github.com/mem/u-root@v2.0.1-0.20181004165302-9b18b4636a33+incompatible/cmds/elvish/edit/highlight/emitter.go (about)

     1  package highlight
     2  
     3  import (
     4  	"strings"
     5  
     6  	"github.com/u-root/u-root/cmds/elvish/edit/ui"
     7  	"github.com/u-root/u-root/cmds/elvish/eval"
     8  	"github.com/u-root/u-root/cmds/elvish/parse"
     9  )
    10  
    11  type Emitter struct {
    12  	GoodFormHead func(string) bool
    13  	AddStyling   func(begin, end int, style string)
    14  }
    15  
    16  func (e *Emitter) EmitAll(n parse.Node) {
    17  	switch n := n.(type) {
    18  	case *parse.Form:
    19  		e.form(n)
    20  	case *parse.Primary:
    21  		e.primary(n)
    22  	case *parse.Sep:
    23  		e.sep(n)
    24  	}
    25  	for _, child := range n.Children() {
    26  		e.EmitAll(child)
    27  	}
    28  }
    29  
    30  func (e *Emitter) form(n *parse.Form) {
    31  	for _, an := range n.Assignments {
    32  		if an.Left != nil && an.Left.Head != nil {
    33  			v := an.Left.Head
    34  			e.AddStyling(v.Begin(), v.End(), styleForGoodVariable.String())
    35  		}
    36  	}
    37  	for _, cn := range n.Vars {
    38  		if len(cn.Indexings) > 0 && cn.Indexings[0].Head != nil {
    39  			v := cn.Indexings[0].Head
    40  			e.AddStyling(v.Begin(), v.End(), styleForGoodVariable.String())
    41  		}
    42  	}
    43  	if n.Head != nil {
    44  		e.formHead(n.Head)
    45  		// Special forms
    46  		switch n.Head.SourceText() {
    47  		case "if":
    48  			for i := 2; i < len(n.Args); i += 2 {
    49  				a := n.Args[i]
    50  				argText := a.SourceText()
    51  				if argText == "elif" || argText == "else" {
    52  					e.AddStyling(a.Begin(), a.End(), styleForSep[argText])
    53  				}
    54  			}
    55  		case "for":
    56  			if len(n.Args) >= 1 && len(n.Args[0].Indexings) > 0 {
    57  				v := n.Args[0].Indexings[0].Head
    58  				e.AddStyling(v.Begin(), v.End(), styleForGoodVariable.String())
    59  			}
    60  			if len(n.Args) >= 4 && n.Args[3].SourceText() == "else" {
    61  				a := n.Args[3]
    62  				e.AddStyling(a.Begin(), a.End(), styleForSep["else"])
    63  			}
    64  		case "try":
    65  			i := 1
    66  			highlightKeyword := func(name string) bool {
    67  				if i >= len(n.Args) {
    68  					return false
    69  				}
    70  				a := n.Args[i]
    71  				if a.SourceText() != name {
    72  					return false
    73  				}
    74  				e.AddStyling(a.Begin(), a.End(), styleForSep[name])
    75  				return true
    76  			}
    77  			if highlightKeyword("except") {
    78  				if i+1 < len(n.Args) && len(n.Args[i+1].Indexings) > 0 {
    79  					v := n.Args[i+1].Indexings[0]
    80  					e.AddStyling(v.Begin(), v.End(), styleForGoodVariable.String())
    81  				}
    82  				i += 3
    83  			}
    84  			if highlightKeyword("else") {
    85  				i += 2
    86  			}
    87  			highlightKeyword("finally")
    88  		}
    89  		// TODO(xiaq): Handle other special forms.
    90  	}
    91  }
    92  
    93  func (e *Emitter) formHead(n *parse.Compound) {
    94  	head, err := eval.PurelyEvalCompound(n)
    95  	st := ui.Styles{}
    96  	if err == nil {
    97  		if e.GoodFormHead(head) {
    98  			st = styleForGoodCommand
    99  		} else {
   100  			st = styleForBadCommand
   101  		}
   102  	} else if err != eval.ErrImpure {
   103  		st = styleForBadCommand
   104  	}
   105  	if len(st) > 0 {
   106  		e.AddStyling(n.Begin(), n.End(), st.String())
   107  	}
   108  }
   109  
   110  func (e *Emitter) primary(n *parse.Primary) {
   111  	e.AddStyling(n.Begin(), n.End(), styleForPrimary[n.Type].String())
   112  }
   113  
   114  func (e *Emitter) sep(n *parse.Sep) {
   115  	septext := n.SourceText()
   116  	switch {
   117  	case strings.TrimSpace(septext) == "":
   118  		// Don't do anything. Whitespaces don't get any styling.
   119  	case strings.HasPrefix(septext, "#"):
   120  		// Comment.
   121  		e.AddStyling(n.Begin(), n.End(), styleForComment.String())
   122  	default:
   123  		e.AddStyling(n.Begin(), n.End(), styleForSep[septext])
   124  	}
   125  }