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Ensure no double newlines in files generated by "mix new" #15711

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Merged
josevalim merged 2 commits into from
Aug 3, 2026
+15 −22
Merged

Ensure no double newlines in files generated by "mix new" #15711

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80984be
Ensure no double newlines in files generated by "mix new"
rhcarvalho Aug 2, 2026
f35592a
Enforce rules on every generated file
rhcarvalho Aug 2, 2026
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37 changes: 15 additions & 22 deletions lib/mix/test/mix/tasks/new_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,16 +16,8 @@ defmodule Mix.Tasks.NewTest do
assert file =~ "version: \"0.1.0\""
end)

assert_file("hello_world/README.md", fn file ->
assert file =~ "# HelloWorld\n"
assert String.ends_with?(file, "\n")
refute String.ends_with?(file, "\n\n")
end)

assert_file("hello_world/.gitignore", fn file ->
assert String.ends_with?(file, "\n")
refute String.ends_with?(file, "\n\n")
end)
assert_file("hello_world/README.md", ~r/# HelloWorld\n/)
assert_file("hello_world/.gitignore")

assert_file("hello_world/lib/hello_world.ex", ~r/defmodule HelloWorld do/)
assert_file("hello_world/test/test_helper.exs", ~r/ExUnit.start()/)
Expand Down Expand Up @@ -126,16 +118,8 @@ defmodule Mix.Tasks.NewTest do
assert file =~ "apps_path: \"apps\""
end)

assert_file("hello_world/README.md", fn file ->
assert file =~ "# HelloWorld\n"
assert String.ends_with?(file, "\n")
refute String.ends_with?(file, "\n\n")
end)

assert_file("hello_world/.gitignore", fn file ->
assert String.ends_with?(file, "\n")
refute String.ends_with?(file, "\n\n")
end)
assert_file("hello_world/README.md", ~r/# HelloWorld\n/)
assert_file("hello_world/.gitignore")

assert_received {:mix_shell, :info, ["* creating mix.exs"]}

Expand Down Expand Up @@ -260,6 +244,15 @@ defmodule Mix.Tasks.NewTest do

defp assert_file(file) do
assert File.regular?(file), "Expected #{file} to exist, but does not"
content = File.read!(file)

# \S\n\z matches non-whitespace followed by a single newline at EOF
assert content == "" or content =~ ~r/\S\n\z/,
"Expected #{file} to end with a single trailing newline"

refute content =~ "\n\n\n", "Expected #{file} to not contain consecutive blank lines"

content
end

defp assert_file(file, match) do
Expand All @@ -268,8 +261,8 @@ defmodule Mix.Tasks.NewTest do
assert_file(file, &assert(&1 =~ match))

is_function(match, 1) ->
assert_file(file)
match.(File.read!(file))
content = assert_file(file)
match.(content)
end
end
end
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