Merge pull request #1257 from ispyisail/feature/pdf-reproducible

Add repeatable PDF export when SOURCE_DATE_EPOCH is set

tests/qttest/CMakeLists.txt

@@ -433,6 +433,19 @@ target_link_libraries(tst_potentialtextcarrier PRIVATE Qt::Test)
 target_compile_definitions(tst_potentialtextcarrier PRIVATE
   "QET_TEST_BINARY_PATH=\"$<TARGET_FILE:qelectrotech>\"")
 
+# With SOURCE_DATE_EPOCH set, --export-pdf writes the same bytes for the
+# same project in every run. Exports examples/741.qet several times, in
+# separate processes.
+add_executable(
+  tst_pdfreproducible
+  tst_pdfreproducible.cpp)
+add_test(NAME tst_pdfreproducible COMMAND tst_pdfreproducible)
+add_dependencies(tst_pdfreproducible qelectrotech)
+target_link_libraries(tst_pdfreproducible PRIVATE Qt::Test)
+target_compile_definitions(tst_pdfreproducible PRIVATE
+  "QET_TEST_BINARY_PATH=\"$<TARGET_FILE:qelectrotech>\""
+  "QET_EXAMPLES_DIR=\"${QET_DIR}/examples\"")
+
 # Hops where wires cross (issue #436): the geometry in wirehops.cpp, and
 # through the real binary, that --resave keeps the project setting and
 # adds nothing to a project without it.

tests/qttest/tst_pdfreproducible.cpp

@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+	With SOURCE_DATE_EPOCH set, --export-pdf writes the same bytes for the
+	same project in every run: the dates are the ones it names, the document
+	id comes from the project file, and the fonts come in a fixed order.
+	Without it the dates are the time of the export, as before. Exported in
+	separate processes, since what used to differ changed between runs.
+*/
+#include <QDateTime>
+#include <QDir>
+#include <QFile>
+#include <QProcess>
+#include <QTemporaryDir>
+#include <QtTest>
+
+class tst_pdfreproducible : public QObject
+{
+	Q_OBJECT
+
+	QTemporaryDir m_dir;
+	int m_run = 0;
+
+	QByteArray exportPdf(const QString &project, const QByteArray &epoch)
+	{
+		const int run = m_run++;
+		const QString home = m_dir.filePath(QStringLiteral("home%1").arg(run));
+		const QString tmp = m_dir.filePath(QStringLiteral("tmp%1").arg(run));
+		const QString out = m_dir.filePath(QStringLiteral("out%1.pdf").arg(run));
+		QDir().mkpath(home);
+		QDir().mkpath(tmp);
+		QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+		env.insert(QStringLiteral("QT_QPA_PLATFORM"), QStringLiteral("offscreen"));
+		env.insert(QStringLiteral("HOME"), home);
+		env.insert(QStringLiteral("XDG_CONFIG_HOME"), home + QStringLiteral("/.config"));
+		env.insert(QStringLiteral("XDG_DATA_HOME"), home + QStringLiteral("/.local/share"));
+		env.insert(QStringLiteral("TMPDIR"), tmp);
+		env.remove(QStringLiteral("QT_HASH_SEED"));
+		env.remove(QStringLiteral("SOURCE_DATE_EPOCH"));
+		if (!epoch.isEmpty())
+			env.insert(QStringLiteral("SOURCE_DATE_EPOCH"), QString::fromLatin1(epoch));
+
+		QProcess proc;
+		proc.setProcessEnvironment(env);
+		proc.start(QStringLiteral(QET_TEST_BINARY_PATH),
+				   {QStringLiteral("--export-pdf"), project, out});
+		if (!proc.waitForFinished(120000) || proc.exitCode() != 0)
+			return {};
+		QFile file(out);
+		if (!file.open(QIODevice::ReadOnly))
+			return {};
+		return file.readAll();
+	}
+
+	/// Every object the xref table lists starts where the table says: the
+	/// dates are rewritten after Qt writes the file, which moves them.
+	static bool xrefMatches(const QByteArray &pdf)
+	{
+		const int sx = pdf.lastIndexOf("startxref");
+		if (sx == -1)
+			return false;
+		const int xref = pdf.mid(sx + 9).trimmed().split('\n').value(0).toInt();
+		if (!pdf.mid(xref).startsWith("xref"))
+			return false;
+		const QList<QByteArray> lines = pdf.mid(xref).split('\n');
+		const QList<QByteArray> header = lines.value(1).split(' ');
+		const int first = header.value(0).toInt();
+		const int count = header.value(1).toInt();
+		for (int i = 0; i < count; ++i) {
+			const QList<QByteArray> entry = lines.value(2 + i).split(' ');
+			if (entry.value(2) != "n")
+				continue;
+			const QByteArray obj = QByteArray::number(first + i) + " 0 obj";
+			if (pdf.mid(entry.value(0).toInt(), obj.size()) != obj)
+				return false;
+		}
+		return count > 0;
+	}
+
+private slots:
+	void initTestCase()
+	{
+		QVERIFY(m_dir.isValid());
+		QVERIFY(QFile::exists(QStringLiteral(QET_TEST_BINARY_PATH)));
+	}
+
+	void sameBytesEveryRun()
+	{
+		// A project with no cross-reference links: their order is fixed
+		// separately.
+		const QString project =
+			QStringLiteral(QET_EXAMPLES_DIR) + QStringLiteral("/741.qet");
+		QVERIFY2(QFile::exists(project), "examples/741.qet not found");
+
+		const QByteArray first = exportPdf(project, "1700000000");
+		QVERIFY(!first.isEmpty());
+		QVERIFY(first.contains("/CreationDate (D:20231114221320Z)"));
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+		QVERIFY(first.contains("xmp:CreateDate=\"2023-11-14T22:13:20Z\""));
+#endif
+		QVERIFY2(xrefMatches(first), "the xref table does not match the file");
+		for (int i = 0; i < 3; ++i)
+			QVERIFY2(exportPdf(project, "1700000000") == first,
+					 "two exports of the same project differ");
+	}
+
+	void nowWithoutTheVariable()
+	{
+		const QString project =
+			QStringLiteral(QET_EXAMPLES_DIR) + QStringLiteral("/741.qet");
+		const QByteArray pdf = exportPdf(project, QByteArray());
+		QVERIFY(!pdf.isEmpty());
+		const QByteArray year =
+			"/CreationDate (D:" + QByteArray::number(QDate::currentDate().year());
+		QVERIFY(pdf.contains(year));
+	}
+};
+
+QTEST_MAIN(tst_pdfreproducible)
+#include "tst_pdfreproducible.moc"