Python: Switch pyls on interpreter change

Change-Id: I458b635986a55003a1e7254e27e2df9667704273
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

8 files changed, 444 insertions, 314 deletions

diff --git a/src/plugins/python/CMakeLists.txt b/src/plugins/python/CMakeLists.txt
index 27f45669f7..7ce8b21e06 100644
--- a/src/plugins/python/CMakeLists.txt
+++ b/src/plugins/python/CMakeLists.txt
@@ -12,4 +12,5 @@ add_qtc_plugin(Python
     pythonrunconfiguration.cpp pythonrunconfiguration.h
     pythonsettings.cpp pythonsettings.h
     pythonscanner.cpp pythonscanner.h
+    pythonutils.cpp pythonutils.h
 )
diff --git a/src/plugins/python/python.pro b/src/plugins/python/python.pro
index ec4ea74c06..29c53be779 100644
--- a/src/plugins/python/python.pro
+++ b/src/plugins/python/python.pro
@@ -13,7 +13,8 @@ HEADERS += \
     pythonproject.h \
     pythonrunconfiguration.h \
     pythonscanner.h \
-    pythonsettings.h
+    pythonsettings.h \
+    pythonutils.h
 
 SOURCES += \
     pythonplugin.cpp \
@@ -23,7 +24,8 @@ SOURCES += \
     pythonproject.cpp \
     pythonrunconfiguration.cpp \
     pythonscanner.cpp \
-    pythonsettings.cpp
+    pythonsettings.cpp \
+    pythonutils.cpp
 
 RESOURCES += \
     python.qrc
diff --git a/src/plugins/python/python.qbs b/src/plugins/python/python.qbs
index 552186f8c9..9fd37a4777 100644
--- a/src/plugins/python/python.qbs
+++ b/src/plugins/python/python.qbs
@@ -33,6 +33,8 @@ QtcPlugin {
             "pythonscanner.cpp",
             "pythonsettings.cpp",
             "pythonsettings.h",
+            "pythonutils.cpp",
+            "pythonutils.h",
         ]
     }
 }
diff --git a/src/plugins/python/pythoneditor.cpp b/src/plugins/python/pythoneditor.cpp
index 8422eb221f..6481897e69 100644
--- a/src/plugins/python/pythoneditor.cpp
+++ b/src/plugins/python/pythoneditor.cpp
@@ -27,327 +27,22 @@
 #include "pythonconstants.h"
 #include "pythonhighlighter.h"
 #include "pythonindenter.h"
-#include "pythonplugin.h"
-#include "pythonproject.h"
-#include "pythonrunconfiguration.h"
-#include "pythonsettings.h"
-
-#include <coreplugin/infobar.h>
-#include <coreplugin/progressmanager/progressmanager.h>
-
-#include <languageclient/client.h>
-#include <languageclient/languageclientinterface.h>
-#include <languageclient/languageclientmanager.h>
-
-#include <projectexplorer/session.h>
-#include <projectexplorer/target.h>
+#include "pythonutils.h"
 
 #include <texteditor/textdocument.h>
 #include <texteditor/texteditoractionhandler.h>
-#include <texteditor/texteditorconstants.h>
-
-#include <utils/executeondestruction.h>
-#include <utils/qtcassert.h>
-#include <utils/synchronousprocess.h>
-
-#include <QCoreApplication>
-#include <QFutureWatcher>
-#include <QRegularExpression>
-#include <QTimer>
-
-using namespace ProjectExplorer;
-using namespace Utils;
 
