Limit core rewrites to core namespace

Apply portable core definition replacements only while rewriting the
clojure.core namespace.
Prevent user functions with names such as read from being replaced by
unrelated core compatibility implementations.
Add focused rewrite coverage for a non-core read function.

Author: ingydotnet

Makefile

@@ -217,9 +217,21 @@ vet: $(GO)
 	go vet ./...
 
 # vet is disabled until we fix errors in generated code
-test: test-aot-runtime test-aot-codegen test-glj test-repl-wasm test-repl-bsd  # vet
+test: \
+  test-rewrite-core \
+  test-aot-runtime \
+  test-aot-codegen \
+  test-glj \
+  test-repl-wasm \
+  test-repl-bsd  # vet
 	($(MAKE) test-suite v=1 || $(MAKE) test-suite v=1) || $(MAKE) test-suite v=1
 
+test-rewrite-core: $(CLOJURE)
+	HOME="$(LOCAL-HOME)" CLJ="$(CLOJURE)" \
+	  scripts/rewrite-core/run.sh \
+	  scripts/rewrite-core/test/non-core.clj | \
+	  cmp - scripts/rewrite-core/test/non-core.glj
+
 TEST-COMPARE-LOAD := $(shell \
 	processors=$$(getconf _NPROCESSORS_ONLN 2>/dev/null || echo 2); \
 	awk -v processors="$$processors" \

scripts/rewrite-core/rewrite.clj

@@ -5,6 +5,18 @@
 
 (def zloc (z/of-string (slurp (first *command-line-args*))))
 
+(defn source-namespace [zloc]
+  (loop [zloc zloc]
+    (if (z/end? zloc)
+      nil
+      (let [form (when (z/sexpr-able? zloc) (z/sexpr zloc))]
+        (if (and (list? form) (= 'ns (first form)))
+          (second form)
+          (recur (z/next zloc)))))))
+
+(def core-source?
+  (= 'clojure.core (source-namespace zloc)))
+
 ;; remove until we're at the end of all forms
 (defn skip-n [zloc n]
   ;; apply z/right n times
@@ -509,8 +521,9 @@
 
 (def replacements
   (concat
-    (map (fn [[name form]] (definition-replace name form))
-         portable-core-definitions)
+    (when core-source?
+      (map (fn [[name form]] (definition-replace name form))
+           portable-core-definitions))
     ;; Simple mappings from data structures
     (create-simple-replacements namespace-mappings)
     (create-simple-replacements type-mappings)

scripts/rewrite-core/test/non-core.clj

@@ -0,0 +1,5 @@
+(ns rewrite-test.non-core
+  (:refer-clojure :exclude [read]))
+
+(defn read [path]
+  (os.ReadFile path))

scripts/rewrite-core/test/non-core.glj

@@ -0,0 +1,5 @@
+(ns rewrite-test.non-core
+  (:refer-clojure :exclude [read]))
+
+(defn read [path]
+  (os.ReadFile path))