@@ -9,37 +9,46 @@ const RE_BLANK = /^[ \t]*$/;
99 * line and it must end on a line of its own, with the closing delimiter on a
1010 * next line.
1111 *
12- * @param {Array<string> } strings
13- * @param {...any } values
14- * @returns string
12+ * @param strings
13+ * @param values
1514 */
16- export default function ftl ( strings , ...values ) {
15+ export default function ftl (
16+ strings : TemplateStringsArray ,
17+ ...values : Array < unknown >
18+ ) : string {
1719 let code = strings . reduce ( ( acc , cur ) => acc + values . shift ( ) + cur ) ;
1820 let lines = code . split ( "\n" ) ;
19- let [ first , commonIndent ] = [ lines . shift ( ) , lines . pop ( ) ] ;
2021
21- if ( ! RE_BLANK . test ( first ) ) {
22+ let first = lines . shift ( ) ;
23+ if ( first === undefined || ! RE_BLANK . test ( first ) ) {
2224 throw new RangeError ( "Content must start on a new line." ) ;
2325 }
24- if ( ! RE_BLANK . test ( commonIndent ) ) {
26+
27+ let commonIndent = lines . pop ( ) ;
28+ if ( commonIndent === undefined || ! RE_BLANK . test ( commonIndent ) ) {
2529 throw new RangeError ( "Closing delimiter must appear on a new line." ) ;
2630 }
2731
28- function dedent ( line , idx ) {
32+ let dedented = [ ] ;
33+ for ( let i = 0 ; i < lines . length ; i ++ ) {
34+ let line = lines [ i ] ;
2935 let lineIndent = line . slice ( 0 , commonIndent . length ) ;
3036 if ( lineIndent . length === 0 ) {
3137 // Empty blank lines are preserved even if technically they are not
3238 // indented at all. This also short-circuits the dedentation logic when
3339 // commonIndent.length is 0, i.e. when all indents should be kept.
34- return line ;
40+ dedented . push ( line ) ;
41+ continue ;
3542 }
43+
3644 if ( lineIndent !== commonIndent ) {
3745 // The indentation of the line must match commonIndent exacty.
38- throw new RangeError ( `Insufficient indentation in line ${ idx + 1 } ) ;
46+ throw new RangeError ( `Insufficient indentation in line ${ i + 1 } ) ;
3947 }
48+
4049 // Strip commonIndent.
41- return line . slice ( commonIndent . length ) ;
50+ dedented . push ( line . slice ( commonIndent . length ) ) ;
4251 }
4352
44- return lines . map ( dedent ) . join ( "\n" ) ;
53+ return dedented . join ( "\n" ) ;
4554}
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