CLJS-1515: Self-host: Allow :file key in cljs.js/*load-fn*

Bootstrapped ClojureScript is abstracted away from direct I/O by use of a *load-fn* callback. A
result is that when a namespace is loaded, the :file attribute associated with def s in
[:cljs.analyzer/namespaces 'foo.ns :defs] in the AST is nil, because cljs.analyzer/*cljs-file*
cannot be set to a meaningful value.

This ticket asks for an extension to *load-fn*, allowing a :file key to be optionally included by
cljs.js clients, and for cljs.analyzer/*cljs-file* to be bound to that value in appropriate places
in cljs.js so that the :file info appears in the AST.

One rationale for this :file attribute is that it makes it easier for clients of cljs.js to look up
the file for a def, say, for use when implementing a source REPL special, for example.

Author: arichiardi

src/main/cljs/cljs/js.cljs

@@ -71,6 +71,8 @@
 
   :lang       - the language, :clj or :js
   :source     - the source of the library (a string)
+  :file       - optional, the file path, it will be added to AST's :file keyword
+                (but not in :meta)
   :cache      - optional, if a :clj namespace has been precompiled to :js, can
                 give an analysis cache for faster loads.
   :source-map - optional, if a :clj namespace has been precompiled to :js, can
@@ -246,9 +248,9 @@
                (assert (or (map? resource) (nil? resource))
                  "*load-fn* may only return a map or nil")
                (if resource
-                 (let [{:keys [lang source cache source-map]} resource]
+                 (let [{:keys [lang source cache source-map file]} resource]
                    (condp = lang
-                     :clj (eval-str* bound-vars source name opts
+                     :clj (eval-str* bound-vars source name (assoc opts :cljs-file file)
                             (fn [res]
                               (if (:error res)
                                 (cb res)
@@ -379,9 +381,9 @@
                 (assert (or (map? resource) (nil? resource))
                   "*load-fn* may only return a map or nil")
                 (if resource
-                  (let [{:keys [name lang source]} resource]
+                  (let [{:keys [name lang source file]} resource]
                     (condp = lang
-                      :clj (analyze-str* bound-vars source name opts
+                      :clj (analyze-str* bound-vars source name (assoc opts :cljs-file file)
                              (fn [res]
                                (if-not (:error res)
                                  (analyze-deps bound-vars ana-env lib (next deps) opts cb)
@@ -517,7 +519,8 @@
                  r/*alias-map*          (current-alias-map)
                  r/*data-readers*       (:*data-readers* bound-vars)
                  r/resolve-symbol       resolve-symbol
-                 comp/*source-map-data* (:*sm-data* bound-vars)]
+                 comp/*source-map-data* (:*sm-data* bound-vars)
+                 ana/*cljs-file*        (:cljs-file opts)]
          (let [res (try
                      {:value (r/read {:eof eof :read-cond :allow :features #{:cljs}} rdr)}
                      (catch :default cause
@@ -780,7 +783,8 @@
                  r/*alias-map*          (current-alias-map)
                  r/*data-readers*       (:*data-readers* bound-vars)
                  r/resolve-symbol       resolve-symbol
-                 comp/*source-map-data* (:*sm-data* bound-vars)]
+                 comp/*source-map-data* (:*sm-data* bound-vars)
+                 ana/*cljs-file*        (:cljs-file opts)]
          (let [res (try
                      {:value (r/read {:eof eof :read-cond :allow :features #{:cljs}} rdr)}
                      (catch :default cause

src/test/self/self_host/test.cljs

@@ -2,6 +2,7 @@
   (:require [cljs.test :as test
              :refer-macros [run-tests deftest testing is async]]
             [cljs.js :as cljs]
+            [cljs.analyzer :as ana]
             [clojure.string :as string]
             [cljs.nodejs :as nodejs]))
 
@@ -47,6 +48,27 @@
 (defn elide-env [env ast opts]
   (dissoc ast :env))
 
+(defn var-ast
+  "Given an already derefed compiler state plus the symbols of a
+  namespace and a var (e.g. 'clojure.string and 'trim) , return the var
+  AST representation or nil if not found, probably because not required
+  yet.
+
+  The 1-arity function does the splitting in case of a fully qualified
+  symbol (e.g. 'clojure.string/trim)."
+  ([st sym]
+   (var-ast st (symbol (namespace sym)) (symbol (name sym))))
+  ([st ns-sym sym]
+   (get-in st [:cljs.analyzer/namespaces ns-sym :defs sym])))
+
+(defn file->lang
+  "Converts a file path to a :lang keyword by inspecting the file
+   extension."
+  [file-path]
+  (if (string/ends-with? file-path ".js")
+    :js
+    :clj))
+
 (defn str-evals-to
   "Checks that a string evaluates to an expected value."
   ([st l expected s]
@@ -750,7 +772,7 @@
         (str-evals-to st l [1 1 1 1 1]
           "(let [an-array (int-array 5 0)] (js->clj (amap an-array idx ret (+ 1 (aget an-array idx)))))" {:ns 'foo.core})))))
 
-#_(deftest test-eval-str-with-require
+(deftest test-eval-str-with-require
   (async done
     (let [l (latch 3 done)]
       (cljs/eval-str st