 namespace Python {
 namespace Internal {
 
-static constexpr char startPylsInfoBarId[] = "PythonEditor::StartPyls";
-static constexpr char installPylsInfoBarId[] = "PythonEditor::InstallPyls";
-static constexpr char installPylsTaskId[] = "PythonEditor::InstallPylsTask";
-
-struct PythonForProject
-{
-    FilePath path;
-    PythonProject *project = nullptr;
-
-    QString name() const
-    {
-        if (!path.exists())
-            return {};
-        if (cachedName.first != path) {
-            SynchronousProcess pythonProcess;
-            const CommandLine pythonVersionCommand(path, {"--version"});
-            SynchronousProcessResponse response = pythonProcess.runBlocking(pythonVersionCommand);
-            cachedName.first = path;
-            cachedName.second = response.allOutput().trimmed();
-        }
-        return cachedName.second;
-    }
-
-private:
-    mutable QPair<FilePath, QString> cachedName;
-};
-
-static PythonForProject detectPython(TextEditor::TextDocument *document)
-{
-    PythonForProject python;
-
-    python.project = qobject_cast<PythonProject *>(
-        SessionManager::projectForFile(document->filePath()));
-    if (!python.project)
-        python.project = qobject_cast<PythonProject *>(SessionManager::startupProject());
-
-    if (python.project) {
-        if (auto target = python.project->activeTarget()) {
-            if (auto runConfig = qobject_cast<PythonRunConfiguration *>(
-                    target->activeRunConfiguration())) {
-                python.path = FilePath::fromString(runConfig->interpreter());
-            }
-        }
-    }
-
-    if (!python.path.exists())
-        python.path = PythonSettings::defaultInterpreter().command;
-
-    if (!python.path.exists() && !PythonSettings::interpreters().isEmpty())
-        python.path = PythonSettings::interpreters().first().command;
-
-    return python;
-}
-
-FilePath getPylsModulePath(CommandLine pylsCommand)
-{
-    pylsCommand.addArg("-h");
-    SynchronousProcess pythonProcess;
-    pythonProcess.setEnvironment(pythonProcess.environment() + QStringList("PYTHONVERBOSE=x"));
-    SynchronousProcessResponse response = pythonProcess.runBlocking(pylsCommand);
-
-    static const QString pylsInitPattern = "(.*)"
-                                           + QRegularExpression::escape(
-                                               QDir::toNativeSeparators("/pyls/__init__.py"))
-                                           + '$';
-    static const QRegularExpression regexCached(" matches " + pylsInitPattern,
-                                                QRegularExpression::MultilineOption);
-    static const QRegularExpression regexNotCached(" code object from " + pylsInitPattern,
-                                                   QRegularExpression::MultilineOption);
-
-    const QString &output = response.allOutput();
-    for (auto regex : {regexCached, regexNotCached}) {
-        QRegularExpressionMatch result = regex.match(output);
-        if (result.hasMatch())
-            return FilePath::fromUserInput(result.captured(1));
-    }
-    return {};
-}
-
-struct PythonLanguageServerState
-{
-    enum { CanNotBeInstalled, CanBeInstalled, AlreadyInstalled, AlreadyConfigured } state;
-    FilePath pylsModulePath;
-};
-
-static QList<const LanguageClient::StdIOSettings *> configuredPythonLanguageServer(
-    Core::IDocument *doc)
-{
-    using namespace LanguageClient;
-    QList<const StdIOSettings *> result;
-    for (const BaseSettings *setting : LanguageClientManager::currentSettings()) {
-        if (setting->m_languageFilter.isSupported(doc))
-            result << dynamic_cast<const StdIOSettings *>(setting);
-    }
-    return result;
-}
-
-static PythonLanguageServerState checkPythonLanguageServer(const FilePath &python,
-                                                           TextEditor::TextDocument *document)
-{
-    using namespace LanguageClient;
-    SynchronousProcess pythonProcess;
-    const CommandLine pythonLShelpCommand(python, {"-m", "pyls", "-h"});
-    SynchronousProcessResponse response = pythonProcess.runBlocking(pythonLShelpCommand);
-    if (response.allOutput().contains("Python Language Server")) {
-        const FilePath &modulePath = getPylsModulePath(pythonLShelpCommand);
-        for (const StdIOSettings *serverSetting : configuredPythonLanguageServer(document)) {
-            CommandLine serverCommand(FilePath::fromUserInput(serverSetting->m_executable),
-                                      serverSetting->arguments(),
-                                      CommandLine::Raw);
-
-            if (modulePath == getPylsModulePath(serverCommand))
-                return {PythonLanguageServerState::AlreadyConfigured, FilePath()};
-        }
-
-        return {PythonLanguageServerState::AlreadyInstalled, getPylsModulePath(pythonLShelpCommand)};
-    }
-
-    const CommandLine pythonPipVersionCommand(python, {"-m", "pip", "-V"});
-    response = pythonProcess.runBlocking(pythonPipVersionCommand);
-    if (response.allOutput().startsWith("pip "))
-        return {PythonLanguageServerState::CanBeInstalled, FilePath()};
-    else
-        return {PythonLanguageServerState::CanNotBeInstalled, FilePath()};
-}
-
-static LanguageClient::Client *registerLanguageServer(const PythonForProject &python)
-{
-    auto *settings = new LanguageClient::StdIOSettings();
-    settings->m_executable = python.path.toString();
-    settings->m_arguments = "-m pyls";
-    settings->m_name = PythonEditorFactory::tr("Python Language Server (%1)").arg(python.name());
-    settings->m_languageFilter.mimeTypes = QStringList(Constants::C_PY_MIMETYPE);
-    LanguageClient::LanguageClientManager::registerClientSettings(settings);
-    return LanguageClient::LanguageClientManager::clientForSetting(settings).value(0);
-}
-
-class PythonLSInstallHelper : public QObject
-{
-    Q_OBJECT
-public:
-    PythonLSInstallHelper(const PythonForProject &python, QPointer<TextEditor::TextDocument> document)
-        : m_python(python)
-        , m_document(document)
-    {
-        m_watcher.setFuture(m_future.future());
