Make it impossible to have a project rule without visitors

phantom-type-tests/No_Project_Rule_Without_Visitors.elm

@@ -0,0 +1,12 @@
+module No_Project_Rule_Without_Visitors exposing (rule)
+
+{-| We want to forbid having project rules without any visitors.
+-}
+
+import Review.Rule as Rule exposing (Rule)
+
+
+rule : Rule
+rule =
+    Rule.newProjectRuleSchema "No_Project_Rule_Without_Visitors" ()
+        |> Rule.fromProjectRuleSchema

phantom-type-tests/No_Project_Rule_Without_Visitors.txt

@@ -0,0 +1,31 @@
+-- TYPE MISMATCH ------------------------ ./No_Project_Rule_Without_Visitors.elm
+
+This function cannot handle the argument sent through the (|>) pipe:
+
+11|     Rule.newProjectRuleSchema "No_Project_Rule_Without_Visitors" ()
+12|         |> Rule.fromProjectRuleSchema
+               ^^^^^^^^^^^^^^^^^^^^^^^^^^
+The argument is:
+
+    Rule.ProjectRuleSchema
+        ()
+        moduleContext
+        { canAddModuleVisitor : (), withModuleContext : Rule.NotNeeded }
+
+But (|>) is piping it to a function that expects:
+
+    Rule.ProjectRuleSchema
+        ()
+        moduleContext
+        { a
+            | canAddModuleVisitor : ()
+            , hasAtLeastOneVisitor : ()
+            , withModuleContext : Rule.NotNeeded
+        }
+
+Hint: Seems like a record field typo. Maybe hasAtLeastOneVisitor should be
+canAddModuleVisitor?
+
+Hint: Can more type annotations be added? Type annotations always help me give
+more specific messages, and I think they could help a lot in this case!
+

phantom-type-tests/No_WithModuleVisitor_After_WithModuleContext.txt

@@ -13,17 +13,24 @@ This function cannot handle the argument sent through the (|>) pipe:
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 The argument is:
 
-    Rule.ProjectRuleSchema () () { withModuleContext : Rule.NotNeeded }
+    Rule.ProjectRuleSchema
+        ()
+        ()
+        { hasAtLeastOneVisitor : (), withModuleContext : Rule.NotNeeded }
 
 But (|>) is piping it to a function that expects:
 
     Rule.ProjectRuleSchema
         ()
         ()
-        { a | canAddModuleVisitor : (), withModuleContext : Rule.NotNeeded }
+        { a
+            | canAddModuleVisitor : ()
+            , hasAtLeastOneVisitor : ()
+            , withModuleContext : Rule.NotNeeded
+        }
 
 Hint: Seems like a record field typo. Maybe canAddModuleVisitor should be
-withModuleContext?
+hasAtLeastOneVisitor?
 
 Hint: Can more type annotations be added? Type annotations always help me give
 more specific messages, and I think they could help a lot in this case!

phantom-type-tests/No_WithModuleVisitor_Without_WithModuleContext.txt

@@ -18,5 +18,15 @@ But (|>) is piping it to a function that expects:
     Rule.ProjectRuleSchema
         ()
         ()
-        { canAddModuleVisitor : (), withModuleContext : Rule.NotNeeded }
+        { a
+            | canAddModuleVisitor : ()
+            , hasAtLeastOneVisitor : ()
+            , withModuleContext : Rule.NotNeeded
+        }
+
+Hint: Seems like a record field typo. Maybe hasAtLeastOneVisitor should be
+canAddModuleVisitor?
+
+Hint: Can more type annotations be added? Type annotations always help me give
+more specific messages, and I think they could help a lot in this case!
 

phantom-type-tests/WithModuleContext_AtMostOnce.txt

@@ -17,19 +17,24 @@ This function cannot handle the argument sent through the (|>) pipe:
 
 The argument is:
 
-    Rule.ProjectRuleSchema () () { withModuleContext : Rule.NotNeeded }
+    Rule.ProjectRuleSchema
+        ()
+        ()
+        { hasAtLeastOneVisitor : (), withModuleContext : Rule.NotNeeded }
 
 But (|>) is piping it to a function that expects:
 
     Rule.ProjectRuleSchema
         ()
         ()
-        { schemaState
-            | canAddModuleVisitor : (), withModuleContext : Rule.Required
+        { a
+            | canAddModuleVisitor : ()
+            , hasAtLeastOneVisitor : ()
+            , withModuleContext : Rule.Required
         }
 
 Hint: Seems like a record field typo. Maybe canAddModuleVisitor should be
-withModuleContext?
+hasAtLeastOneVisitor?
 
