fix: modify diff calculation to handle end-of-file newlines better (#35)

3 files changed, 18 insertions, 15 deletions

diff --git a/tests/fuzzer_spec.lua b/tests/fuzzer_spec.lua
index 81c032f..639cfa9 100644
--- a/tests/fuzzer_spec.lua
+++ b/tests/fuzzer_spec.lua
@@ -1,6 +1,7 @@
 require("plenary.async").tests.add_to_env()
 local test_util = require("tests.test_util")
 local conform = require("conform")
+local log = require("conform.log")
 local runner = require("conform.runner")
 
 describe("fuzzer", function()
@@ -25,12 +26,6 @@ describe("fuzzer", function()
     vim.api.nvim_buf_set_lines(bufnr, 0, -1, true, buf_content)
     vim.bo[bufnr].modified = false
     runner.apply_format(0, buf_content, expected, nil, false)
-    -- We expect the last newline to be effectively "swallowed" by the formatter
-    -- because vim will use that as the EOL at the end of the file. The exception is that we always
-    -- expect at least one line in the output
-    if #expected > 1 and expected[#expected] == "" then
-      table.remove(expected)
-    end
     assert.are.same(expected, vim.api.nvim_buf_get_lines(0, 0, -1, false))
   end
 
@@ -95,6 +90,10 @@ describe("fuzzer", function()
     for _ = 1, num_lines do
       table.remove(lines, idx)
     end
+    -- vim will never let the lines be empty. An empty file has a single blank line.
+    if #lines == 0 then
+      table.insert(lines, "")
+    end
   end
 
   local function make_edits(lines)
@@ -112,8 +111,10 @@ describe("fuzzer", function()
   end
 
   it("formats correctly", function()
+    -- log.level = vim.log.levels.TRACE
     for i = 1, 50000 do
       math.randomseed(i)
+      log.info("Fuzz testing with seed %d", i)
       local content = make_file(20)
       local formatted = make_edits(content)
       run_formatter(content, formatted)
diff --git a/tests/runner_spec.lua b/tests/runner_spec.lua
index 8807d2d..10ea075 100644
--- a/tests/runner_spec.lua
+++ b/tests/runner_spec.lua
@@ -125,12 +125,6 @@ describe("runner", function()
       local expected_lines = vim.split(expected, "\n", { plain = true })
       test_util.set_formatter_output(expected_lines)
       conform.format(vim.tbl_extend("force", opts or {}, { formatters = { "test" }, quiet = true }))
-      -- We expect the last newline to be effectively "swallowed" by the formatter
-      -- because vim will use that as the EOL at the end of the file. The exception is that we always
-      -- expect at least one line in the output
-      if #expected_lines > 1 and expected_lines[#expected_lines] == "" then
-        table.remove(expected_lines)
-      end
       return expected_lines
     end
 
@@ -193,11 +187,14 @@ print("a")
       run_formatter_test("\nfoo", "\nhello\nfoo")
       run_formatter_test("hello", "hello\n")
       run_formatter_test("hello", "hello\n\n")
-      run_formatter_test("hello", "hello\n")
-      -- This should generate no changes to the buffer
-      assert.falsy(vim.bo.modified)
       run_formatter_test("hello\n", "hello")
       run_formatter_test("hello\n ", "hello")
+
+      -- These should generate no changes to the buffer
+      run_formatter_test("hello\n", "hello\n")
+      assert.falsy(vim.bo.modified)
+      run_formatter_test("hello", "hello")
+      assert.falsy(vim.bo.modified)
     end)
 
     it("does not change output if formatter fails", function()
diff --git a/tests/test_util.lua b/tests/test_util.lua
index a225aec..cded23a 100644
--- a/tests/test_util.lua
+++ b/tests/test_util.lua
@@ -1,5 +1,6 @@
 require("plenary.async").tests.add_to_env()
 local conform = require("conform")
+local log = require("conform.log")
 local M = {}
 
 local OUTPUT_FILE = "tests/fake_formatter_output"
@@ -21,6 +22,8 @@ M.reset_editor = function()
   if vim.fn.filereadable(OUTPUT_FILE) == 1 then
     vim.fn.delete(OUTPUT_FILE)
   end
+  log.level = vim.log.levels.ERROR
+  log.set_handler(print)
 end
 
 ---@param lines string[]
@@ -28,6 +31,8 @@ M.set_formatter_output = function(lines)
   local content = table.concat(lines, "\n")
   local fd = assert(vim.loop.fs_open(OUTPUT_FILE, "w", 420)) -- 0644
   vim.loop.fs_write(fd, content)
+  -- Make sure we add the final newline
+  vim.loop.fs_write(fd, "\n")
   vim.loop.fs_close(fd)
 end