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DanielRosenwasserDanielRosenwasser
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Merge pull request microsoft#1571 from Arnavion/1570-template-strings
Don't emit an empty template head literal if there's a template span with a non-empty literal.
2 parents df4b3d2 + d07151f commit 7b11621

9 files changed

+103
-50
lines changed

‎src/compiler/emitter.ts‎

Lines changed: 39 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -2057,9 +2057,15 @@ module ts {
20572057
write("(");
20582058
}
20592059

2060-
emitLiteral(node.head);
2060+
var headEmitted = false;
2061+
if (shouldEmitTemplateHead()) {
2062+
emitLiteral(node.head);
2063+
headEmitted = true;
2064+
}
2065+
2066+
for (var i = 0; i < node.templateSpans.length; i++) {
2067+
var templateSpan = node.templateSpans[i];
20612068

2062-
forEach(node.templateSpans, templateSpan => {
20632069
// Check if the expression has operands and binds its operands less closely than binary '+'.
20642070
// If it does, we need to wrap the expression in parentheses. Otherwise, something like
20652071
// `abc${ 1 << 2 }`
@@ -2071,7 +2077,14 @@ module ts {
20712077
// "abc" + (1 << 2) + ""
20722078
var needsParens = templateSpan.expression.kind !== SyntaxKind.ParenthesizedExpression
20732079
&& comparePrecedenceToBinaryPlus(templateSpan.expression) !== Comparison.GreaterThan;
2074-
write(" + ");
2080+
2081+
if (i > 0 || headEmitted) {
2082+
// If this is the first span and the head was not emitted, then this templateSpan's
2083+
// expression will be the first to be emitted. Don't emit the preceding ' + ' in that
2084+
// case.
2085+
write(" + ");
2086+
}
2087+
20752088
emitParenthesized(templateSpan.expression, needsParens);
20762089
// Only emit if the literal is non-empty.
20772090
// The binary '+' operator is left-associative, so the first string concatenation
@@ -2081,12 +2094,34 @@ module ts {
20812094
write(" + ")
20822095
emitLiteral(templateSpan.literal);
20832096
}
2084-
});
2097+
}
20852098

20862099
if (emitOuterParens) {
20872100
write(")");
20882101
}
20892102

2103+
function shouldEmitTemplateHead() {
2104+
// If this expression has an empty head literal and the first template span has a non-empty
2105+
// literal, then emitting the empty head literal is not necessary.
2106+
// `${ foo } and ${ bar }`
2107+
// can be emitted as
2108+
// foo + " and " + bar
2109+
// This is because it is only required that one of the first two operands in the emit
2110+
// output must be a string literal, so that the other operand and all following operands
2111+
// are forced into strings.
2112+
//
2113+
// If the first template span has an empty literal, then the head must still be emitted.
2114+
// `${ foo }${ bar }`
2115+
// must still be emitted as
2116+
// "" + foo + bar
2117+
2118+
// There is always atleast one templateSpan in this code path, since
2119+
// NoSubstitutionTemplateLiterals are directly emitted via emitLiteral()
2120+
Debug.assert(node.templateSpans.length !== 0);
2121+
2122+
return node.head.text.length !== 0 || node.templateSpans[0].literal.text.length === 0;
2123+
}
2124+
20902125
function templateNeedsParens(template: TemplateExpression, parent: Expression) {
20912126
switch (parent.kind) {
20922127
case SyntaxKind.CallExpression:

