inconsistent formatting of multi-argument function calls when memberExpression.linePerExpression: true

[adrian-gierakowski]

Describe the bug

dprint-plugin-typescript version: 0.95.12

looks like there is a bug when formatting code inside anonymous functions

Input Code

const startingFrom = Mylib.map(DateTime.now, now => DateTime.startOf(now, "day"));

const func = () =>
  function() {
    const startingFrom = Mylib.map(DateTime.now, now => DateTime.startOf(now, "day"));
  }

Expected Output

const startingFrom = Mylib.map(
  DateTime.now,
  now => DateTime.startOf(now, "day"),
);

const func = () =>
  function() {
    const startingFrom = Mylib.map(
      DateTime.now,
      now => DateTime.startOf(now, "day"),
    );
  };

Actual Output

const startingFrom = Mylib.map(
  DateTime.now,
  now => DateTime.startOf(now, "day"),
);

const func = () =>
  function() {
    const startingFrom = Mylib.map(DateTime.now, now =>
      DateTime.startOf(now, "day"));
  };

[adrian-gierakowski]

I've added a test case to a branch on my fork:

22b978d

I've also added a flake.nix so anyone (on mac or linux) could reproduce it with a one-liner:

> nix build github:adrian-gierakowski/dprint-plugin-typescript/22b978decd44d3203e9cfbc01aaf1b564039cbb5
error: Cannot build '/nix/store/0ir3l61dz99qijqg29xs054w92g0yzsm-dprint-plugin-typescript-0.95.8.drv'.
       Reason: builder failed with exit code 101.
       Output paths:
         /nix/store/68z77z6pk6jkx8vxy1z6bxl8qpa0any7-dprint-plugin-typescript-0.95.8
       Last 25 log lines:
       >  const startingFrom = Mylib.map(
       >    DateTime.now,
       >    now => DateTime.startOf(now, "day"),
       >  );
       >  
       >  const func = () =>
       >    function() {
       > -    const startingFrom = Mylib.map(
       > -      DateTime.now,
       > -      now => DateTime.startOf(now, "day"),
       > -    );
       > +    const startingFrom = Mylib.map(DateTime.now, now =>
       > +      DateTime.startOf(now, "day"));
       >    };
       >
       > Test file: ./tests/specs/issues/issue753.txt
       >
       > failures:
       >     specs::issues::issue753
       >
       >
       > thread 'main' panicked at /build/cargo-vendor-dir/file_test_runner-0.5.1/src/runner.rs:201:5:
       > 1 failed of 647
       > note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
       > error: test failed, to rerun pass `--test specs`
       For full logs, run:
         nix log /nix/store/0ir3l61dz99qijqg29xs054w92g0yzsm-dprint-plugin-typescript-0.95.8.drv

[adrian-gierakowski]

looks like this is related to #686

[adrian-gierakowski]

Initially I thought that the behaviour in the nested case is a bug, but after playing around with it a bit more I am not sure what was the authors intention, since adding braces around the function body changes behaviour at the top level to consistent with the nested case:

Input Code

const startingFrom = Mylib.map(DateTime.now, now => { return DateTime.startOf(now, "day") });

const func = () =>
  function() {
    const startingFrom = Mylib.map(DateTime.now, now => { return DateTime.startOf(now, "day") });
  }

Actual Output

const startingFrom = Mylib.map(DateTime.now, now => {
  return DateTime.startOf(now, "day");
});

const func = () =>
  function() {
    const startingFrom = Mylib.map(DateTime.now, now => {
      return DateTime.startOf(now, "day");
    });
  }

adding the braces also fixes the issues reported in #686 (see this comment)

[adrian-gierakowski]

although looking at the following, it seems like keeping arrow function which has no brace around the body on a single line is the expected behaviour:

Input

const func = now =>
  DateTime.startOf(now, "day");

Output

const func = now => DateTime.startOf(now, "day");

while adding braces forces next line fromating:

const func = now => { return DateTime.startOf(now, "day");}

Output

const func = now => {
  return DateTime.startOf(now, "day");
};

so my conclusion is that I was correct to assume in my original post that the top level formatting is the expected one. This also suggests that #754 is a valid fix

[adrian-gierakowski]

@dsherret would be great to hear your thoughts about the intended behaviour

given that this formatting works at the top:

const startingFrom = Mylib.map(DateTime.now, now => {
  return DateTime.startOf(now, "day");
});

should the following also work:

const startingFrom = Mylib.map(DateTime.now, now => 
  DateTime.startOf(now, "day")
);

if the latter should be allowed (currently each argument is forced onto it's own line), then the fix would have to be different, since it most likely just hides the underlying problem instead of fixing the root cause