-    }
-
-    void run()
-    {
-        Core::ProgressManager::addTask(m_future.future(), "Install PyLS", installPylsTaskId);
-        connect(&m_process,
-                QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
-                this,
-                &PythonLSInstallHelper::installFinished);
-        connect(&m_process,
-                &QProcess::readyReadStandardError,
-                this,
-                &PythonLSInstallHelper::errorAvailable);
-        connect(&m_process,
-                &QProcess::readyReadStandardOutput,
-                this,
-                &PythonLSInstallHelper::outputAvailable);
-
-        connect(&m_killTimer, &QTimer::timeout, this, &PythonLSInstallHelper::cancel);
-        connect(&m_watcher, &QFutureWatcher<void>::canceled, this, &PythonLSInstallHelper::cancel);
-
-        // on windows the pyls 0.28.3 crashes with pylint so just install the pyflakes linter
-        const QString &pylsVersion = HostOsInfo::isWindowsHost()
-                                         ? QString{"python-language-server[pyflakes]"}
-                                         : QString{"python-language-server[all]"};
-
-        m_process.start(m_python.path.toString(),
-                        {"-m", "pip", "install", pylsVersion});
-
-        Core::MessageManager::write(tr("Running '%1 %2' to install python language server")
-                                        .arg(m_process.program(), m_process.arguments().join(' ')));
-
-        m_killTimer.setSingleShot(true);
-        m_killTimer.start(5 /*minutes*/ * 60 * 1000);
-    }
-
-private:
-    void cancel()
-    {
-        SynchronousProcess::stopProcess(m_process);
-        Core::MessageManager::write(
-            tr("The Python language server installation canceled by %1.")
-                .arg(m_killTimer.isActive() ? tr("user") : tr("time out")));
-    }
-
-    void installFinished(int exitCode, QProcess::ExitStatus exitStatus)
-    {
-        m_future.reportFinished();
-        if (exitStatus == QProcess::NormalExit && exitCode == 0) {
-            if (LanguageClient::Client *client = registerLanguageServer(m_python))
-                LanguageClient::LanguageClientManager::reOpenDocumentWithClient(m_document, client);
-        } else {
-            Core::MessageManager::write(
-                tr("Installing the Python language server failed with exit code %1").arg(exitCode));
-        }
-        deleteLater();
-    }
-    void outputAvailable()
-    {
-        const QString &stdOut = QString::fromLocal8Bit(m_process.readAllStandardOutput().trimmed());
-        if (!stdOut.isEmpty())
-            Core::MessageManager::write(stdOut);
-    }
-
-    void errorAvailable()
-    {
-        const QString &stdErr = QString::fromLocal8Bit(m_process.readAllStandardError().trimmed());
-        if (!stdErr.isEmpty())
-            Core::MessageManager::write(stdErr);
-    }
-
-    QFutureInterface<void> m_future;
-    QFutureWatcher<void> m_watcher;
-    QProcess m_process;
-    QTimer m_killTimer;
-    const PythonForProject m_python;
-    QPointer<TextEditor::TextDocument> m_document;
-};
-
-static void installPythonLanguageServer(const PythonForProject &python,
-                                        QPointer<TextEditor::TextDocument> document)
-{
-    document->infoBar()->removeInfo(installPylsInfoBarId);
-
-    auto install = new PythonLSInstallHelper(python, document);
-    install->run();
-}
-
-static void setupPythonLanguageServer(const PythonForProject &python,
-                                      QPointer<TextEditor::TextDocument> document)
-{
-    document->infoBar()->removeInfo(startPylsInfoBarId);
-    if (LanguageClient::Client *client = registerLanguageServer(python))
-        LanguageClient::LanguageClientManager::reOpenDocumentWithClient(document, client);
-}
-
-static void updateEditorInfoBar(const PythonForProject &python, TextEditor::TextDocument *document)
-{
-    const PythonLanguageServerState &lsState = checkPythonLanguageServer(python.path, document);
-
-    if (lsState.state == PythonLanguageServerState::CanNotBeInstalled
-        || lsState.state == PythonLanguageServerState::AlreadyConfigured) {
-        return;
-    }
-
-    Core::InfoBar *infoBar = document->infoBar();
-    if (lsState.state == PythonLanguageServerState::CanBeInstalled
-        && infoBar->canInfoBeAdded(installPylsInfoBarId)) {
-        auto message
-            = PythonEditorFactory::tr(
-                  "Install and set up Python language server (PyLS) for %1 (%2). "
-                  "The language server provides Python specific completions and annotations.")
-                  .arg(python.name(), python.path.toUserOutput());
-        Core::InfoBarEntry info(installPylsInfoBarId,
-                                message,
-                                Core::InfoBarEntry::GlobalSuppression::Enabled);
-        info.setCustomButtonInfo(TextEditor::BaseTextEditor::tr("Install"),
-                                 [=]() { installPythonLanguageServer(python, document); });
-        infoBar->addInfo(info);
-    } else if (lsState.state == PythonLanguageServerState::AlreadyInstalled
-               && infoBar->canInfoBeAdded(startPylsInfoBarId)) {
-        auto message = PythonEditorFactory::tr("Found a Python language server for %1 (%2). "
-                                               "Should this one be set up for this document?")
-                           .arg(python.name(), python.path.toUserOutput());
-        Core::InfoBarEntry info(startPylsInfoBarId,
-                                message,
-                                Core::InfoBarEntry::GlobalSuppression::Enabled);
-        info.setCustomButtonInfo(TextEditor::BaseTextEditor::tr("Setup"),
-                                 [=]() { setupPythonLanguageServer(python, document); });
-        infoBar->addInfo(info);
-    }
-}
-
 static void documentOpened(Core::IDocument *document)
 {
     auto textDocument = qobject_cast<TextEditor::TextDocument *>(document);
     if (!textDocument || textDocument->mimeType() != Constants::C_PY_MIMETYPE)
         return;
 
