Fix nil bug

Author: dglsparsons

AGENTS.md

@@ -83,6 +83,10 @@
 
 - For AI review panes, re-rendering existing split buffers during sync should preserve current window sizes; reusing `open()` without a layout-preserving option causes background refreshes to resize walkthrough splits.
 
+## Learned while hardening comment export against JSON nulls
+
+- `vim.json.decode()` turns JSON `null` into truthy `vim.NIL` userdata, so `comment.start_line or comment.line` is unsafe on decoded PR comment payloads. Normalize optional numeric fields with an explicit `type(value) == "number"` check before formatting ranges or applying suggestions.
+
 ## Project Overview
 
 `neo-reviewer` is a Neovim plugin for reviewing GitHub PRs. Hybrid architecture: Rust CLI for GitHub API/diff parsing, Lua plugin for UI.

lua/neo_reviewer/ui/comments.lua

@@ -104,15 +104,26 @@ local function build_line_spec(line, end_line)
     return tostring(line)
 end
 
+---@param value any
+---@return integer?
+local function coerce_integer(value)
+    -- vim.json.decode represents JSON null as vim.NIL, which is truthy userdata.
+    if type(value) == "number" then
+        return value
+    end
+    return nil
+end
+
 ---@param comment NRComment
 ---@return string?
 local function build_comment_location(comment)
-    if type(comment.path) ~= "string" or type(comment.line) ~= "number" then
+    local end_line = coerce_integer(comment.line)
+    if type(comment.path) ~= "string" or not end_line then
         return nil
     end
 
-    local start_line = comment.start_line or comment.line
-    local location = string.format("%s:%s", comment.path, build_line_spec(start_line, comment.line))
+    local start_line = coerce_integer(comment.start_line) or end_line
+    local location = string.format("%s:%s", comment.path, build_line_spec(start_line, end_line))
     local end_side = type(comment.side) == "string" and comment.side or nil
     local start_side = type(comment.start_side) == "string" and comment.start_side or end_side
 
@@ -144,9 +155,10 @@ local function format_local_comments_markdown()
     local has_comments = false
 
     for _, comment in ipairs(get_local_root_comments()) do
-        if type(comment.id) == "number" and type(comment.line) == "number" and type(comment.path) == "string" then
-            local start_line = comment.start_line or comment.line
-            table.insert(chunks, build_comment_heading(comment.id, comment.path, start_line, comment.line))
+        local end_line = coerce_integer(comment.line)
+        if type(comment.id) == "number" and end_line and type(comment.path) == "string" then
+            local start_line = coerce_integer(comment.start_line) or end_line
+            table.insert(chunks, build_comment_heading(comment.id, comment.path, start_line, end_line))
             table.insert(chunks, (comment.body or "") .. "\n\n")
             has_comments = true
         end
@@ -1229,8 +1241,8 @@ end
 ---@param comment NRComment
 ---@return string[]
 local function get_current_code_lines(source_bufnr, comment)
-    local start_line = comment.start_line or comment.line
-    local end_line = comment.line
+    local end_line = coerce_integer(comment.line)
+    local start_line = coerce_integer(comment.start_line) or end_line
     if not start_line or not end_line then
         return {}
     end
@@ -1314,8 +1326,8 @@ local function apply_suggestion(source_bufnr, suggestions, file_path)
     end
 
     local comment = sugg.comment
-    local start_line = comment.start_line or comment.line
-    local end_line = comment.line
+    local end_line = coerce_integer(comment.line)
+    local start_line = coerce_integer(comment.start_line) or end_line
 
     if not start_line or not end_line then
         vim.notify("Invalid suggestion line range", vim.log.levels.ERROR)

lua/tests/plenary/ui/comments_spec.lua

@@ -1057,6 +1057,52 @@ describe("neo_reviewer.ui.comments", function()
             )
         end)
 
+        it("ignores vim.NIL line metadata when formatting PR exports", function()
+            state.set_review({
+                pr = { number = 125, title = "Null metadata export", author = "author" },
+                files = {},
+                comments = {
+                    {
+                        id = 30,
+                        path = "src/nulls.lua",
+                        line = 12,
+                        start_line = vim.NIL,
+                        side = "RIGHT",
+                        start_side = vim.NIL,
+                        body = "Root comment with null range metadata",
+                        author = "reviewer",
+                        created_at = "2024-01-04T09:00:00Z",
+                        in_reply_to_id = vim.NIL,
+                    },
+                    {
+                        id = 31,
+                        path = "src/nulls.lua",
+                        line = 12,
+                        start_line = vim.NIL,
+                        side = "RIGHT",
+                        start_side = vim.NIL,
+                        body = "Reply with null range metadata",
+                        author = "author",
+                        created_at = "2024-01-04T10:00:00Z",
+                        in_reply_to_id = 30,
+                    },
+                },
+            })
+
+            local content = comments.format_comments_markdown()
+
+            assert.are.equal(
+                "# PR comments\n\n"
+                    .. "## Comment 30 (src/nulls.lua:12)\n"
+                    .. "@reviewer 2024-01-04 09:00\n\n"
+                    .. "Root comment with null range metadata\n\n"
+                    .. "### Reply 31 (src/nulls.lua:12)\n"
+                    .. "@author 2024-01-04 10:00\n\n"
+                    .. "Reply with null range metadata\n\n",
+                content
+            )
+        end)
+
         it("keeps orphan PR replies in the export", function()
             state.set_review({
                 pr = { number = 124, title = "Orphan reply export", author = "author" },