syntax: errors and/or breaks code when arrays have keys that contain pound signs or variables #1285

I'm using shfmt 3.12.0.

The following is valid Bash, and when used in the context of a larger script (like this), it works as expected:

#!/usr/bin/env bash

# ...

for ((I=0; I < ARGS[COMMAND,#]; I++)); do
  ENTR_ARGS+=("${ARGS[COMMAND,$I]}")
done

In the above code, the ARGS array has a key named COMMAND,# and also keys named COMMAND,1, COMMAND,2, etc. It might look a little unusual, but the code is valid, and that pattern is used by docopts.

When shfmt is run on that code, the following error occurs:

ef:4:28: , must be followed by an expression

If that issue is fixed, by quoting the name of the key, like this:

#!/usr/bin/env bash

# ...

for ((I=0; I < ARGS['COMMAND,#']; I++)); do
  ENTR_ARGS+=("${ARGS[COMMAND,$I]}")
done

...and shfmt is run on the file again, then the code is formatted to the following, which does not work:

#!/usr/bin/env bash

# ...

for ((I = 0; I < ARGS['COMMAND,#']; I++)); do
  ENTR_ARGS+=("${ARGS[COMMAND, I]}")
done

In the second-to-last line, the line beginning with ENTR_ARGS+=, notice that a space was inserted after the comma and the dollar sign was removed from the I variable.

As before, the workaround appears to be quoting the name of the key. The nested double quotes look weird, but it works as expected, so I assume it's valid Bash:

#!/usr/bin/env bash

# ...

for ((I = 0; I < ARGS['COMMAND,#']; I++)); do
  ENTR_ARGS+=("${ARGS["COMMAND,$I"]}")
done