‎tests/baselines/reference/templateStringBinaryOperations.js‎

Lines changed: 12 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -55,49 +55,49 @@ var l4 = 1 + `2${ 3 & 4 }5` + 6;
5555
//// [templateStringBinaryOperations.js]
5656
var a = 1 + ("" + 3);
5757
var b = 1 + ("2" + 3);
58-
var c = 1 + ("" + 3 + "4");
58+
var c = 1 + (3 + "4");
5959
var d = 1 + ("2" + 3 + "4");
6060
var e = ("" + 3) + 5;
6161
var f = ("2" + 3) + 5;
62-
var g = ("" + 3 + "4") + 5;
62+
var g = (3 + "4") + 5;
6363
var h = ("2" + 3 + "4") + 5;
6464
var i = 1 + ("" + 3) + 5;
6565
var j = 1 + ("2" + 3) + 5;
66-
var k = 1 + ("" + 3 + "4") + 5;
66+
var k = 1 + (3 + "4") + 5;
6767
var l = 1 + ("2" + 3 + "4") + 5;
6868
var a2 = 1 + ("" + (3 - 4));
6969
var b2 = 1 + ("2" + (3 - 4));
70-
var c2 = 1 + ("" + (3 - 4) + "5");
70+
var c2 = 1 + ((3 - 4) + "5");
7171
var d2 = 1 + ("2" + (3 - 4) + "5");
7272
var e2 = ("" + (3 - 4)) + 6;
7373
var f2 = ("2" + (3 - 4)) + 6;
74-
var g2 = ("" + (3 - 4) + "5") + 6;
74+
var g2 = ((3 - 4) + "5") + 6;
7575
var h2 = ("2" + (3 - 4) + "5") + 6;
7676
var i2 = 1 + ("" + (3 - 4)) + 6;
7777
var j2 = 1 + ("2" + (3 - 4)) + 6;
78-
var k2 = 1 + ("" + (3 - 4) + "5") + 6;
78+
var k2 = 1 + ((3 - 4) + "5") + 6;
7979
var l2 = 1 + ("2" + (3 - 4) + "5") + 6;
8080
var a3 = 1 + ("" + 3 * 4);
8181
var b3 = 1 + ("2" + 3 * 4);
82-
var c3 = 1 + ("" + 3 * 4 + "5");
82+
var c3 = 1 + (3 * 4 + "5");
8383
var d3 = 1 + ("2" + 3 * 4 + "5");
8484
var e3 = ("" + 3 * 4) + 6;
8585
var f3 = ("2" + 3 * 4) + 6;
86-
var g3 = ("" + 3 * 4 + "5") + 6;
86+
var g3 = (3 * 4 + "5") + 6;
8787
var h3 = ("2" + 3 * 4 + "5") + 6;
8888
var i3 = 1 + ("" + 3 * 4) + 6;
8989
var j3 = 1 + ("2" + 3 * 4) + 6;
90-
var k3 = 1 + ("" + 3 * 4 + "5") + 6;
90+
var k3 = 1 + (3 * 4 + "5") + 6;
9191
var l3 = 1 + ("2" + 3 * 4 + "5") + 6;
9292
var a4 = 1 + ("" + (3 & 4));
9393
var b4 = 1 + ("2" + (3 & 4));
94-
var c4 = 1 + ("" + (3 & 4) + "5");
94+
var c4 = 1 + ((3 & 4) + "5");
9595
var d4 = 1 + ("2" + (3 & 4) + "5");
9696
var e4 = ("" + (3 & 4)) + 6;
9797
var f4 = ("2" + (3 & 4)) + 6;
98-
var g4 = ("" + (3 & 4) + "5") + 6;
98+
var g4 = ((3 & 4) + "5") + 6;
9999
var h4 = ("2" + (3 & 4) + "5") + 6;
100100
var i4 = 1 + ("" + (3 & 4)) + 6;
101101
var j4 = 1 + ("2" + (3 & 4)) + 6;
102-
var k4 = 1 + ("" + (3 & 4) + "5") + 6;
102+
var k4 = 1 + ((3 & 4) + "5") + 6;
103103
var l4 = 1 + ("2" + (3 & 4) + "5") + 6;

