Denotes dupe keys in package.json to textual feedback instead of erro…

…ring out (#156)

lua/package-info/parser.lua

@@ -4,19 +4,50 @@ local clean_version = require("package-info.helpers.clean_version")
 
 local M = {}
 
+local function createKeySet(tbl)
+    local keySet = {}
+    for key in pairs(tbl) do
+        keySet[key] = true
+    end
+    return keySet
+end
+
+local function intersectKeySets(set1, set2)
+    local intersection = {}
+    for key in pairs(set1) do
+        if set2[key] then
+            intersection[key] = true
+        end
+    end
+    return intersection
+end
+
+local function intersect(t1, t2)
+    local s1 = createKeySet(t1)
+    local s2 = createKeySet(t2)
+    return intersectKeySets(s1, s2)
+end
+
 M.parse_buffer = function()
     local buffer_lines = vim.api.nvim_buf_get_lines(state.buffer.id, 0, -1, false)
     local buffer_json_value = json_parser.decode(table.concat(buffer_lines))
 
+    local intersection = intersect(buffer_json_value["devDependencies"] or {}, buffer_json_value["dependencies"] or {})
     local all_dependencies_json =
-        vim.tbl_extend("error", {}, buffer_json_value["devDependencies"] or {}, buffer_json_value["dependencies"] or {})
+        vim.tbl_extend("force", {}, buffer_json_value["devDependencies"] or {}, buffer_json_value["dependencies"] or {})
 
     local installed_dependencies = {}
 
     for name, version in pairs(all_dependencies_json) do
-        installed_dependencies[name] = {
-            current = clean_version(version),
-        }
+        if intersection[name] ~= nil then
+            installed_dependencies[name] = {
+                current = "[ERROR] DEPENDENCY IS DUPLICATED",
+            }
+        else
+            installed_dependencies[name] = {
+                current = clean_version(version),
+            }
+        end
     end
 
     state.buffer.lines = buffer_lines