CodeAssist: Fix auto completion if function signature is shown

This reverts

    commit 3bf19030aba43e4c8326d921e2bf0b4506ea9bce.
    CodeAssist: Fragile proposals aren't closed by automatic proposals.

which fixed the case [1] but introduced the regression in case [2]. Re-
implement the fix for [1] in a different way: Check whether the new
proposal has any items to show before closing the function signature
hint.

Case [1]
  void f(int);
  void g()
  {
      f(bar // This is what we will have in the end. The steps are:
            // 1. Type "f("
            //    --> OK, function signature pop up is shown.
            // 2. Type "bar"
            //    --> OPS, function signature pop up is closed and no
            //        new completion list is shown because "bar" does
            //        not match any declarations.
  }

Case [2]
  int barman = 0;
  void f(int);
  void g()
  {
      f(bar // This is what we will have in the end. The steps are:
            // 1. Type "f("
            //    --> OK, function signature pop up is shown.
            // 2. Type "bar"
            //    --> OPS, no auto completion list for "barman" is
            //        proposed.
  }

Task-number: QTCREATORBUG-16934
Change-Id: I8456275d951de9e6fc53285a5dbcbd448d49ad08
Reviewed-by: David Schulz <david.schulz@qt.io>

7 files changed, 107 insertions, 56 deletions

diff --git a/src/plugins/texteditor/codeassist/codeassistant.cpp b/src/plugins/texteditor/codeassist/codeassistant.cpp
index 023e853d99..ab3b9907a9 100644
--- a/src/plugins/texteditor/codeassist/codeassistant.cpp
+++ b/src/plugins/texteditor/codeassist/codeassistant.cpp
@@ -181,8 +181,7 @@ void CodeAssistantPrivate::process()
             }
         }
 
-        if (!isDisplayingProposal())
-            startAutomaticProposalTimer();
+        startAutomaticProposalTimer();
     } else {
         m_assistKind = TextEditor::Completion;
     }
@@ -288,18 +287,33 @@ void CodeAssistantPrivate::displayProposal(IAssistProposal *newProposal, AssistR
 
     QScopedPointer<IAssistProposal> proposalCandidate(newProposal);
 
+    bool destroyCurrentContext = false;
     if (isDisplayingProposal()) {
         if (!m_proposal->isFragile())
             return;
-        destroyContext();
+        destroyCurrentContext = true;
     }
 
     int basePosition = proposalCandidate->basePosition();
-    if (m_editorWidget->position() < basePosition)
+    if (m_editorWidget->position() < basePosition) {
+        if (destroyCurrentContext)
+            destroyContext();
         return;
+    }
 
-    if (m_abortedBasePosition == basePosition && reason != ExplicitlyInvoked)
+    if (m_abortedBasePosition == basePosition && reason != ExplicitlyInvoked) {
+        if (destroyCurrentContext)
+            destroyContext();
         return;
+    }
+
+    const QString prefix = m_editorWidget->textAt(basePosition,
+                                                  m_editorWidget->position() - basePosition);
+    if (!newProposal->hasItemsToPropose(prefix, reason))
+        return;
+
+    if (destroyCurrentContext)
+        destroyContext();
 
     clearAbortedPosition();
     m_proposal.reset(proposalCandidate.take());
@@ -325,9 +339,7 @@ void CodeAssistantPrivate::displayProposal(IAssistProposal *newProposal, AssistR
     m_proposalWidget->setModel(m_proposal->model());
     m_proposalWidget->setDisplayRect(m_editorWidget->cursorRect(basePosition));
     m_proposalWidget->setIsSynchronized(!m_receivedContentWhileWaiting);
-    m_proposalWidget->showProposal(m_editorWidget->textAt(
-                                       basePosition,
-                                       m_editorWidget->position() - basePosition));
+    m_proposalWidget->showProposal(prefix);
 }
 
 void CodeAssistantPrivate::processProposalItem(AssistProposalItemInterface *proposalItem)
@@ -406,6 +418,8 @@ void CodeAssistantPrivate::notifyChange()
             m_proposalWidget->updateProposal(
                 m_editorWidget->textAt(m_proposal->basePosition(),
                                      m_editorWidget->position() - m_proposal->basePosition()));
+            if (m_proposal->isFragile())
+                startAutomaticProposalTimer();
         }
     }
 }
@@ -438,7 +452,7 @@ void CodeAssistantPrivate::startAutomaticProposalTimer()
 
 void CodeAssistantPrivate::automaticProposalTimeout()
 {
-    if (isWaitingForProposal() || isDisplayingProposal())
+    if (isWaitingForProposal() || (isDisplayingProposal() && !m_proposal->isFragile()))
         return;
 
     requestProposal(IdleEditor, Completion);
diff --git a/src/plugins/texteditor/codeassist/genericproposal.cpp b/src/plugins/texteditor/codeassist/genericproposal.cpp
index e8e19f1536..7d0105319c 100644
--- a/src/plugins/texteditor/codeassist/genericproposal.cpp
+++ b/src/plugins/texteditor/codeassist/genericproposal.cpp
@@ -49,6 +49,16 @@ bool GenericProposal::isFragile() const
     return false;
 }
 
