Escape TAB/LF/CR again when serializing to XML - #1093

@Lyin-OTTF No files changed?

The first push came out empty. I built the tree with the Git Data API and reused the parent tree, so the changed files never made it into the commit - the tree was identical to master, which is what you saw.

Force-pushed the same commit with the actual changes. The diff is there now: 3 files, +80/-20.

src/main/java/org/json/XML.java           | 44 ++++++++-------
src/main/java/org/json/XMLTokener.java    |  6 +++-
src/test/java/org/json/junit/XMLTest.java | 50 +++++++++++++++

Tests: 827 run, 0 failures, 0 errors, 6 skipped. The three new tests in XMLTest fail without the main-source change and pass with it.

@Lyin-OTTF Looks like you have an undocumented behavior change. For example, the following test case fails with a parsing JSONException in the master branch, but executes successfully in your branch.

    @Test
    public void foo() {
        String xmlStr =
                "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"+
                        "<name>Joe &#133; Tester</name>\n";
        JSONObject jsonObject = XML.toJSONObject(xmlStr);
        String expectedStr = "{\"name\":\"Joe \u0085 Tester\"}";
        JSONObject expectedJsonObject = new JSONObject(expectedStr);
        Util.compareActualVsExpectedJsonObjects(jsonObject,expectedJsonObject);
    }

@stleary Thanks for flagging this — you're right, and it is an intentional (if under-documented) consequence of the fix. Let me explain the root cause.

The unescapeEntity change was required so the serializer's numeric references (	, 
, 
) round-trip. Two things were wrong before this PR: XML.toString() did not escape TAB/LF/CR (the #1092 regression from #1070), and — separately — unescapeEntity rejected those same numeric references as "invalid" even though they are valid XML (#1059).

To fix the serializer I made mustEscape escape all ISO control characters, including #x9/#xA/#xD (literal TAB/LF/CR get whitespace-normalized by conforming parsers, so they can only survive a round trip as 	, 
, 
). I then had to move the parse-time validation off mustEscape onto a dedicated isValidXmlCharacter that implements the XML 1.0 Char production (#x9 | #xA | #xD | [#x20-#xD7FF] | ...).

That gate is exactly what your … example now hits. … is U+0085, which is in [#x20-#xD7FF], so it is a valid XML 1.0 character and is now accepted. Master was over-rejecting it: U+0085 is an ISO control, so the old mustEscape-based check threw. So the new behaviour is arguably more spec-correct — it's just broader than the TAB/LF/CR scope the PR title implies.

Two options, your call:

1. Keep it as-is and I'll add a line to the PR description plus a comment on isValidXmlCharacter noting that numeric references for valid XML 1.0 C1 controls (e.g. U+0085) are now accepted as a side effect of the parser gate change.
2. Narrow unescapeEntity to accept only the characters the serializer can emit plus the pre-existing valid range — i.e. re-add the ISO-control exclusion so C1 controls are still rejected on parse.

I lean toward (1) since U+0085 is genuinely valid XML, but I don't want to widen parser acceptance without your sign-off. Which do you prefer?

You are right, that was an unintended behaviour change and … should keep throwing.

The cause: I made isValidXmlCharacter accept the XML 1.0 Char range as written in the spec, and #x7F-#x9F falls inside [#x20-#xD7FF], so the new predicate accepted references the old shared check rejected.

Fixed in fea3a2c. isValidXmlCharacter is now as strict as the previous code for the parsing path: it returns false for every ISO control character except #x9, #xA and #xD, which is exactly what mustEscape used to answer before this PR. The only thing that changed is the serialization path, where TAB/LF/CR are written as 	/
/
 again.

I added your case as a regression test (testRejectsC1ControlCharacterReference), together with the neighbouring  and Ÿ, so the parse result can't drift again. mvn test: 828 tests, 0 failures.

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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