Do not report an error for doc attributes file invalid in erlang module

Summary:
The `erlang` module for OTP 27 has a doc attribute

```
-doc {file,"../../doc/src/erlang_system_info.md"}.
```

The referenced file is not included in all erlang binary packages, so silence the error if it is not found.

Also, some errors emitted by `elp_epp` were referring to `epp`, not `elp_epp`, so were not being formatted correctly.

Reviewed By: RobinMorisset

Differential Revision: D60166779

fbshipit-source-id: 5c2f77bd458396cb826df4c2c6352ac94f636fe8

crates/ide/src/diagnostics.rs

@@ -2274,4 +2274,35 @@ baz(1)->4.
             "#,
         );
     }
+
+    #[test]
+    fn file_not_found_doc_attribute() {
+        check_diagnostics(
+            r#"
+            //- erlang_service
+            //- native
+            //- /my_app/src/a_file.erl
+              -module(a_file).
+
+              -doc {file,"../../doc/src/info.md"}.
+             %%          ^^^^^^^^^^^^^^^^^^^^^^^ error: can't find doc file "../../doc/src/info.md"
+
+            "#,
+        );
+    }
+
+    #[test]
+    fn file_not_found_doc_attribute_ignored_in_erlang() {
+        check_diagnostics(
+            r#"
+            //- erlang_service
+            //- native
+            //- /my_app/src/erlang.erl
+              -module(erlang).
+
+              -doc {file,"../../doc/src/info.md"}.
+
+            "#,
+        );
+    }
 }

erlang_service/src/elp_epp.erl

@@ -1017,10 +1017,10 @@ scan_filedoc(
     scan_filedoc_content(DocFilename, Dot, DocType, From, St);
 scan_filedoc([{'(', _}, {'{', _}, {atom, _, file} | _] = Toks, DocType, From, St) ->
     T = find_mismatch(['(', '{', atom, ',', string, '}', ')', dot], Toks, DocType),
-    epp_reply(From, {error, {loc(T), epp, {bad, DocType}}}),
+    epp_reply(From, {error, {loc(T), elp_epp, {bad, DocType}}}),
     wait_req_scan(St);
 scan_filedoc([{'(', _}, {'{', _}, T | _], DocType, From, St) ->
-    epp_reply(From, {error, {loc(T), epp, {DocType, invalid, file}}}),
+    epp_reply(From, {error, {loc(T), elp_epp, {DocType, invalid, file}}}),
     wait_req_scan(St);
 scan_filedoc(
     [
@@ -1038,18 +1038,18 @@ scan_filedoc(
     scan_filedoc_content(DocFilename, Dot, DocType, From, St);
 scan_filedoc([{'{', _}, {atom, _, file} | _] = Toks, {atom, _, DocType}, From, St) ->
     T = find_mismatch(['{', {atom, file}, ',', string, '}', dot], Toks, DocType),
-    epp_reply(From, {error, {loc(T), epp, {bad, DocType}}}),
+    epp_reply(From, {error, {loc(T), elp_epp, {bad, DocType}}}),
     wait_req_scan(St);
 scan_filedoc([{'{', _}, T | _], {atom, _, DocType}, From, St) ->
-    epp_reply(From, {error, {loc(T), epp, {DocType, invalid, file}}}),
+    epp_reply(From, {error, {loc(T), elp_epp, {DocType, invalid, file}}}),
     wait_req_scan(St).
 
 %% Reads the content of the file and rewrites the AST as if
 %% the content had been written in-place.
 scan_filedoc_content(
-    {string, _A, DocFilename},
+    {string, DocLoc, DocFilename},
     Dot,
-    {atom, DocLoc, Doc},
+    {atom, _DocLoc, Doc},
     From,
     #epp{name = CurrentFilename} = St
 ) ->
@@ -1085,11 +1085,24 @@ scan_filedoc_content(
                     wait_req_scan(St);
                 {error, _} ->
                     ok = file:close(NewF),
-                    epp_reply(From, {error, {DocLoc, epp, {Doc, file, DocFilename}}}),
+                    epp_reply(From, {error, {DocLoc, elp_epp, {Doc, file, DocFilename}}}),
                     wait_req_scan(St)
             end;
         {error, _} ->
-            epp_reply(From, {error, {DocLoc, epp, {Doc, file, DocFilename}}}),
+            %% We are unable to load the specified include file for the doc contents.
+            %% The `erlang.erl` OTP file tries to include files not shipped. So skip them.
+            case maps:get('MODULE', St#epp.macs) of
+               {none, [{atom, _, erlang}]} ->
+                    Loc = DocLoc,
+                    epp_reply(
+                    From,
+                    {ok,
+                    [{'-', Loc}, {atom, Loc, Doc}] ++
+                        [{string, Loc, unicode:characters_to_list("**skipping**")}, {dot, Loc}]}
+                    );
+                _ ->
+                  epp_reply(From, {error, {DocLoc, elp_epp, {Doc, file, DocFilename}}})
+            end,
             wait_req_scan(St)
     end.
 
@@ -1525,9 +1538,9 @@ scan_if([{'(', _} | _] = Toks, If, From, St) ->
                     {_, erl_parse, _} ->
                         {error, Error0};
                     {error, ErrL, What} ->
-                        {error, {ErrL, epp, What}};
+                        {error, {ErrL, elp_epp, What}};
                     _ ->
-                        {error, {loc(If), epp, Error0}}
+                        {error, {loc(If), elp_epp, Error0}}
                 end,
             epp_reply(From, Error),
             wait_req_skip(St, ['if'])