Fix wrong behavior when reading text

Also add another 'file read error' status.

Closes #19254.
PR #19262.

.gitattributes

@@ -5,3 +5,5 @@ core.eol=lf
 *.png binary
 *.qm binary
 *.zip binary
+
+test/testdata/crlf.txt text eol=crlf

.pre-commit-config.yaml

@@ -33,19 +33,19 @@ repos:
       args: ["--fix=lf"]
       exclude: |
         (?x)^(
-          compile_commands.json |
           src/webui/www/private/css/lib/.* |
-          src/webui/www/private/scripts/lib/.*
+          src/webui/www/private/scripts/lib/.* |
+          test/testdata/crlf.txt
         )$
 
     - id: end-of-file-fixer
       name: Check trailing newlines
       exclude: |
         (?x)^(
-          compile_commands.json |
           configure |
           src/webui/www/private/css/lib/.* |
-          src/webui/www/private/scripts/lib/.*
+          src/webui/www/private/scripts/lib/.* |
+          test/testdata/crlf.txt
         )$
       exclude_types:
         - svg

src/base/utils/io.cpp

@@ -89,16 +89,37 @@ nonstd::expected<QByteArray, Utils::IO::ReadError> Utils::IO::readFile(const Pat
         return nonstd::make_unexpected(ReadError {ReadError::ExceedSize, message});
     }
 
-    // Do not use `QIODevice::readAll()` it won't stop when reading `/dev/zero`
-    const QByteArray data = file.read(fileSize);
-    if (const qint64 dataSize = data.size(); dataSize != fileSize)
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 5, 0))
+    QByteArray ret {fileSize, Qt::Uninitialized};
+#else
+    QByteArray ret {static_cast<int>(fileSize), Qt::Uninitialized};
+#endif
+    const qint64 actualSize = file.read(ret.data(), fileSize);
+
+    if (actualSize < 0)
+    {
+        const QString message = QCoreApplication::translate("Utils::IO", "File read error. File: \"%1\". Error: \"%2\"")
+            .arg(file.fileName(), file.errorString());
+        return nonstd::make_unexpected(ReadError {ReadError::Failed, message});
+    }
+
+    if (actualSize < fileSize)
+    {
+        // `QIODevice::Text` will convert CRLF to LF on-the-fly and affects return value
+        // of `qint64 QIODevice::read(char *data, qint64 maxSize)`
+        if (additionalMode.testFlag(QIODevice::Text))
+        {
+            ret.truncate(actualSize);
+        }
+        else
         {
             const QString message = QCoreApplication::translate("Utils::IO", "Read size mismatch. File: \"%1\". Expected: %2. Actual: %3")
-            .arg(file.fileName(), QString::number(fileSize), QString::number(dataSize));
+                .arg(file.fileName(), QString::number(fileSize), QString::number(actualSize));
             return nonstd::make_unexpected(ReadError {ReadError::SizeMismatch, message});
         }
+    }
 
-    return data;
+    return ret;
 }
 
 nonstd::expected<void, QString> Utils::IO::saveToFile(const Path &path, const QByteArray &data)

src/base/utils/io.h

@@ -89,6 +89,7 @@ namespace Utils::IO
         {
             NotExist,
             ExceedSize,
+            Failed,  // `read()` operation failed
             SizeMismatch
         };
 

src/webui/webapplication.cpp

@@ -516,6 +516,7 @@ void WebApplication::sendFile(const Path &path)
             LogMsg(message, Log::WARNING);
             throw InternalServerErrorHTTPError(readResult.error().message);
 
+        case Utils::IO::ReadError::Failed:
         case Utils::IO::ReadError::SizeMismatch:
             LogMsg(message, Log::WARNING);
             throw InternalServerErrorHTTPError(readResult.error().message);

test/testdata/crlf.txt

@@ -0,0 +1,2 @@
+
+

test/testutilsio.cpp

@@ -77,6 +77,13 @@ private slots:
             QCOMPARE(readResult.value(), size10Data);
         }
 
+        {
+            const Path crlfFile = testFolder / Path(u"crlf.txt"_s);
+            const auto readResult = Utils::IO::readFile(crlfFile, -1, QIODevice::Text);
+            QCOMPARE(readResult.has_value(), true);
+            QCOMPARE(readResult.value(), "\n\n");
+        }
+
         {
             const Path nonExistFile = testFolder / Path(u".non_existent_file_1234"_s);
             const auto readResult = Utils::IO::readFile(nonExistFile, 1);