Move tuple wrapping for eqwalizer_fixmes to fixme.rs

Summary:
This stack aims at extracting ELP metadata (such as `elp:ignore` annotations) in the same way Eqwalizer does, and to leverage the metadata to suppress diagnostics (instead of using a separate implementation). This also enables detection of un-necessary ignore statements.

Before being able to do so, a few refactorings are required.

This first change simply moves EETF conversion details to the `fixmes_eetf` function.

Reviewed By: alanz

Differential Revision: D54536341

fbshipit-source-id: 348e513ac3a6948064a9cdfa1f328d0a42c5300e

crates/ide_db/src/erl_ast.rs

@@ -148,12 +148,7 @@ fn module_ast(
 fn elp_metadata(db: &dyn ErlAstDatabase, file_id: FileId) -> eetf::Term {
     let line_index = db.file_line_index(file_id);
     let file_text = db.file_text(file_id);
-    let fixmes = fixmes::fixmes_eetf(&line_index, &file_text);
-    // Erlang proplist: [{eqwalizer_fixmes, [Fixme1, Fixme2....]}]
-    eetf::List::from(vec![
-        eetf::Tuple::from(vec![eetf::Atom::from("eqwalizer_fixmes").into(), fixmes]).into(),
-    ])
-    .into()
+    fixmes::fixmes_eetf(&line_index, &file_text)
 }
 
 pub fn files_from_bytes(bytes: &[u8]) -> Vec<String> {

crates/ide_db/src/fixmes.rs

@@ -50,7 +50,15 @@ impl From<Fixme> for eetf::Term {
 pub fn fixmes_eetf(line_index: &LineIndex, file_text: &str) -> eetf::Term {
     let fixmes = collect_fixmes(line_index, file_text);
     let fixmes: Vec<eetf::Term> = fixmes.into_iter().map(|f| f.into()).collect();
-    eetf::List::from(fixmes).into()
+    // Erlang proplist: [{eqwalizer_fixmes, [Fixme1, Fixme2....]}]
+    eetf::List::from(vec![
+        eetf::Tuple::from(vec![
+            eetf::Atom::from("eqwalizer_fixmes").into(),
+            eetf::List::from(fixmes).into(),
+        ])
+        .into(),
+    ])
+    .into()
 }
 
 fn collect_fixmes(line_index: &LineIndex, file_text: &str) -> Vec<Fixme> {