module.system.node.root_relative_dirname lets you configure where r…

…oot relative paths resolve to

Summary:
When we see

```
[options]
module.system.node.allow_root_relative=true
module.system.node.root_relative_dirname=first
module.system.node.root_relative_dirname=second
```

Then we'll resolve `import foo from 'path/to/foo'`

1. First in `<PROJECT_ROOT>/first/path/to/foo.js`
2. Second in `<PROJECT_ROOT>/second/path/to/foo.js`
3. Third in node_modules.

Reviewed By: jbrown215

Differential Revision: D18234623

fbshipit-source-id: f569e599a9fb0191ba959cda89166ab1b77fd758

src/commands/commandUtils.ml

@@ -1282,6 +1282,8 @@ let make_options ~flowconfig_name ~flowconfig ~lazy_mode ~root (options_flags :
       opt_no_saved_state = options_flags.no_saved_state;
       opt_node_resolver_allow_root_relative =
         FlowConfig.node_resolver_allow_root_relative flowconfig;
+      opt_node_resolver_root_relative_dirnames =
+        FlowConfig.node_resolver_root_relative_dirnames flowconfig;
       opt_arch;
       opt_abstract_locations;
       opt_cache_direct_dependents = FlowConfig.cache_direct_dependents flowconfig;

src/commands/config/flowConfig.ml

@@ -93,6 +93,7 @@ module Opts = struct
     no_flowlib: bool;
     node_resolver_allow_root_relative: bool;
     node_resolver_dirnames: string list;
+    node_resolver_root_relative_dirnames: string list;
     recursion_limit: int;
     root_name: string option;
     saved_state_fetcher: Options.saved_state_fetcher;
@@ -191,6 +192,7 @@ module Opts = struct
       no_flowlib = false;
       node_resolver_allow_root_relative = false;
       node_resolver_dirnames = ["node_modules"];
+      node_resolver_root_relative_dirnames = [""];
       recursion_limit = 10000;
       root_name = None;
       saved_state_fetcher = Options.Dummy_fetcher;
@@ -470,6 +472,15 @@ module Opts = struct
             else
               let node_resolver_dirnames = v :: opts.node_resolver_dirnames in
               Ok { opts with node_resolver_dirnames }) );
+      ( "module.system.node.root_relative_dirname",
+        string
+          ~init:(fun opts -> { opts with node_resolver_root_relative_dirnames = [] })
+          ~multiple:true
+          (fun opts v ->
+            let node_resolver_root_relative_dirnames =
+              v :: opts.node_resolver_root_relative_dirnames
+            in
+            Ok { opts with node_resolver_root_relative_dirnames }) );
       ("module.use_strict", boolean (fun opts v -> Ok { opts with modules_are_use_strict = v }));
       ("munge_underscores", boolean (fun opts v -> Ok { opts with munge_underscores = v }));
       ( "name",
@@ -997,7 +1008,7 @@ let is_not_comment =
       (* Line starts with ; *)
         Str.regexp_string "\240\159\146\169";
         (* Line starts with poop emoji *)
-
+      
     ]
   in
   fun (_, line) ->
@@ -1189,6 +1200,8 @@ let node_resolver_allow_root_relative c = c.options.Opts.node_resolver_allow_roo
 
 let node_resolver_dirnames c = c.options.Opts.node_resolver_dirnames
 
+let node_resolver_root_relative_dirnames c = c.options.Opts.node_resolver_root_relative_dirnames
+
 let recursion_limit c = c.options.Opts.recursion_limit
 
 let root_name c = c.options.Opts.root_name

src/commands/config/flowConfig.mli

@@ -142,6 +142,8 @@ val node_resolver_allow_root_relative : config -> bool
 
 val node_resolver_dirnames : config -> string list
 
+val node_resolver_root_relative_dirnames : config -> string list
+
 val required_version : config -> string option
 
 val recursion_limit : config -> int

src/common/options.ml

@@ -101,6 +101,7 @@ type t = {
   opt_modules_are_use_strict: bool;
   opt_munge_underscores: bool;
   opt_node_resolver_allow_root_relative: bool;
+  opt_node_resolver_root_relative_dirnames: string list;
   opt_no_saved_state: bool;
   opt_profile: bool;
   opt_quiet: bool;
@@ -203,6 +204,8 @@ let no_saved_state opts = opts.opt_no_saved_state
 
 let node_resolver_allow_root_relative opts = opts.opt_node_resolver_allow_root_relative
 
