opa fmt ... displaces comments

[mikol]

Expected Behavior

How exactly the comments are preserved is more art than science at this point. That said, the following seem like good guidelines:

A. Comments within a block should remain within the block (not appear outside of the block)
B. Block-starting comments (e.g., { # Begin) should be preserved as-is
C. Block-ending comments (e.g., } # End) should be preserved as-is

There will inevitably be cases that can’t feasibly be accommodated because we’re talking about re-commenting code after it has been formatted, which may leave the formatted code in such a state that the original comments cannot be placed in any way that match the author’s original intent.

Given the following input, I expect formatted code to preserve comments more-or-less as suggested above.

# ------------------------------------------------------------------------------
# Header

package comments

rule {
  object.b == empty
} # End rule

# Middle

fn(x) = 1 { # Else 0
  # A
  data.foo # B
  # C
} else = 2 { # Else 1
  # D
  data.bar # E
  # F
} else = 3 { # Else 2
  # G
  data.biz # H
  # I
} # End else

array = [ # M
 2, 3, 5, 7
 # N
] # End array

# Footer
# ------------------------------------------------------------------------------

Actual Behavior

# ------------------------------------------------------------------------------
# Header

package comments

rule {
	object.b == empty
}

# End rule

# Middle

fn(x) = 1 { # Else 0
	# A
	data.foo # B
	# C
} # Else 1

else = 2 {
	# D
	data.bar # E
}

# F
else = 3 { # Else 2
	# G
	data.biz # H
}

# I
# End else

array = [2, 3, 5, 7] # M

# N
# End array
# Footer
# ------------------------------------------------------------------------------

Consider:

rule {
	object.b == empty
}

# End rule

I would have expected # End rule to remain at the end of the closing curly brace as } # End rule.

Then:

fn(x) = 1 { # Else 0
	# A
	data.foo # B
	# C
} # Else 1

else = 2 {
	# D
	data.bar # E
}

# F
else = 3 { # Else 2
	# G
	data.biz # H
}

# I
# End else

The first rule body is formatted as I would expect. Each else isn’t as expected. For example. I would expect # Else 1 to appear after the else block’s opening curly braces (same as # Else 0 and # Else 2). There’s some ambiguity, however, since I (personally) would have expected the else rule heads to appear on the same line as the previous closing curly (i.e., } else = 2 { # Else 1), but that might be a subjective style consideration.

#F and #I should appear within the open and closing curly braces of the else bodies.

As for:

array = [2, 3, 5, 7] # M

# N
# End array

It’s unclear what to expect in this case since the formatting rule for the array/set rewrites the original to be 100% inline.

Steps to Reproduce the Problem

Run opa fmt ... on the input.

[tsandall]

Thanks for filing this @mikol. I think it should be possible to at least make the formatting around else more consistent. For example:

• # Else 0 and # Else 2 are in the right position but # Else 1 is not.
• # C is in the right position but # F and # I are not.

If the fix requires the position of the closing brace characters it might be more problematic since we don't have end positions.

[stale]

This issue has been automatically marked as inactive because it has not had any activity in the last 30 days.

[anderseknert]

Closing in favor of #4508, where we'll try to compile all ideas for the next iteration of opa fmt (and where this is included).