give only a warning if requiring a file for using/import does not yie…

…ld a module

fixes #4492

for #4600, don't do any requires for relative imports. we might add
some behavior here in the future, but for now looking for files in
global locations for relative module paths is clearly wrong.

src/toplevel.c

@@ -233,12 +233,12 @@ static jl_module_t *eval_import_path_(jl_array_t *args, int retrying)
             if (mb->owner == m || mb->imported) {
                 m = (jl_module_t*)mb->value;
                 if (m == NULL || !jl_is_module(m))
-                    jl_errorf("invalid module path");
+                    jl_errorf("invalid module path (%s does not name a module)", var->name);
                 break;
             }
         }
         if (m == jl_main_module) {
-            if (!retrying) {
+            if (!retrying && i==1) { // (i==1) => no require() for relative imports
                 if (require_func == NULL && jl_base_module != NULL)
                     require_func = jl_get_global(jl_base_module, jl_symbol("require"));
                 if (require_func != NULL) {
@@ -250,7 +250,13 @@ static jl_module_t *eval_import_path_(jl_array_t *args, int retrying)
                 }
             }
         }
-        jl_errorf("in module path: %s not defined", var->name);
+        if (retrying && require_func) {
+            JL_PRINTF(JL_STDERR, "Warning: requiring \"%s\" did not define a corresponding module.\n", var->name);
+            return NULL;
+        }
+        else {
+            jl_errorf("in module path: %s not defined", var->name);
+        }
     }
 
     for(; i < jl_array_len(args)-1; i++) {
@@ -301,6 +307,7 @@ jl_value_t *jl_toplevel_eval_flex(jl_value_t *e, int fast)
     // handle import, using, importall, export toplevel-only forms
     if (ex->head == importall_sym) {
         jl_module_t *m = eval_import_path(ex->args);
+        if (m==NULL) return jl_nothing;
         jl_sym_t *name = (jl_sym_t*)jl_cellref(ex->args, jl_array_len(ex->args)-1);
         assert(jl_is_symbol(name));
         m = (jl_module_t*)jl_eval_global_var(m, name);
@@ -312,6 +319,7 @@ jl_value_t *jl_toplevel_eval_flex(jl_value_t *e, int fast)
 
     if (ex->head == using_sym) {
         jl_module_t *m = eval_import_path(ex->args);
+        if (m==NULL) return jl_nothing;
         jl_sym_t *name = (jl_sym_t*)jl_cellref(ex->args, jl_array_len(ex->args)-1);
         assert(jl_is_symbol(name));
         jl_module_t *u = (jl_module_t*)jl_eval_global_var(m, name);
@@ -326,6 +334,7 @@ jl_value_t *jl_toplevel_eval_flex(jl_value_t *e, int fast)
 
     if (ex->head == import_sym) {
         jl_module_t *m = eval_import_path(ex->args);
+        if (m==NULL) return jl_nothing;
         jl_sym_t *name = (jl_sym_t*)jl_cellref(ex->args, jl_array_len(ex->args)-1);
         assert(jl_is_symbol(name));
         jl_module_import(jl_current_module, m, name);