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|
package reader
import (
"bytes"
"strings"
"github.com/alecthomas/chroma/v2"
)
// Read and highlight some text using Chroma:
// https://github.com/alecthomas/chroma
//
// If lexer is nil no highlighting will be performed.
//
// Returns nil with no error if highlighting would be a no-op.
func Highlight(text string, style chroma.Style, formatter chroma.Formatter, lexer chroma.Lexer) (*string, error) {
if lexer == nil {
// No highlighter available for this file type
return nil, nil
}
// FIXME: Can we test for the lexer implementation class instead? That
// should be more resilient towards this arbitrary string changing if we
// upgrade Chroma at some point.
if lexer.Config().Name == "plaintext" {
// This highlighter doesn't provide any highlighting, but not doing
// anything at all is cheaper and simpler, so we do that.
return nil, nil
}
// NOTE: We used to do...
//
// lexer = chroma.Coalesce(lexer)
//
// ... here, but with Chroma 2.12.0 that resulted in this problem:
// https://github.com/walles/moor/issues/236#issuecomment-2282677792
//
// So let's not do that anymore.
iterator, err := lexer.Tokenise(nil, text)
if err != nil {
return nil, err
}
var stringBuffer bytes.Buffer
err = formatter.Format(&stringBuffer, &style, iterator)
if err != nil {
return nil, err
}
highlighted := stringBuffer.String()
// If buffer ends with SGR Reset ("<ESC>[0m"), remove it. Chroma sometimes
// (always?) puts one of those by itself on the last line, making us believe
// there is one line too many.
sgrReset := "\x1b[0m"
trimmed := strings.TrimSuffix(highlighted, sgrReset)
return &trimmed, nil
}
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