‎tests/baselines/reference/templateStringBinaryOperationsInvalid.js‎

Lines changed: 24 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -111,97 +111,97 @@ var hc = `2${ 3 & 4 }5` & 6;
111111
//// [templateStringBinaryOperationsInvalid.js]
112112
var a = 1 - ("" + 3);
113113
var b = 1 - ("2" + 3);
114-
var c = 1 - ("" + 3 + "4");
114+
var c = 1 - (3 + "4");
115115
var d = 1 - ("2" + 3 + "4");
116116
var e = ("" + 3) - 5;
117117
var f = ("2" + 3) - 5;
118-
var g = ("" + 3 + "4") - 5;
118+
var g = (3 + "4") - 5;
119119
var h = ("2" + 3 + "4") - 5;
120120
var a2 = 1 * ("" + 3);
121121
var b2 = 1 * ("2" + 3);
122-
var c2 = 1 * ("" + 3 + "4");
122+
var c2 = 1 * (3 + "4");
123123
var d2 = 1 * ("2" + 3 + "4");
124124
var e2 = ("" + 3) * 5;
125125
var f2 = ("2" + 3) * 5;
126-
var g2 = ("" + 3 + "4") * 5;
126+
var g2 = (3 + "4") * 5;
127127
var h2 = ("2" + 3 + "4") * 5;
128128
var a3 = 1 & "" + 3;
129129
var b3 = 1 & "2" + 3;
130-
var c3 = 1 & "" + 3 + "4";
130+
var c3 = 1 & 3 + "4";
131131
var d3 = 1 & "2" + 3 + "4";
132132
var e3 = "" + 3 & 5;
133133
var f3 = "2" + 3 & 5;
134-
var g3 = "" + 3 + "4" & 5;
134+
var g3 = 3 + "4" & 5;
135135
var h3 = "2" + 3 + "4" & 5;
136136
var a4 = 1 - ("" + (3 - 4));
137137
var b4 = 1 - ("2" + (3 - 4));
138-
var c4 = 1 - ("" + (3 - 4) + "5");
138+
var c4 = 1 - ((3 - 4) + "5");
139139
var d4 = 1 - ("2" + (3 - 4) + "5");
140140
var e4 = ("" + (3 - 4)) - 6;
141141
var f4 = ("2" + (3 - 4)) - 6;
142-
var g4 = ("" + (3 - 4) + "5") - 6;
142+
var g4 = ((3 - 4) + "5") - 6;
143143
var h4 = ("2" + (3 - 4) + "5") - 6;
144144
var a5 = 1 - ("" + 3 * 4);
145145
var b5 = 1 - ("2" + 3 * 4);
146-
var c5 = 1 - ("" + 3 * 4 + "5");
146+
var c5 = 1 - (3 * 4 + "5");
147147
var d5 = 1 - ("2" + 3 * 4 + "5");
148148
var e5 = ("" + 3 * 4) - 6;
149149
var f5 = ("2" + 3 * 4) - 6;
150-
var g5 = ("" + 3 * 4 + "5") - 6;
150+
var g5 = (3 * 4 + "5") - 6;
151151
var h5 = ("2" + 3 * 4 + "5") - 6;
152152
var a6 = 1 - ("" + (3 & 4));
153153
var b6 = 1 - ("2" + (3 & 4));
154-
var c6 = 1 - ("" + (3 & 4) + "5");
154+
var c6 = 1 - ((3 & 4) + "5");
155155
var d6 = 1 - ("2" + (3 & 4) + "5");
156156
var e6 = ("" + (3 & 4)) - 6;
157157
var f6 = ("2" + (3 & 4)) - 6;
158-
var g6 = ("" + (3 & 4) + "5") - 6;
158+
var g6 = ((3 & 4) + "5") - 6;