-    const PythonForProject &python = detectPython(textDocument);
-    if (!python.path.exists())
+    const Utils::FilePath &python = detectPython(textDocument->filePath());
+    if (!python.exists())
         return;
 
     updateEditorInfoBar(python, textDocument);
@@ -368,7 +63,7 @@ PythonEditorFactory::PythonEditorFactory()
     setDocumentCreator([] { return new TextEditor::TextDocument(Constants::C_PYTHONEDITOR_ID); });
     setIndenterCreator([](QTextDocument *doc) { return new PythonIndenter(doc); });
     setSyntaxHighlighterCreator([] { return new PythonHighlighter; });
-    setCommentDefinition(CommentDefinition::HashStyle);
+    setCommentDefinition(Utils::CommentDefinition::HashStyle);
     setParenthesesMatchingEnabled(true);
     setCodeFoldingSupported(true);
 
@@ -378,5 +73,3 @@ PythonEditorFactory::PythonEditorFactory()
 
 } // namespace Internal
 } // namespace Python
-
-#include "pythoneditor.moc"
diff --git a/src/plugins/python/pythonrunconfiguration.cpp b/src/plugins/python/pythonrunconfiguration.cpp
index bb61f275ae..53245b1632 100644
--- a/src/plugins/python/pythonrunconfiguration.cpp
+++ b/src/plugins/python/pythonrunconfiguration.cpp
@@ -23,20 +23,26 @@
 **
 ****************************************************************************/
 
+#include "pythonrunconfiguration.h"
+
 #include "pythonconstants.h"
 #include "pythonproject.h"
-#include "pythonrunconfiguration.h"
 #include "pythonsettings.h"
+#include "pythonutils.h"
 
 #include <coreplugin/icore.h>
 #include <coreplugin/editormanager/editormanager.h>
 
+#include <languageclient/languageclientmanager.h>
+
 #include <projectexplorer/localenvironmentaspect.h>
 #include <projectexplorer/projectconfigurationaspects.h>
 #include <projectexplorer/runconfigurationaspects.h>
 #include <projectexplorer/target.h>
 #include <projectexplorer/taskhub.h>
 