+let node_resolver_root_relative_dirnames opts = opts.opt_node_resolver_root_relative_dirnames
+
 let recursion_limit opts = opts.opt_recursion_limit
 
 let root opts = opts.opt_root

src/services/inference/module/module_js.ml

@@ -370,7 +370,18 @@ module Node = struct
         [
           lazy
             ( if Options.node_resolver_allow_root_relative options then
-              resolve_relative ~options ~reader loc ?resolution_acc root_str import_str
+              lazy_seq
+                ( Options.node_resolver_root_relative_dirnames options
+                |> Core_list.map ~f:(fun root_relative_dirname ->
+                       lazy
+                         (let root_str =
+                            if root_relative_dirname = "" then
+                              root_str
+                            else
+                              Filename.concat root_str root_relative_dirname
+                          in
+                          resolve_relative ~options ~reader loc ?resolution_acc root_str import_str))
+                )
             else
               None );
           lazy

tests/config_module_system_node_root_relative_dirnames/.flowconfig

@@ -0,0 +1,4 @@
+[options]
+module.system.node.allow_root_relative=true
+module.system.node.root_relative_dirname=first
+module.system.node.root_relative_dirname=second

tests/config_module_system_node_root_relative_dirnames/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "user_code" = "user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/config_module_system_node_root_relative_dirnames.exp

@@ -0,0 +1,156 @@
+Error ----------------------------------------------------------------------------------------------------- test.js:16:2
+
+Cannot cast `ambiguous` to empty because string literal `first_user_code` [1] is incompatible with empty [2].
+
+   test.js:16:2
+   16| (ambiguous: empty)
+        ^^^^^^^^^
+
+References:
+   first/ambiguous.js:3:14
+    3| const value: "first_user_code" = "first_user_code";
+                    ^^^^^^^^^^^^^^^^^ [1]
+   test.js:16:13
+   16| (ambiguous: empty)
+                   ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:19:2
+
+Cannot cast `sub_ambiguous` to empty because string literal `first_user_code` [1] is incompatible with empty [2].
+
+   test.js:19:2
+   19| (sub_ambiguous: empty)
+        ^^^^^^^^^^^^^
+
+References:
+   first/subdir/ambiguous.js:3:14
+    3| const value: "first_user_code" = "first_user_code";
+                    ^^^^^^^^^^^^^^^^^ [1]
+   test.js:19:17
+   19| (sub_ambiguous: empty)
+                       ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:23:2
+
+Cannot cast `user_code` to empty because string literal `first_user_code` [1] is incompatible with empty [2].
+
+   test.js:23:2
+   23| (user_code: empty)
+        ^^^^^^^^^
+
+References:
+   first/user_code.js:3:14
+    3| const value: "first_user_code" = "first_user_code";
+                    ^^^^^^^^^^^^^^^^^ [1]
+   test.js:23:13
+   23| (user_code: empty)
+                   ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:26:2
+
+Cannot cast `sub_user_code` to empty because string literal `first_user_code` [1] is incompatible with empty [2].
+
+   test.js:26:2
+   26| (sub_user_code: empty)
+        ^^^^^^^^^^^^^
+
+References:
+   first/subdir/user_code.js:3:14
+    3| const value: "first_user_code" = "first_user_code";
+                    ^^^^^^^^^^^^^^^^^ [1]
+   test.js:26:17
+   26| (sub_user_code: empty)
+                       ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:30:2
+
+Cannot cast `second_only_user_code` to empty because string literal `second_only_user_code` [1] is incompatible with
+empty [2].
+
+   test.js:30:2
+   30| (second_only_user_code: empty)
+        ^^^^^^^^^^^^^^^^^^^^^
+
+References:
+   second/second_only_user_code.js:3:14
+    3| const value: "second_only_user_code" = "second_only_user_code";
+                    ^^^^^^^^^^^^^^^^^^^^^^^ [1]
+   test.js:30:25
+   30| (second_only_user_code: empty)
+                               ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:33:2
+
+Cannot cast `sub_second_only_user_code` to empty because string literal `second_only_user_code` [1] is incompatible with
+empty [2].
+
+   test.js:33:2
+   33| (sub_second_only_user_code: empty)
+        ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+References:
+   second/subdir/second_only_user_code.js:3:14
+    3| const value: "second_only_user_code" = "second_only_user_code";
+                    ^^^^^^^^^^^^^^^^^^^^^^^ [1]
+   test.js:33:29
+   33| (sub_second_only_user_code: empty)
+                                   ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:37:2
+
+Cannot cast `node_code` to empty because string literal `node_code` [1] is incompatible with empty [2].
+
+   test.js:37:2
+   37| (node_code: empty)
+        ^^^^^^^^^
+
+References:
+   node_modules/node_code.js:3:14
+    3| const value: "node_code" = "node_code";
+                    ^^^^^^^^^^^ [1]
+   test.js:37:13
+   37| (node_code: empty)
+                   ^^^^^ [2]
+
+
+Error ----------------------------------------------------------------------------------------------------- test.js:40:2
+
+Cannot cast `sub_node_code` to empty because string literal `node_code` [1] is incompatible with empty [2].
+
+   test.js:40:2
+   40| (sub_node_code: empty)
+        ^^^^^^^^^^^^^
+
+References:
+   node_modules/subdir/node_code.js:3:14
+    3| const value: "node_code" = "node_code";
+                    ^^^^^^^^^^^ [1]
+   test.js:40:17
+   40| (sub_node_code: empty)
+                       ^^^^^ [2]
+
+
+Error ---------------------------------------------------------------------------------------------------- test.js:43:25
+
+Cannot resolve module `nonexistent`.
+
+   43| import nonexistent from 'nonexistent'
+                               ^^^^^^^^^^^^^
+
+
+Error ---------------------------------------------------------------------------------------------------- test.js:44:29
+
+Cannot resolve module `subdir/nonexistent`.
+
+   44| import sub_nonexistent from 'subdir/nonexistent'
+                                   ^^^^^^^^^^^^^^^^^^^^
+
+
+
+Found 10 errors

