Perform coercion for query strings in parser module

lib/philomena/comments/query.ex

@@ -94,7 +94,6 @@ defmodule Philomena.Comments.Query do
 
   def compile(query_string, opts \\ []) do
     user = Keyword.get(opts, :user)
-    query_string = query_string || ""
 
     case user do
       nil ->

lib/philomena/filters/query.ex

@@ -35,7 +35,6 @@ defmodule Philomena.Filters.Query do
 
   def compile(query_string, opts \\ []) do
     user = Keyword.get(opts, :user)
-    query_string = query_string || ""
 
     case user do
       nil ->

lib/philomena/galleries/query.ex

@@ -15,8 +15,6 @@ defmodule Philomena.Galleries.Query do
   end
 
   def compile(query_string) do
-    query_string = query_string || ""
-
     fields()
     |> Parser.new()
     |> Parser.parse(query_string)

lib/philomena/images/query.ex

@@ -147,7 +147,6 @@ defmodule Philomena.Images.Query do
   def compile(query_string, opts \\ []) do
     user = Keyword.get(opts, :user)
     watch = Keyword.get(opts, :watch, false)
-    query_string = query_string || ""
 
     case user do
       nil ->

lib/philomena/posts/query.ex

@@ -92,7 +92,6 @@ defmodule Philomena.Posts.Query do
 
   def compile(query_string, opts \\ []) do
     user = Keyword.get(opts, :user)
-    query_string = query_string || ""
 
     case user do
       nil ->

lib/philomena/reports/query.ex

@@ -17,6 +17,6 @@ defmodule Philomena.Reports.Query do
   def compile(query_string) do
     fields()
     |> Parser.new()
-    |> Parser.parse(query_string || "", %{})
+    |> Parser.parse(query_string, %{})
   end
 end

lib/philomena/tags/query.ex

@@ -20,6 +20,6 @@ defmodule Philomena.Tags.Query do
   def compile(query_string) do
     fields()
     |> Parser.new()
-    |> Parser.parse(query_string || "")
+    |> Parser.parse(query_string)
   end
 end

lib/philomena_query/parse/parser.ex

@@ -184,18 +184,18 @@ defmodule PhilomenaQuery.Parse.Parser do
   @spec parse(t(), String.t(), context()) :: {:ok, query()} | {:error, String.t()}
   def parse(parser, input, context \\ nil)
 
-  # Empty search should emit a match_none.
-  def parse(_parser, "", _context) do
-    {:ok, %{match_none: %{}}}
-  end
-
   def parse(%Parser{} = parser, input, context) do
     parser = %{parser | __data__: context}
 
-    with {:ok, tokens, _1, _2, _3, _4} <- Lexer.lex(input),
+    with {:ok, input} <- coerce_string(input),
+         {:ok, tokens, _1, _2, _3, _4} <- Lexer.lex(input),
+         {:ok, tokens} <- convert_empty_token_list(tokens),
          {:ok, {tree, []}} <- search_top(parser, tokens) do
       {:ok, tree}
     else
+      {:error, :empty_query} ->
+        {:ok, %{match_none: %{}}}
+
       {:ok, {_tree, tokens}} ->
         {:error, "junk at end of expression: " <> debug_tokens(tokens)}
 
@@ -211,6 +211,13 @@ defmodule PhilomenaQuery.Parse.Parser do
     end
   end
 
+  defp coerce_string(term) when is_binary(term), do: {:ok, term}
+  defp coerce_string(nil), do: {:ok, ""}
+  defp coerce_string(_), do: {:error, "search query is not a string"}
+
+  defp convert_empty_token_list([]), do: {:error, :empty_query}
+  defp convert_empty_token_list(tokens), do: {:ok, tokens}
+
   defp debug_tokens(tokens) do
     Enum.map_join(tokens, fn {_k, v} -> v end)
   end

lib/philomena_web/controllers/api/json/search/gallery_controller.ex

@@ -7,7 +7,7 @@ defmodule PhilomenaWeb.Api.Json.Search.GalleryController do
   import Ecto.Query
 
   def index(conn, params) do
-    case Query.compile(params["q"] || "") do
+    case Query.compile(params["q"]) do
       {:ok, query} ->
         galleries =
           Gallery

lib/philomena_web/controllers/api/json/search/tag_controller.ex

@@ -7,7 +7,7 @@ defmodule PhilomenaWeb.Api.Json.Search.TagController do
   import Ecto.Query
 
   def index(conn, params) do
-    case Query.compile(params["q"] || "") do
+    case Query.compile(params["q"]) do
       {:ok, query} ->
         tags =
           Tag