 Hint: Can more type annotations be added? Type annotations always help me give
 more specific messages, and I think they could help a lot in this case!

phantom-type-tests/run-phantom-tests.js

@@ -21,3 +21,5 @@ elmFiles.forEach(elmFile => {
     }
   }
 });
+
+console.log('No problems with phantom types!');

src/Review/Rule.elm

@@ -947,7 +947,7 @@ newProjectRuleSchema name_ initialProjectContext =
 
 {-| Create a [`Rule`](#Rule) from a configured [`ProjectRuleSchema`](#ProjectRuleSchema).
 -}
-fromProjectRuleSchema : ProjectRuleSchema projectContext moduleContext { schemaState | withModuleContext : NotNeeded } -> Rule
+fromProjectRuleSchema : ProjectRuleSchema projectContext moduleContext { schemaState | withModuleContext : NotNeeded, hasAtLeastOneVisitor : () } -> Rule
 fromProjectRuleSchema (ProjectRuleSchema schema) =
     Rule schema.name
         Exceptions.init
@@ -1007,7 +1007,7 @@ withModuleContext :
     , foldProjectContexts : projectContext -> projectContext -> projectContext
     }
     -> ProjectRuleSchema projectContext moduleContext { schemaState | canAddModuleVisitor : (), withModuleContext : Required }
-    -> ProjectRuleSchema projectContext moduleContext { schemaState | withModuleContext : NotNeeded }
+    -> ProjectRuleSchema projectContext moduleContext { schemaState | hasAtLeastOneVisitor : (), withModuleContext : NotNeeded }
 withModuleContext moduleContext (ProjectRuleSchema schema) =
     let
         visitors : List (ModuleRuleSchema {} moduleContext -> ModuleRuleSchema { hasAtLeastOneVisitor : () } moduleContext)
@@ -1035,7 +1035,7 @@ module is evaluated.
 withElmJsonProjectVisitor :
     (Maybe { elmJsonKey : ElmJsonKey, project : Elm.Project.Project } -> projectContext -> ( List Error, projectContext ))
     -> ProjectRuleSchema projectContext moduleContext schemaState
-    -> ProjectRuleSchema projectContext moduleContext schemaState
+    -> ProjectRuleSchema projectContext moduleContext { schemaState | hasAtLeastOneVisitor : () }
 withElmJsonProjectVisitor visitor (ProjectRuleSchema schema) =
     ProjectRuleSchema { schema | elmJsonVisitors = visitor :: schema.elmJsonVisitors }
 
@@ -1051,7 +1051,7 @@ module is evaluated.
 withReadmeProjectVisitor :
     (Maybe { readmeKey : ReadmeKey, content : String } -> projectContext -> ( List Error, projectContext ))
     -> ProjectRuleSchema projectContext moduleContext schemaState
-    -> ProjectRuleSchema projectContext moduleContext schemaState
+    -> ProjectRuleSchema projectContext moduleContext { schemaState | hasAtLeastOneVisitor : () }
 withReadmeProjectVisitor visitor (ProjectRuleSchema schema) =
     ProjectRuleSchema { schema | readmeVisitors = visitor :: schema.readmeVisitors }
 
@@ -1066,7 +1066,7 @@ module is evaluated.
 withDependenciesProjectVisitor :
     (Dict String Review.Project.Dependency.Dependency -> projectContext -> ( List Error, projectContext ))
     -> ProjectRuleSchema projectContext moduleContext schemaState
-    -> ProjectRuleSchema projectContext moduleContext schemaState
+    -> ProjectRuleSchema projectContext moduleContext { schemaState | hasAtLeastOneVisitor : () }
 withDependenciesProjectVisitor visitor (ProjectRuleSchema schema) =
     ProjectRuleSchema { schema | dependenciesVisitors = visitor :: schema.dependenciesVisitors }
 

src/Scope2.elm

@@ -168,7 +168,7 @@ emptyScope =
 
 addProjectVisitors :
     Rule.ProjectRuleSchema { projectContext | scope : ProjectContext } { moduleContext | scope : ModuleContext } { schemaState | canAddModuleVisitor : () }
-    -> Rule.ProjectRuleSchema { projectContext | scope : ProjectContext } { moduleContext | scope : ModuleContext } { schemaState | canAddModuleVisitor : (), withModuleContext : Rule.Required }
+    -> Rule.ProjectRuleSchema { projectContext | scope : ProjectContext } { moduleContext | scope : ModuleContext } { schemaState | canAddModuleVisitor : (), hasAtLeastOneVisitor : (), withModuleContext : Rule.Required }
 addProjectVisitors schema =
     schema
         |> Rule.withContextFromImportedModules