reversible-preproc-cli

reversible-preproc-cli

Outline

reversible-preproc-cli is a command line interface on top of the npm core module reversible-preproc.

The preproc defines are supplied as a file input, or on the command line.
This differs from, for example, C, where the defines are inscribed in the file to be processed. The defines uses a Javascript style format allowing structured properties and values. E.g.,

{
    DEBUG: 2,
    select : 1,
    configs : [{
        A: 1, B: 2 
    }, {
        A: 2, B: 3 
    }]
}

The file to processed of course contains conditional statements (conditioned on the defines).
These conditional statements may be written in either of two styles:

• Psuedo Javascript ... (which doesn't use eval)
• Real javascript functions ... (which do use eval)

The Psuedo Javascript is briefer and more natural, but the Real Javascript is almighty.

For more details about the defines and the conditional statements, see the documentation for reversible-preproc on npm or github.

The "reversible" moniker indicates that it is suitable for lightweight switching back and forth between configuations (e.g., in-place). The deactivated regions are marked with annotated comments (//!!) enabling the preprocessor to remove them for a different configuration. Repeated applications of the same defines are idempotent.

Regexp is not used. Neither is all text searched. Only lines beginning with comment marks (e.g. //), are further processed as potential processing command lines. This makes processing relatively fast.

The rest of this document describes the CLI arguments.

CLI arguments

• -i --infile The file to be transformed. If omitted stdin will be used.

• -o --outfile The file to which to write the transformed data. If omitted stdout will be used.

• -f --deffile The file containing the JSON variable properties.

• -l --defline To pass the JSON defines inline. Due to the need to escape quotations marks this option is only usefule for simple cases.

• -t --testout Instead of outputting the transformed input, the output contains one line for conditional statement with the form: <T or F> <the conditional statement>

NOTE: Only one, and exactly one, of the '--deffile' and '--defline' options can/must be used.