js: Split compilation from execution in some places

In a few places, we need to split up compilation from execution in order
to be able to use new scoping rules for JS evaluation.

In SpiderMonkey 45, you cannot pass in a custom global object anymore to
JS::Evaluate(). Instead, you can either use the context's global object,
or pass in a "scope chain". The scope chain implicitly has the global
object at the end. In our case, we can pass in a scope chain of one object
to get the previous behaviour of gjs_eval_with_scope().

There is also a scope chain variant of JS::Evaluate(), but it does not
take a UTF-8 char * buffer.

When evaluating a script in another compartment, we need to use
JS::CloneAndExecuteScript() since we can't pass in the compartment's global
object either. This also requires a precompiled JSScript.

We have to duplicate the compile options and stripping the shebang line
in gjs_context_eval_file_in_compartment(), and change
gjs_strip_unix_shebang() to take an unsigned length. Not great, but I
think the alternative would cause even more churn.

https://bugzilla.gnome.org/show_bug.cgi?id=781429

4 files changed, 33 insertions, 17 deletions

diff --git a/gjs/coverage.cpp b/gjs/coverage.cpp
index 09a6fc3a..44a11c30 100644
--- a/gjs/coverage.cpp
+++ b/gjs/coverage.cpp
@@ -1298,18 +1298,27 @@ gjs_context_eval_file_in_compartment(GjsContext      *context,
 
     g_object_unref(file);
 
+    int start_line_number = 1;
+    const char *stripped_script = gjs_strip_unix_shebang(script, &script_len,
+                                                         &start_line_number);
+
     JSContext *js_context = (JSContext *) gjs_context_get_native_context(context);
 
     JSAutoCompartment compartment(js_context, compartment_object);
 
-    JS::RootedValue return_value(js_context);
-    if (!gjs_eval_with_scope(js_context,
-                             compartment_object,
-                             script, script_len, filename,
-                             &return_value)) {
+    JS::CompileOptions options(js_context);
+    options.setUTF8(true)
+           .setFileAndLine(filename, start_line_number)
+           .setSourceIsLazy(true);
+    JS::RootedScript compiled_script(js_context);
+    if (!JS::Compile(js_context, compartment_object, options, stripped_script,
+                     script_len, &compiled_script))
+        return false;
+
+    if (!JS::CloneAndExecuteScript(js_context, compartment_object,
+                                   compiled_script)) {
         g_free(script);
         gjs_log_exception(js_context);
-        g_free(script);
         g_set_error(error, GJS_ERROR, GJS_ERROR_FAILED, "Failed to evaluate %s", filename);
         return false;
     }
diff --git a/gjs/jsapi-util.cpp b/gjs/jsapi-util.cpp
index 4d59d595..900b1b48 100644
--- a/gjs/jsapi-util.cpp
+++ b/gjs/jsapi-util.cpp
@@ -867,7 +867,7 @@ gjs_schedule_gc_if_needed (JSContext *context)
  */
 const char *
 gjs_strip_unix_shebang(const char  *script,
-                       gssize      *script_len,
+                       size_t      *script_len,
                        int         *start_line_number_out)
 {
     g_assert(script_len);
@@ -913,12 +913,13 @@ gjs_eval_with_scope(JSContext             *context,
 {
     int start_line_number = 1;
     JSAutoRequest ar(context);
+    size_t real_len = script_len;
 
     if (script_len < 0)
-        script_len = strlen(script);
+        real_len = strlen(script);
 
     script = gjs_strip_unix_shebang(script,
-                                    &script_len,
+                                    &real_len,
                                     &start_line_number);
 
     /* log and clear exception if it's set (should not be, normally...) */
@@ -936,7 +937,13 @@ gjs_eval_with_scope(JSContext             *context,
            .setFileAndLine(filename, start_line_number)
            .setSourceIsLazy(true);
 
-    if (!JS::Evaluate(context, eval_obj, options, script, script_len, retval))
+    JS::RootedScript compiled_script(context);
+    if (!JS::Compile(context, object, options, script, real_len, &compiled_script))
+        return false;
+
+    JS::AutoObjectVector scope_chain(context);
+    scope_chain.append(eval_obj);
+    if (!JS_ExecuteScript(context, scope_chain, compiled_script, retval))
         return false;
 
     gjs_schedule_gc_if_needed(context);
diff --git a/gjs/jsapi-util.h b/gjs/jsapi-util.h
index 718a82f2..e05e12b0 100644
--- a/gjs/jsapi-util.h
+++ b/gjs/jsapi-util.h
@@ -272,7 +272,7 @@ typedef enum {
 } GjsConstString;
 
 const char * gjs_strip_unix_shebang(const char *script,
-                                    gssize     *script_len,
+                                    size_t     *script_len,
                                     int        *new_start_line_number);
 
 /* These four functions wrap JS_GetPropertyById(), etc., but with a
diff --git a/test/gjs-tests.cpp b/test/gjs-tests.cpp
index febfe0eb..f5119e50 100644
--- a/test/gjs-tests.cpp
+++ b/test/gjs-tests.cpp
@@ -330,8 +330,8 @@ static void
 gjstest_test_strip_shebang_no_advance_for_no_shebang(void)
 {
     const char *script = "foo\nbar";
-    gssize     script_len_original = strlen(script);
-    gssize     script_len = script_len_original;
+    size_t script_len_original = strlen(script);
+    size_t script_len = script_len_original;
     int        line_number = 1;
 
     const char *stripped = gjs_strip_unix_shebang(script,
@@ -347,8 +347,8 @@ static void
 gjstest_test_strip_shebang_advance_for_shebang(void)
 {
     const char *script = "#!foo\nbar";
-    gssize     script_len_original = strlen(script);
-    gssize     script_len = script_len_original;
+    size_t script_len_original = strlen(script);
+    size_t script_len = script_len_original;
     int        line_number = 1;
 
     const char *stripped = gjs_strip_unix_shebang(script,
@@ -364,8 +364,8 @@ static void
 gjstest_test_strip_shebang_return_null_for_just_shebang(void)
 {
     const char *script = "#!foo";
-    gssize     script_len_original = strlen(script);
-    gssize     script_len = script_len_original;
+    size_t script_len_original = strlen(script);
+    size_t script_len = script_len_original;
     int        line_number = 1;
 
     const char *stripped = gjs_strip_unix_shebang(script,