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Max Schaefer
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Merge pull request #519 from esben-semmle/js/nullish-coalescing-extractor-and-ql
JS: nullish coalescing support in extractor and QL
2 parents a1772a9 + 2d7f09d commit 588defd

19 files changed

Lines changed: 2790 additions & 9 deletions

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‎change-notes/1.20/extractor-javascript.md‎

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[[ condition: enterprise-only ]]
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# Improvements to JavaScript analysis
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> NOTES
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>
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> Please describe your changes in terms that are suitable for
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> customers to read. These notes will have only minor tidying up
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> before they are published as part of the release notes.
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>
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> This file is written for lgtm users and should contain *only*
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> notes about changes that affect lgtm enterprise users. Add
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> any other customer-facing changes to the `studio-java.md`
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> file.
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>
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## General improvements
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## Changes to code extraction
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* The extractor now supports [Nullish Coalescing](https://github.com/tc39/proposal-nullish-coalescing) expressions.

‎javascript/extractor/src/com/semmle/jcorn/Parser.java‎

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@@ -508,8 +508,12 @@ private Token readToken_dot() {
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private Token readToken_question() { // '?'
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int next = charAt(this.pos + 1);
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int next2 = charAt(this.pos + 2);
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if (this.options.esnext() && next == '.' && !('0' <= next2 && next2 <= '9')) // '?.', but not '?.X' where X is a digit
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return this.finishOp(TokenType.questiondot, 2);
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if (this.options.esnext()) {
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if (next == '.' && !('0' <= next2 && next2 <= '9')) // '?.', but not '?.X' where X is a digit
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return this.finishOp(TokenType.questiondot, 2);
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if (next == '?') // '??'
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return this.finishOp(TokenType.questionquestion, 2);
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}
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return this.finishOp(TokenType.question, 1);
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}
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‎javascript/extractor/src/com/semmle/jcorn/TokenType.java‎

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@@ -123,6 +123,7 @@ public void updateContext(Parser parser, TokenType prevType) {
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}
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},
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prefix = new TokenType(new Properties("prefix").beforeExpr().prefix().startsExpr()),
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questionquestion = new TokenType(binop("??", 1)),
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logicalOR = new TokenType(binop("||", 1)),
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logicalAND = new TokenType(binop("&&", 2)),
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bitwiseOR = new TokenType(binop("|", 3)),

‎javascript/extractor/src/com/semmle/js/extractor/CFGExtractor.java‎

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@@ -331,9 +331,11 @@ public Node visit(MemberDefinition<?> nd, Void v) {
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return nd.getKey().accept(this, v);
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}
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// for binary operators, the operands come first (but not for LogicalExpression, see above)
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// for binary operators, the operands come first (but not for short-circuiting expressions), see above)
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@Override
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public Node visit(BinaryExpression nd, Void v) {
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if ("??".equals(nd.getOperator()))
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return nd;
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return nd.getLeft().accept(this, v);
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}
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@@ -1583,8 +1585,16 @@ protected void visitAssign(INode assgn, INode lhs, Expression rhs) {
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@Override
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public Void visit(BinaryExpression nd, SuccessorInfo i) {
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this.seq(nd.getLeft(), nd.getRight(), nd);
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succ(nd, i.getGuardedSuccessors(nd));
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if ("??".equals(nd.getOperator())) {
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// the nullish coalescing operator is short-circuiting, but we do not add guards for it
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succ(nd, First.of(nd.getLeft()));
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Object leftSucc = union(First.of(nd.getRight()), i.getAllSuccessors()); // short-circuiting happens with both truthy and falsy values
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visit(nd.getLeft(), leftSucc, null);
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nd.getRight().accept(this, i);
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} else {
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this.seq(nd.getLeft(), nd.getRight(), nd);
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succ(nd, i.getGuardedSuccessors(nd));
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}
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return null;
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}
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‎javascript/extractor/src/com/semmle/js/extractor/ExprKinds.java‎

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@@ -72,6 +72,7 @@ public class ExprKinds {
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binOpKinds.put("&=", 58);
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binOpKinds.put("**", 87);
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binOpKinds.put("**=", 88);
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binOpKinds.put("??", 107);
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}
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private static final Map<String, Integer> unOpKinds = new LinkedHashMap<String, Integer>();

‎javascript/extractor/src/com/semmle/js/extractor/Main.java‎

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@@ -41,7 +41,7 @@ public class Main {
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* such a way that it may produce different tuples for the same file under the same
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* {@link ExtractorConfig}.
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*/
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public static final String EXTRACTOR_VERSION = "2018-11-22_a";
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public static final String EXTRACTOR_VERSION = "2018-11-23";
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public static final Pattern NEWLINE = Pattern.compile("\n");
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‎javascript/extractor/tests/esnext/input/nullish-coalescing.js‎

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x1 ?? y1;
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x2 || y2 ?? z2;
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x3 ?? y3 || z3;
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x4 && y4 ?? z4;
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x5 ?? y5 && z5;

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