implement late constant-folding for && || ??

evanw · evanw · commit 8f1faf7d4a9e · 2024-05-24T14:39:41.000-04:00
diff --git a/internal/bundler_tests/snapshots/snapshots_dce.txt b/internal/bundler_tests/snapshots/snapshots_dce.txt
@@ -291,9 +291,9 @@ console.log([
   7,
   5
 ], [
-  3 /* a */ && 6 /* b */,
-  3 /* a */ || 6 /* b */,
-  3 /* a */ ?? 6 /* b */
+  6 /* b */,
+  3 /* a */,
+  3 /* a */
 ]);
 
 ---------- /out/const-entry.js ----------
@@ -329,9 +329,9 @@ console.log([
   7,
   5
 ], [
-  3 && 6,
-  3 || 6,
-  3 ?? 6
+  6,
+  3,
+  3
 ]);
 
 ---------- /out/nested-entry.js ----------
@@ -359,9 +359,9 @@ console.log([
   !1,
   !0
 ], [
-  "foo" /* a */ && "bar" /* b */,
-  "foo" /* a */ || "bar" /* b */,
-  "foo" /* a */ ?? "bar" /* b */
+  "bar" /* b */,
+  "foo" /* a */,
+  "foo" /* a */
 ]);
 
 ---------- /out/const-entry.js ----------
diff --git a/internal/js_ast/js_ast_helpers.go b/internal/js_ast/js_ast_helpers.go
@@ -1208,6 +1208,11 @@ func ShouldFoldBinaryOperatorWhenMinifying(binary *EBinary) bool {
 			resultLen := approximatePrintedIntCharCount(float64(ToUint32(left) >> (ToUint32(right) & 31)))
 			return resultLen <= leftLen+3+rightLen
 		}
+
+	case BinOpLogicalAnd, BinOpLogicalOr, BinOpNullishCoalescing:
+		if IsPrimitiveLiteral(binary.Left.Data) {
+			return true
+		}
 	}
 	return false
 }
@@ -1326,6 +1331,33 @@ func FoldBinaryOperator(loc logger.Loc, e *EBinary) Expr {
 		if left, right, ok := extractStringValues(e.Left, e.Right); ok {
 			return Expr{Loc: loc, Data: &EBoolean{Value: stringCompareUCS2(left, right) != 0}}
 		}
+
+	case BinOpLogicalAnd:
+		if boolean, sideEffects, ok := ToBooleanWithSideEffects(e.Left.Data); ok {
+			if !boolean {
+				return e.Left
+			} else if sideEffects == NoSideEffects {
+				return e.Right
+			}
+		}
+
+	case BinOpLogicalOr:
+		if boolean, sideEffects, ok := ToBooleanWithSideEffects(e.Left.Data); ok {
+			if boolean {
+				return e.Left
+			} else if sideEffects == NoSideEffects {
+				return e.Right
+			}
+		}
+
+	case BinOpNullishCoalescing:
+		if isNullOrUndefined, sideEffects, ok := ToNullOrUndefinedWithSideEffects(e.Left.Data); ok {
+			if !isNullOrUndefined {
+				return e.Left
+			} else if sideEffects == NoSideEffects {
+				return e.Right
+			}
+		}
 	}
 
 	return Expr{}
