Wrapped try-with-resources resource declaration gets unnecessary added semicolon

[ZachCallear]

Prettier-Java 2.7.3

# Options (if any):
(no options)

Input:

  public static void formatTest() throws IOException {
    try (var object = new ByteArrayOutputStream()) {
      var test = 1;
    }
    try (
      var objectWithALongerNameThatCausesABreak = new ByteArrayOutputStream()
    ) {
      var test = 1;
    }
  }

Output:

  public static void formatTest() throws IOException {
    try (var object = new ByteArrayOutputStream()) {
      var test = 1;
    }
    try (
      var objectWithALongerNameThatCausesABreak = new ByteArrayOutputStream();
    ) {
      var test = 1;
    }
  }

Expected behavior:
The semicolon at the end of the resource declaration statement is unnecessary. The "Unnecessary semicolon" inspection in IDEA reports it as a Weak Warning, with no option to disable the inspection for just this particular case. The formatter should, at minimum, probably not add a semicolon in this context. Whether it ought to remove an existing one is more debatable.

[ZachCallear]

I've experimented and determined that this behavior (adding the semicolon) begins to occur in 2.7.1, as it does not occur in 2.6.8. I haven't bisected for the specific commit.

[ZachCallear]

I'm guessing it's caused by resources.push(ifBreak(";")); in packages/prettier-plugin-java/src/printers/blocks-and-statements.ts, in:

  resourceSpecification(path, print, options) {
    const resources = [call(path, print, "resourceList")];
    if (options.trailingComma !== "none") {
      resources.push(ifBreak(";"));
    }
    return indentInParentheses(resources);
  },

This was seemingly introduced in 6339feb.

[jtkiesel]

This was done purposefully. When the trailingComma option isn't set to none, prettier-plugin-java will place commas anywhere that Java allows one. The elements of a resource list are similar to an array, and in this specific instance Java allows a trailing semicolon, so we now treat it similarly.

The reason to include a trailing semicolon in this case is similar to the reason to include a trailing comma in multi-line arrays, which is to reduce the likelihood of having to modify a different line when adding or removing an element to the list. Without a trailing comma/semicolon, you may have to add/remove a comma/semicolon on a line other than the line you're modifying, which affects git blame, for example.

To disable this behavior, set trailingComma to none.

[ZachCallear]

That makes sense. Thank you for the explanation. I love comma-dangling, and I agree that the semicolon serves the same purpose as a comma in this context.

It might help to document this behavior somewhere, though, as Prettier's documentation doesn't mention semicolons in the description of that option, so others might end up confused, since very technically, the semicolon terminates a normal assignment statement in this context.

[jtkiesel]

After thinking about it more, I think you're right that while the dangling semicolon is similar in this case stylistically, it is a very different situation and not at all intuitively related to an option named trailingComma. Since this is a pretty rare case, I think I'll just revert the behavior back to what it was previously, where if the semicolon was already present, it is printed, and if it was absent, it is omitted. Later we could consider adding a javaTrailingSemicolon or something similar if we want to allow the enforcing of this, but since it's such a rare case, that probably isn't necessary.