Configuration Language using parsetcl

CMcC 4Jun2010

Config.tcl uses parsetcl to parse, then regenerate (I hesitate to say 'compile', but that is in fact what it is) a Tcl-like little language for configuration.

The little language looks like section-name {section} where the section is a Tcl script whose command-part is the name of a section variable and whose single argument is its value.

Values may contain arbitrary commands and comments, and may refer to section-local variables, fully-namespace qualified variables and section-qualified variables.

In short, it looks a lot like a Windows .ini file, but has Tcl syntax. Yay! Enjoy!

Thank you, Lars H, for parsetcl, which made this possible.

A version of the parsetcl script may be found here: http://abel.math.umu.se/~lars/tcl/parsetcl.tcl

# Config.tcl - support tcl-like config files

if {[info exists argv0] && ($argv0 eq [info script])} {
    lappend auto_path ~/Desktop/Work/Wub/ [file dirname [info script]]
}

if {[catch {package require Debug}]} {
    #proc Debug.config {args} {}
    proc Debug.config {args} {puts stderr [email protected][uplevel subst $args]}
} else {
    Debug define config 10
}

package require parsetcl
package provide Config 1.0

namespace eval parsetcl {
    proc unparse {tree} {
        eval $tree
    }

    # Lr - literal raw
    proc Lr {interval text args} {
        return $text
    }

    # Lb - literal braced
    proc Lb {interval text args} {
        return \{$text\}
    }

    # Lb - literal quoted
    proc Lq {interval text args} {
        return \"$text\"
    }

    # Sb - backslash substitution
    proc Sb {interval text args} {
        return "\\$text"
    }

    # Sv - scalar variable substitution
    proc Sv {interval text args} {
        return "\$[eval [lindex $args 0]]"
    }

    # Sa - array variable substitution
    proc Sa {interval text args} {
        foreach a [lrange $args 1 end] {
            append result [eval $a]
        }
        return "\$[eval [lindex $args 0]]($result)"
    }

    # Sc - command substitution
    proc Sc {interval text args} {
        set cmd {}
        foreach a $args {
            lappend cmd [eval $a]
        }
        return "\[[join $cmd]\]"
    }

    # Mr - raw merge
    proc Mr {interval text args} {
        foreach a $args {
            append result [eval $a]
        }
        return $result
    }

    # Mq - quoted merge
    proc Mq {interval text args} {
        foreach a $args {
            append result [eval $a]
        }
        return \"$result\"
    }

    # Mb - braced merge
    proc Mb {interval text args} {
        foreach a $args {
            append result [eval $a]
        }
        return \{$result\}
    }

    # Cd - complete command sans {*}
    proc Cd {interval text args} {
        set cmd {}
        foreach a $args {
            lappend cmd [eval $a]
        }
        return [join $cmd]
    }

    # Cx - {*}-construct
    proc Cx {interval text args} {
        set c {}
        foreach a $args {
            lappend c [eval $a]
        }
        return \{*\}[join $c]
    }

    # Ce - complete commands with {*}-constructs
    proc Ce {interval text args} {
        set c {}
        foreach a $args {
            lappend c [eval $a]
        }
        return [join $c]
    }

    # Cp - command prefix in Ce node
    proc Cp {interval text args} {
        set c {}
        foreach a $args {
            lappend c [eval $a]
        }
        return [join $c]
    }

    # Cr - non-prefix range of command words in a Ce node
    proc Cr {interval text args} {
        set c {}
        foreach a $args {
            lappend c [eval $a]
        }
        return [join $c]
    }

    # Rs - script - each arg is a command
    proc Rs {interval text args} {
        set cmd {}
        foreach a $args {
            lappend cmd [eval $a]
        }
        return "\{\n[join $cmd \n]\n\}"
    }

    # Rx - parsed expr
    proc Rx {interval text args} {
        set cmd {}
        foreach a $args {
            lappend cmd [eval $a]
        }
        return "\{\n[join $cmd]\n\}"
    }

    namespace export -clear *
    namespace ensemble create -subcommands {}
}

oo::class create Config {
    method parse {script} {
        set parse [parsetcl simple_parse_script $script]
        #puts stderr "Parse: $parse"
        #puts stderr "Format: [parsetcl format_tree $parse { } {   }]"
        #puts stderr "UnParse: [parsetcl unparse $parse]"
        set rendered {}

        parsetcl walk_tree parse index Cd {
            # body
            #puts stderr "walk: [lindex $parse {*}$index]"
            set cmd [lindex $parse {*}$index]
            lassign $cmd . . . left right
            set ll [parsetcl unparse $left]
            if {![string match L* [lindex $left 0]]} {
                error "section name '$ll' must be a literal ($left)"
            }
            if {[llength $cmd] != 5} {
                error "section $ll must have one argument only"
            }

            # get body
            set body [parsetcl simple_parse_script [lindex [parsetcl unparse $right] 0]]
            set NS [info object namespace [self]]

            # perform variable rewrite
            parsetcl walk_tree body bi Sv {
                set s [lindex $body {*}$bi 3 2]
                if {![string match ::* $s] && [string match *::* $s]} {
                    # this is section-relative var - we need to make a fully qualified NS
                    set s "${NS}::_C::$s"
                    lset body {*}$bi 3 2 $s
                }
                #puts stderr "VAR: $s"
            }

            # perform script transformation
            set rb ""
            parsetcl walk_tree body bi Rs {} C.* {
                set bcmd [lindex $body {*}$bi]
                lassign $bcmd . . . bl br
                if {[llength $bi] == 1} {
                    set bll [parsetcl unparse $bl]
                    if {![string match L* [lindex $bl 0]]} {
                        error "section name '$bll' must be a literal ($bl)"
                    }
                    if {[llength $bcmd] != 5} {
                        error "section $bll must have one argument only"
                    }
                    set brl [parsetcl unparse $br]
                    #puts stderr "BCMD $bi: ($bl) ($br) '$brl'"
                    
                    lappend rb "variable $bll $brl"
                } elseif {[parsetcl unparse $bl] eq "expr"} {
                    #puts stderr "EXPR: ($br) -> ([parsetcl parse_semiwords [parsetcl unparse $br]])"
                }
            }
            
            lappend rendered "namespace eval $ll [list [join $rb \;]]"

        } C.* {
            error "Don't know how to handle [lindex $parse {*}$index]"
        }

        set rendered [join $rendered \;]
        #puts stderr "RENDERED: $rendered"
        namespace eval _C $rendered
        return $parse
    }

    method extract {} {
        set result {}
        foreach ns [namespace children _C] {
            foreach var [info vars ${ns}::*] {
                dict set result [namespace tail $ns] [namespace tail $var] [set $var]
            }
        }
        return $result
    }

    constructor {args} {
        Debug.config {Creating Config [self] $args}
        if {[llength $args]%2} {
            set cf [lindex $args end]
            set args [lrange $args 0 end-1]
            dict set args config $cf
        }
        variable config ""
        variable {*}$args
        catch {set args [dict merge [Site var? Config] $args]}        ;# allow .ini file to modify defaults
        my eval $config
    }
}

if {[info exists argv0] && ($argv0 eq [info script])} {
    Debug on config 10

    Config create config
    config parse {
        section {
            var val        ;# this is a variable
            var1 val1
            v1 2
            v2 [expr {$v1 ^ 2}]
        }
        sect1 {
            v1 [expr {$section::v1 ^ 10}]
            ap [list moop {*}$::auto_path]
        }
    }
    puts stderr "DICT: [config extract]"
}