+;; The following form:
+
+#_
+(let [L (emmy.mechanics.lagrange/L-pendulum 'g 'm 'l)]
+  (((e/Lagrange-equations L)
+    (e/literal-function 'theta_1))
+   't))
+
+;; Evaluates to this:
+(e/literal-number
+ '(- (* 1/2 m 2 l (((expt D 2) theta_1) t) l) (* g m l (- (sin (theta_1 t))))))
+
+
+;; But if I include it in a notebook, I get this:
+
+;; Execution error (NullPointerException) at clojure.tools.analyzer.jvm.utils/members* (utils.clj:272).
+;; Cannot invoke "java.lang.Class.getName()" because the return value of "clojure.lang.IFn.invoke(Object)" is null

src/nextjournal/clerk/analyzer.clj

@@ -406,6 +406,14 @@
                 [".clj" ".cljc"]))
         (cp/classpath-directories)))
 
+(defn var->file [var]
+  (when-let [file-from-var (-> var meta :file)]
+    (some (fn [classpath-dir]
+            (let [path (str classpath-dir fs/file-separator file-from-var)]
+              (when (fs/exists? path)
+                path)))
+          (cp/classpath-directories))))
+
 (defn normalize-filename [f]
   (if (fs/windows?)
     (-> f fs/normalize fs/unixify)
@@ -441,14 +449,27 @@
 #_(symbol->jar 'io.methvin.watcher.PathUtils/cast)
 #_(symbol->jar 'java.net.http.HttpClient/newHttpClient)
 
+(defn var->location [var]
+  (when-let [file (:file (meta var))]
+    (if (fs/absolute? file)
+      (when (fs/exists? file)
+        (fs/relativize (fs/cwd) (fs/file file)))
+      (when-let [resource (io/resource file)]
+        (let [protocol (.getProtocol resource)]
+          (or (and (= "jar" protocol)
+                   (second (re-find #"^file:(.*)!" (.getFile resource))))
+              (and (= "file" protocol)
+                   (.getFile resource))))))))
 
 (defn find-location [sym]
   (if (deref? sym)
     (find-location (second sym))
-    (if-let [ns (and (qualified-symbol? sym) (-> sym namespace symbol find-ns))]
-      (or (ns->file ns)
-          (ns->jar ns))
-      (symbol->jar sym))))
+    (or (some-> sym resolve var->location)
+        (if-let [ns (and (qualified-symbol? sym) (-> sym namespace symbol find-ns))]
+          (or (ns->file ns)
+              (ns->jar ns))
+          (symbol->jar sym)))))
+
 
 #_(find-location `inc)
 #_(find-location '@nextjournal.clerk.webserver/!doc)