+#include <texteditor/textdocument.h>
+
 #include <utils/fileutils.h>
 #include <utils/outputformatter.h>
 #include <utils/theme/theme.h>
@@ -248,6 +254,8 @@ PythonRunConfiguration::PythonRunConfiguration(Target *target, Core::Id id)
 {
     auto interpreterAspect = addAspect<InterpreterAspect>();
     interpreterAspect->setSettingsKey("PythonEditor.RunConfiguation.Interpreter");
+    connect(interpreterAspect, &InterpreterAspect::changed,
+            this, &PythonRunConfiguration::updateLanguageServer);
 
     connect(PythonSettings::instance(), &PythonSettings::interpretersChanged,
             interpreterAspect, &InterpreterAspect::updateInterpreters);
@@ -283,6 +291,33 @@ void PythonRunConfiguration::doAdditionalSetup(const RunConfigurationCreationInf
     updateTargetInformation();
 }
 
+void PythonRunConfiguration::updateLanguageServer()
+{
+    using namespace LanguageClient;
+
+    const FilePath python(FilePath::fromUserInput(interpreter()));
+
+    if (const StdIOSettings *lsSetting = languageServerForPython(python)) {
+        if (Client *client = LanguageClientManager::clientForSetting(lsSetting).value(0)) {
+            for (FilePath &file : project()->files(Project::AllFiles)) {
+                if (auto document = TextEditor::TextDocument::textDocumentForFilePath(file)) {
+                    if (document->mimeType() == Constants::C_PY_MIMETYPE) {
+                        resetEditorInfoBar(document);
+                        LanguageClientManager::reOpenDocumentWithClient(document, client);
+                    }
+                }
+            }
+        }
+    }
+
+    for (FilePath &file : project()->files(Project::AllFiles)) {
+        if (auto document = TextEditor::TextDocument::textDocumentForFilePath(file)) {
+            if (document->mimeType() == Constants::C_PY_MIMETYPE)
+                updateEditorInfoBar(python, document);
+        }
+    }
+}
+
 bool PythonRunConfiguration::supportsDebugger() const
 {
     return true;
diff --git a/src/plugins/python/pythonrunconfiguration.h b/src/plugins/python/pythonrunconfiguration.h
index bb5139e615..6d5a13683a 100644
--- a/src/plugins/python/pythonrunconfiguration.h
+++ b/src/plugins/python/pythonrunconfiguration.h
@@ -46,6 +46,7 @@ public:
 
 private:
     void doAdditionalSetup(const ProjectExplorer::RunConfigurationCreationInfo &) final;
+    void updateLanguageServer();
 