159159
var h6 = ("2" + (3 & 4) + "5") - 6;
160160
var a7 = 1 * ("" + (3 - 4));
161161
var b7 = 1 * ("2" + (3 - 4));
162-
var c7 = 1 * ("" + (3 - 4) + "5");
162+
var c7 = 1 * ((3 - 4) + "5");
163163
var d7 = 1 * ("2" + (3 - 4) + "5");
164164
var e7 = ("" + (3 - 4)) * 6;
165165
var f7 = ("2" + (3 - 4)) * 6;
166-
var g7 = ("" + (3 - 4) + "5") * 6;
166+
var g7 = ((3 - 4) + "5") * 6;
167167
var h7 = ("2" + (3 - 4) + "5") * 6;
168168
var a8 = 1 * ("" + 3 * 4);
169169
var b8 = 1 * ("2" + 3 * 4);
170-
var c8 = 1 * ("" + 3 * 4 + "5");
170+
var c8 = 1 * (3 * 4 + "5");
171171
var d8 = 1 * ("2" + 3 * 4 + "5");
172172
var e8 = ("" + 3 * 4) * 6;
173173
var f8 = ("2" + 3 * 4) * 6;
174-
var g8 = ("" + 3 * 4 + "5") * 6;
174+
var g8 = (3 * 4 + "5") * 6;
175175
var h8 = ("2" + 3 * 4 + "5") * 6;
176176
var a9 = 1 * ("" + (3 & 4));
177177
var b9 = 1 * ("2" + (3 & 4));
178-
var c9 = 1 * ("" + (3 & 4) + "5");
178+
var c9 = 1 * ((3 & 4) + "5");
179179
var d9 = 1 * ("2" + (3 & 4) + "5");
180180
var e9 = ("" + (3 & 4)) * 6;
181181
var f9 = ("2" + (3 & 4)) * 6;
182-
var g9 = ("" + (3 & 4) + "5") * 6;
182+
var g9 = ((3 & 4) + "5") * 6;
183183
var h9 = ("2" + (3 & 4) + "5") * 6;
184184
var aa = 1 & "" + (3 - 4);
185185
var ba = 1 & "2" + (3 - 4);
186-
var ca = 1 & "" + (3 - 4) + "5";
186+
var ca = 1 & (3 - 4) + "5";
187187
var da = 1 & "2" + (3 - 4) + "5";
188188
var ea = "" + (3 - 4) & 6;
189189
var fa = "2" + (3 - 4) & 6;
190-
var ga = "" + (3 - 4) + "5" & 6;
190+
var ga = (3 - 4) + "5" & 6;
191191
var ha = "2" + (3 - 4) + "5" & 6;
192192
var ab = 1 & "" + 3 * 4;
193193
var bb = 1 & "2" + 3 * 4;
194-
var cb = 1 & "" + 3 * 4 + "5";
194+
var cb = 1 & 3 * 4 + "5";
195195
var db = 1 & "2" + 3 * 4 + "5";
196196
var eb = "" + 3 * 4 & 6;
197197
var fb = "2" + 3 * 4 & 6;
198-
var gb = "" + 3 * 4 + "5" & 6;
198+
var gb = 3 * 4 + "5" & 6;
199199
var hb = "2" + 3 * 4 + "5" & 6;
200200
var ac = 1 & "" + (3 & 4);
201201
var bc = 1 & "2" + (3 & 4);
202-
var cc = 1 & "" + (3 & 4) + "5";
202+
var cc = 1 & (3 & 4) + "5";
203203
var dc = 1 & "2" + (3 & 4) + "5";
204204
var ec = "" + (3 & 4) & 6;
205205
var fc = "2" + (3 & 4) & 6;
206-
var gc = "" + (3 & 4) + "5" & 6;
206+
var gc = (3 & 4) + "5" & 6;
207207
var hc = "2" + (3 & 4) + "5" & 6;

