My own favourite approach would link ASI to layout/indentation,
and introduce warnings instead of breaking code:
1 if ASI kicks in, but indentation suggests statement continuation,
issue a warning
2 if ASI does not kick in, but indentation suggests new statement,
issue a warning
I did once try to implement this, by instrumenting esprima to
keep track of indents and ASI and other side-conditions, but
got somewhat distracted/disillusioned by the number of
special cases that kept popping up. Nevertheless, that sketch
is now available as a gist:
https://gist.github.com/2973296
Perhaps it inspires someone to do it right?-)
Claus
// ----------------- output
$ node basil.js sample.js
ASI at line 5(2) before indented line 6(8)
multiline VariableDeclaration 12(2), not indented: line 13(2)
multiline VariableDeclaration 21(2), not indented: line 22(2)
ASI at line 23(2) before indented line 24(11)
multiline IfStatement 33(2), not indented: line 34(2)
ASI at line 37(2) before indented line 38(4)
multiline ExpressionStatement 40(2), not indented: line 42(2)
multiline WhileStatement 44(2), not indented: line 45(2)-line 47(2)
// ----------------- sample.js
$ cat sample.js
// examples
function restricted_production() {
return //;
"hi"; // warn here
return //;
"hi"; // don't warn here
}
function newline_no_asi() {
var x = ["hi"] //;
[1]; // warn here
var y = ["hi"] //;
[1]; // don't warn here
}
function newline_error_asi(alp,ha) {
var a1 = "hi"+
"ho"; // don't warn here
var a2 = "hi"+
"ho"; // warn here
var b1 = "hi" //;
"ho"; // warn here
var b2 = "hi" //;
"ho"; // don't warn here
}
function continued_statements() {
if (condition) {
} else { // don't warn here
} // don't warn here
if (condition) f
() // warn here
if (condition) f
() // don't warn here
if (condition) return
"" // warn here
if (condition) return
"" // don't warn here
// don't warn here (comment/empty multiline) FIXME
while (condition) {
} // don't warn here
while (condition) f
() // warn here
function f() {
} // don't warn here
}
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