     bool supportsDebugger() const;
     QString mainScript() const;
diff --git a/src/plugins/python/pythonutils.cpp b/src/plugins/python/pythonutils.cpp
new file mode 100644
index 0000000000..29fc14953b
--- /dev/null
+++ b/src/plugins/python/pythonutils.cpp
@@ -0,0 +1,353 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "pythonutils.h"
+
+#include "pythonconstants.h"
+#include "pythonproject.h"
+#include "pythonrunconfiguration.h"
+#include "pythonsettings.h"
+
+#include <coreplugin/infobar.h>
+#include <coreplugin/progressmanager/progressmanager.h>
+
+#include <languageclient/languageclientsettings.h>
+#include <languageclient/languageclientmanager.h>
+
+#include <projectexplorer/session.h>
+#include <projectexplorer/target.h>
+
+#include <texteditor/textdocument.h>
+
+#include <utils/synchronousprocess.h>
+
+#include <QDir>
+#include <QFutureWatcher>
+#include <QRegularExpression>
+#include <QTimer>
+
+using namespace Utils;
+
+namespace Python {
+namespace Internal {
+
+static constexpr char startPylsInfoBarId[] = "Python::StartPyls";
+static constexpr char installPylsInfoBarId[] = "Python::InstallPyls";
+static constexpr char installPylsTaskId[] = "Python::InstallPylsTask";
+static constexpr char pythonUtilsTrContext[] = "Python::Utils";
+
+struct PythonLanguageServerState
+{
+    enum { CanNotBeInstalled, CanBeInstalled, AlreadyInstalled, AlreadyConfigured } state;
+    FilePath pylsModulePath;
+};
+
+static QString pythonName(const FilePath &pythonPath)
+{
+    static QHash<FilePath, QString> nameForPython;
+    if (!pythonPath.exists())
+        return {};
+    QString name = nameForPython.value(pythonPath);
+    if (name.isEmpty()) {
+        SynchronousProcess pythonProcess;
+        pythonProcess.setTimeoutS(2);
+        const CommandLine pythonVersionCommand(pythonPath, {"--version"});
+        const SynchronousProcessResponse response = pythonProcess.runBlocking(pythonVersionCommand);
+        if (response.result != SynchronousProcessResponse::Finished)
+            return {};
+        name = response.allOutput().trimmed();
+        nameForPython[pythonPath] = name;
+    }
+    return name;
+}
+
+FilePath getPylsModulePath(CommandLine pylsCommand)
+{
+    pylsCommand.addArg("-h");
+    SynchronousProcess pythonProcess;
+    pythonProcess.setEnvironment(pythonProcess.environment() + QStringList("PYTHONVERBOSE=x"));
+    SynchronousProcessResponse response = pythonProcess.runBlocking(pylsCommand);
+
+    static const QString pylsInitPattern = "(.*)"
+                                           + QRegularExpression::escape(
+                                               QDir::toNativeSeparators("/pyls/__init__.py"))
+                                           + '$';
+    static const QRegularExpression regexCached(" matches " + pylsInitPattern,
+                                                QRegularExpression::MultilineOption);
+    static const QRegularExpression regexNotCached(" code object from " + pylsInitPattern,
+                                                   QRegularExpression::MultilineOption);
+
+    const QString &output = response.allOutput();
+    for (auto regex : {regexCached, regexNotCached}) {
+        QRegularExpressionMatch result = regex.match(output);
+        if (result.hasMatch())
+            return FilePath::fromUserInput(result.captured(1));
+    }
+    return {};
+}
+
+QList<const LanguageClient::StdIOSettings *> configuredPythonLanguageServer()
+{
+    using namespace LanguageClient;
+    QList<const StdIOSettings *> result;
+    for (const BaseSettings *setting : LanguageClientManager::currentSettings()) {
+        if (setting->m_languageFilter.isSupported(FilePath::fromString("foo.py"),
+                                                  Constants::C_PY_MIMETYPE)) {
+            result << dynamic_cast<const StdIOSettings *>(setting);
+        }
+    }
+    return result;
+}
+
+static PythonLanguageServerState checkPythonLanguageServer(const FilePath &python)
+{
+    using namespace LanguageClient;
+    SynchronousProcess pythonProcess;
+    const CommandLine pythonLShelpCommand(python, {"-m", "pyls", "-h"});
+    SynchronousProcessResponse response = pythonProcess.runBlocking(pythonLShelpCommand);
+    if (response.allOutput().contains("Python Language Server")) {
+        const FilePath &modulePath = getPylsModulePath(pythonLShelpCommand);
+        for (const StdIOSettings *serverSetting : configuredPythonLanguageServer()) {
+            if (modulePath == getPylsModulePath(serverSetting->command()))
+                return {PythonLanguageServerState::AlreadyConfigured, FilePath()};
+        }
+
+        return {PythonLanguageServerState::AlreadyInstalled, getPylsModulePath(pythonLShelpCommand)};
+    }
+
+    const CommandLine pythonPipVersionCommand(python, {"-m", "pip", "-V"});
+    response = pythonProcess.runBlocking(pythonPipVersionCommand);