‎tests/baselines/reference/templateStringWithEmptyLiteralPortions.js‎

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -21,18 +21,22 @@ var j = `${ 0 }${ 0 }3`;
2121

2222
var k = `1${ 0 }${ 0 }3`;
2323

24-
var l = `1${ 0 }2${ 0 }3`;
24+
var l = `${ 0 }2${ 0 }3`;
25+
26+
var m = `1${ 0 }2${ 0 }3`;
27+
2528

2629
//// [templateStringWithEmptyLiteralPortions.js]
2730
var a = "";
2831
var b = "" + 0;
2932
var c = "1" + 0;
30-
var d = "" + 0 + "2";
33+
var d = 0 + "2";
3134
var e = "1" + 0 + "2";
3235
var f = "" + 0 + 0;
3336
var g = "1" + 0 + 0;
34-
var h = "" + 0 + "2" + 0;
37+
var h = 0 + "2" + 0;
3538
var i = "1" + 0 + "2" + 0;
3639
var j = "" + 0 + 0 + "3";
3740
var k = "1" + 0 + 0 + "3";
38-
var l = "1" + 0 + "2" + 0 + "3";
41+
var l = 0 + "2" + 0 + "3";
42+
var m = "1" + 0 + "2" + 0 + "3";

‎tests/baselines/reference/templateStringWithEmptyLiteralPortions.types‎

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -32,6 +32,9 @@ var j = `${ 0 }${ 0 }3`;
3232
var k = `1${ 0 }${ 0 }3`;
3333
>k : string
3434

35-
var l = `1${ 0 }2${ 0 }3`;
35+
var l = `${ 0 }2${ 0 }3`;
3636
>l : string
3737

38+
var m = `1${ 0 }2${ 0 }3`;
39+
>m : string
40+

‎tests/baselines/reference/templateStringWithEmptyLiteralPortionsES6.js‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -21,7 +21,10 @@ var j = `${ 0 }${ 0 }3`;
2121

2222
var k = `1${ 0 }${ 0 }3`;
2323

24-
var l = `1${ 0 }2${ 0 }3`;
24+
var l = `${ 0 }2${ 0 }3`;
25+
26+
var m = `1${ 0 }2${ 0 }3`;
27+
2528

2629
//// [templateStringWithEmptyLiteralPortionsES6.js]
2730
var a = ``;
@@ -35,4 +38,5 @@ var h = `${0}2${0}`;
3538
var i = `1${0}2${0}`;
3639
var j = `${0}${0}3`;
3740
var k = `1${0}${0}3`;
38-
var l = `1${0}2${0}3`;
41+
var l = `${0}2${0}3`;
42+
var m = `1${0}2${0}3`;

‎tests/baselines/reference/templateStringWithEmptyLiteralPortionsES6.types‎

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -32,6 +32,9 @@ var j = `${ 0 }${ 0 }3`;
3232
var k = `1${ 0 }${ 0 }3`;
3333
>k : string
3434

35-
var l = `1${ 0 }2${ 0 }3`;
35+
var l = `${ 0 }2${ 0 }3`;
3636
>l : string
3737

38+
var m = `1${ 0 }2${ 0 }3`;
39+
>m : string
40+

‎tests/cases/conformance/es6/templates/templateStringWithEmptyLiteralPortions.ts‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -20,4 +20,6 @@ var j = `${ 0 }${ 0 }3`;
2020

2121
var k = `1${ 0 }${ 0 }3`;
2222

23-
var l = `1${ 0 }2${ 0 }3`;
23+
var l = `${ 0 }2${ 0 }3`;
24+
25+
var m = `1${ 0 }2${ 0 }3`;

‎tests/cases/conformance/es6/templates/templateStringWithEmptyLiteralPortionsES6.ts‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -21,4 +21,6 @@ var j = `${ 0 }${ 0 }3`;
2121

2222
var k = `1${ 0 }${ 0 }3`;
2323

24-
var l = `1${ 0 }2${ 0 }3`;
24+
var l = `${ 0 }2${ 0 }3`;
25+
26+
var m = `1${ 0 }2${ 0 }3`;

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