tests/config_module_system_node_root_relative_dirnames/first/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "first_user_code" = "first_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/first/subdir/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "first_user_code" = "first_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/first/subdir/user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "first_user_code" = "first_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/first/user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "first_user_code" = "first_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_user_code" = "second_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/second_only_user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_only_user_code" = "second_only_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/subdir/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_user_code" = "second_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/subdir/second_only_user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_only_user_code" = "second_only_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/subdir/user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_user_code" = "second_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/second/user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "second_user_code" = "second_user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/subdir/ambiguous.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "user_code" = "user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/subdir/user_code.js

@@ -0,0 +1,4 @@
+// @flow
+
+const value: "user_code" = "user_code";
+export default value;

tests/config_module_system_node_root_relative_dirnames/test.js

@@ -0,0 +1,44 @@
+// @flow
+
+/**
+ * 1) All "ambiguous" code exists in first/, second/ and node_modules/.
+ *    first/ wins
+ * 2) All "user_code" code exists in first/ and second/
+ *    first/ wins
+ * 3) All "second_only" code exists only in second/
+ *    second/ wins
+ * 4) All "node_code" code exists in only node_modules/
+ *    node_modules/ wins
+ */
+
+// These exist in both user code and node_modules, but user code wins
+import ambiguous from 'ambiguous';
+(ambiguous: empty)
+
+import sub_ambiguous from 'subdir/ambiguous';
+(sub_ambiguous: empty)
+
+// These exist in only user code
+import user_code from 'user_code';
+(user_code: empty)
+
+import sub_user_code from 'subdir/user_code';
+(sub_user_code: empty)
+
+// These exist in only user code, and only in second/
+import second_only_user_code from 'second_only_user_code';
+(second_only_user_code: empty)
+
+import sub_second_only_user_code from 'subdir/second_only_user_code';
+(sub_second_only_user_code: empty)
+
+// These exist in only node code
+import node_code from 'node_code';
+(node_code: empty)
+
+import sub_node_code from 'subdir/node_code';
+(sub_node_code: empty)
+
+// These exist nowhere
+import nonexistent from 'nonexistent'
+import sub_nonexistent from 'subdir/nonexistent'