+    if (response.allOutput().startsWith("pip "))
+        return {PythonLanguageServerState::CanBeInstalled, FilePath()};
+    else
+        return {PythonLanguageServerState::CanNotBeInstalled, FilePath()};
+}
+
+FilePath detectPython(const FilePath &documentPath)
+{
+    FilePath python;
+
+    PythonProject *project = qobject_cast<PythonProject *>(
+        ProjectExplorer::SessionManager::projectForFile(documentPath));
+    if (!project)
+        project = qobject_cast<PythonProject *>(ProjectExplorer::SessionManager::startupProject());
+
+    if (project) {
+        if (auto target = project->activeTarget()) {
+            if (auto runConfig = qobject_cast<PythonRunConfiguration *>(
+                    target->activeRunConfiguration())) {
+                python = FilePath::fromString(runConfig->interpreter());
+            }
+        }
+    }
+
+    if (!python.exists())
+        python = PythonSettings::defaultInterpreter().command;
+
+    if (!python.exists() && !PythonSettings::interpreters().isEmpty())
+        python = PythonSettings::interpreters().first().command;
+
+    return python;
+}
+
+const LanguageClient::StdIOSettings *languageServerForPython(const FilePath &python)
+{
+    return findOrDefault(configuredPythonLanguageServer(),
+                         [pythonModulePath = getPylsModulePath(CommandLine(python, {"-m", "pyls"}))](
+                             const LanguageClient::StdIOSettings *setting) {
+                             return getPylsModulePath(setting->command()) == pythonModulePath;
+                         });
+}
+
+static LanguageClient::Client *registerLanguageServer(const FilePath &python)
+{
+    auto *settings = new LanguageClient::StdIOSettings();
+    settings->m_executable = python.toString();
+    settings->m_arguments = "-m pyls";
+    settings->m_name = QCoreApplication::translate(pythonUtilsTrContext,
+                                                   "Python Language Server (%1)")
+                           .arg(pythonName(python));
+    settings->m_languageFilter.mimeTypes = QStringList(Constants::C_PY_MIMETYPE);
+    LanguageClient::LanguageClientManager::registerClientSettings(settings);
+    return LanguageClient::LanguageClientManager::clientForSetting(settings).value(0);
+}
+
+class PythonLSInstallHelper : public QObject
+{
+    Q_OBJECT
+public:
+    PythonLSInstallHelper(const FilePath &python, QPointer<TextEditor::TextDocument> document)
+        : m_python(python)
+        , m_document(document)
+    {
+        m_watcher.setFuture(m_future.future());
+    }
+
+    void run()
+    {
+        Core::ProgressManager::addTask(m_future.future(), "Install PyLS", installPylsTaskId);
+        connect(&m_process,
+                QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
+                this,
+                &PythonLSInstallHelper::installFinished);
+        connect(&m_process,
+                &QProcess::readyReadStandardError,
+                this,
+                &PythonLSInstallHelper::errorAvailable);
+        connect(&m_process,
+                &QProcess::readyReadStandardOutput,
+                this,
+                &PythonLSInstallHelper::outputAvailable);
+
+        connect(&m_killTimer, &QTimer::timeout, this, &PythonLSInstallHelper::cancel);
+        connect(&m_watcher, &QFutureWatcher<void>::canceled, this, &PythonLSInstallHelper::cancel);
+
+        // on windows the pyls 0.28.3 crashes with pylint so just install the pyflakes linter
+        const QString &pylsVersion = HostOsInfo::isWindowsHost()
+                                         ? QString{"python-language-server[pyflakes]"}
+                                         : QString{"python-language-server[all]"};
+
+        m_process.start(m_python.toString(), {"-m", "pip", "install", pylsVersion});
+
+        Core::MessageManager::write(tr("Running '%1 %2' to install python language server")
+                                        .arg(m_process.program(), m_process.arguments().join(' ')));
+
+        m_killTimer.setSingleShot(true);
+        m_killTimer.start(5 /*minutes*/ * 60 * 1000);
+    }
+
+private:
+    void cancel()
+    {
+        SynchronousProcess::stopProcess(m_process);
+        Core::MessageManager::write(
+            tr("The Python language server installation canceled by %1.")
+                .arg(m_killTimer.isActive() ? tr("user") : tr("time out")));
+    }
+
+    void installFinished(int exitCode, QProcess::ExitStatus exitStatus)
+    {
+        m_future.reportFinished();
+        if (exitStatus == QProcess::NormalExit && exitCode == 0) {
+            if (LanguageClient::Client *client = registerLanguageServer(m_python))
+                LanguageClient::LanguageClientManager::reOpenDocumentWithClient(m_document, client);
+        } else {
+            Core::MessageManager::write(
+                tr("Installing the Python language server failed with exit code %1").arg(exitCode));
+        }
+        deleteLater();
+    }
+
+    void outputAvailable()
+    {
+        const QString &stdOut = QString::fromLocal8Bit(m_process.readAllStandardOutput().trimmed());
+        if (!stdOut.isEmpty())
+            Core::MessageManager::write(stdOut);
+    }
+
+    void errorAvailable()
+    {
+        const QString &stdErr = QString::fromLocal8Bit(m_process.readAllStandardError().trimmed());
+        if (!stdErr.isEmpty())
+            Core::MessageManager::write(stdErr);
+    }
+
+    QFutureInterface<void> m_future;
+    QFutureWatcher<void> m_watcher;
+    QProcess m_process;
+    QTimer m_killTimer;
+    const FilePath m_python;
+    QPointer<TextEditor::TextDocument> m_document;
+};
+
+static void installPythonLanguageServer(const FilePath &python,
+                                        QPointer<TextEditor::TextDocument> document)
+{
+    document->infoBar()->removeInfo(installPylsInfoBarId);
+
+    auto install = new PythonLSInstallHelper(python, document);
+    install->run();
+}
+
+static void setupPythonLanguageServer(const FilePath &python,
+                                      QPointer<TextEditor::TextDocument> document)
+{
+    document->infoBar()->removeInfo(startPylsInfoBarId);
+    if (LanguageClient::Client *client = registerLanguageServer(python))
+        LanguageClient::LanguageClientManager::reOpenDocumentWithClient(document, client);
+}
+
+void updateEditorInfoBar(const FilePath &python, TextEditor::TextDocument *document)
+{
+    const PythonLanguageServerState &lsState = checkPythonLanguageServer(python);
+
+    if (lsState.state == PythonLanguageServerState::CanNotBeInstalled
+        || lsState.state == PythonLanguageServerState::AlreadyConfigured) {
+        return;
+    }
+
+    Core::InfoBar *infoBar = document->infoBar();
+    infoBar->removeInfo(installPylsInfoBarId);
+    infoBar->removeInfo(startPylsInfoBarId);
+    if (lsState.state == PythonLanguageServerState::CanBeInstalled
+        && infoBar->canInfoBeAdded(installPylsInfoBarId)) {
+        auto message
+            =  QCoreApplication::translate(pythonUtilsTrContext,
+                  "Install and set up Python language server (PyLS) for %1 (%2). "
+                  "The language server provides Python specific completions and annotations.")
+                  .arg(pythonName(python), python.toUserOutput());
+        Core::InfoBarEntry info(installPylsInfoBarId,
+                                message,
+                                Core::InfoBarEntry::GlobalSuppression::Enabled);
+        info.setCustomButtonInfo(QCoreApplication::translate(pythonUtilsTrContext, "Install"),
+                                 [=]() { installPythonLanguageServer(python, document); });
+        infoBar->addInfo(info);
+    } else if (lsState.state == PythonLanguageServerState::AlreadyInstalled
+               && infoBar->canInfoBeAdded(startPylsInfoBarId)) {
+        auto message = QCoreApplication::translate(pythonUtilsTrContext,
+                                                   "Found a Python language server for %1 (%2). "
+                                                   "Should this one be set up for this document?")
+                           .arg(pythonName(python), python.toUserOutput());
+        Core::InfoBarEntry info(startPylsInfoBarId,
+                                message,
+                                Core::InfoBarEntry::GlobalSuppression::Enabled);
+        info.setCustomButtonInfo(QCoreApplication::translate(pythonUtilsTrContext, "Setup"),
+                                 [=]() { setupPythonLanguageServer(python, document); });
+        infoBar->addInfo(info);
+    }
+}
+
+void resetEditorInfoBar(TextEditor::TextDocument *document)
+{
+    Core::InfoBar *infoBar = document->infoBar();
+    infoBar->removeInfo(installPylsInfoBarId);
+    infoBar->removeInfo(startPylsInfoBarId);
+}
+
+} // namespace Internal
+} // namespace Python
+
+#include "pythonutils.moc"
+
diff --git a/src/plugins/python/pythonutils.h b/src/plugins/python/pythonutils.h
new file mode 100644
index 0000000000..f376a4d749
--- /dev/null
+++ b/src/plugins/python/pythonutils.h
@@ -0,0 +1,43 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include <utils/fileutils.h>
+
+#pragma once
+
+namespace TextEditor { class TextDocument; }
+namespace LanguageClient { class StdIOSettings; }
+
+namespace Python {
+namespace Internal {
+
+QList<const LanguageClient::StdIOSettings *> configuredPythonLanguageServers();
+const LanguageClient::StdIOSettings *languageServerForPython(const Utils::FilePath &python);
+Utils::FilePath detectPython(const Utils::FilePath &NdocumentPath);
+void updateEditorInfoBar(const Utils::FilePath &python, TextEditor::TextDocument *document);
+void resetEditorInfoBar(TextEditor::TextDocument *document);
+
+} // namespace Internal
+} // namespace Python