+bool GenericProposal::hasItemsToPropose(const QString &prefix, AssistReason reason) const
+{
+    if (!prefix.isEmpty()) {
+        m_model->filter(prefix);
+        m_model->setPrefilterPrefix(prefix);
+    }
+
+    return m_model->hasItemsToPropose(prefix, reason);
+}
+
 IAssistProposalModel *GenericProposal::model() const
 {
     return m_model;
diff --git a/src/plugins/texteditor/codeassist/genericproposal.h b/src/plugins/texteditor/codeassist/genericproposal.h
index 19c743dbdb..385f9978df 100644
--- a/src/plugins/texteditor/codeassist/genericproposal.h
+++ b/src/plugins/texteditor/codeassist/genericproposal.h
@@ -41,6 +41,7 @@ public:
     ~GenericProposal();
 
     bool isFragile() const override;
+    bool hasItemsToPropose(const QString &prefix, AssistReason reason) const override;
     IAssistProposalModel *model() const override;
     IAssistProposalWidget *createWidget() const override;
 
diff --git a/src/plugins/texteditor/codeassist/genericproposalmodel.cpp b/src/plugins/texteditor/codeassist/genericproposalmodel.cpp
index 1afd0b8451..34ed001823 100644
--- a/src/plugins/texteditor/codeassist/genericproposalmodel.cpp
+++ b/src/plugins/texteditor/codeassist/genericproposalmodel.cpp
@@ -145,8 +145,65 @@ void GenericProposalModel::loadContent(const QList<AssistProposalItemInterface *
         m_idByText.insert(m_originalItems.at(i)->text(), i);
 }
 
+bool GenericProposalModel::hasItemsToPropose(const QString &prefix, AssistReason reason) const
+{
+    return size() != 0 && (keepPerfectMatch(reason) || !isPerfectMatch(prefix));
+}
+
+static QString cleanText(const QString &original)
+{
+    QString clean = original;
+    int ignore = 0;
+    for (int i = clean.length() - 1; i >= 0; --i, ++ignore) {
+        const QChar &c = clean.at(i);
+        if (c.isLetterOrNumber() || c == QLatin1Char('_')
+                || c.isHighSurrogate() || c.isLowSurrogate()) {
+            break;
+        }
+    }
+    if (ignore)
+        clean.chop(ignore);
+    return clean;
+}
+
+bool GenericProposalModel::isPerfectMatch(const QString &prefix) const
+{
+    if (prefix.isEmpty())
+        return false;
+
+    for (int i = 0; i < size(); ++i) {
+        const QString &current = cleanText(text(i));
+        if (!current.isEmpty()) {
+            CaseSensitivity cs = TextEditorSettings::completionSettings().m_caseSensitivity;
+            if (cs == TextEditor::CaseSensitive) {
+                if (prefix == current)
+                    return true;
+            } else if (cs == TextEditor::CaseInsensitive) {
+                if (prefix.compare(current, Qt::CaseInsensitive) == 0)
+                    return true;
+            } else if (cs == TextEditor::FirstLetterCaseSensitive) {
+                if (prefix.at(0) == current.at(0)
+                        && prefix.midRef(1).compare(current.midRef(1), Qt::CaseInsensitive) == 0)
+                    return true;
+            }
+        }
+    }
+    return false;
+}
+
+bool GenericProposalModel::isPrefiltered(const QString &prefix) const
+{
+    return !m_prefilterPrefix.isEmpty() && prefix == m_prefilterPrefix;
+}
+
+void GenericProposalModel::setPrefilterPrefix(const QString &prefix)
+{
+    m_prefilterPrefix = prefix;
+}
+
 void GenericProposalModel::reset()
 {
+    m_prefilterPrefix.clear();
     m_currentItems = m_originalItems;
 }
 
diff --git a/src/plugins/texteditor/codeassist/genericproposalmodel.h b/src/plugins/texteditor/codeassist/genericproposalmodel.h
index d3ff31fb6f..538ed81712 100644
--- a/src/plugins/texteditor/codeassist/genericproposalmodel.h
+++ b/src/plugins/texteditor/codeassist/genericproposalmodel.h
@@ -65,11 +65,18 @@ public:
 
     void loadContent(const QList<AssistProposalItemInterface *> &items);
 
+    bool isPerfectMatch(const QString &prefix) const;
+    bool hasItemsToPropose(const QString &prefix, AssistReason reason) const;
+
+    bool isPrefiltered(const QString &prefix) const;
+    void setPrefilterPrefix(const QString &prefix);
+
 protected:
     QList<AssistProposalItemInterface *> m_currentItems;
 
 private:
     QHash<QString, int> m_idByText;
     QList<AssistProposalItemInterface *> m_originalItems;
+    QString m_prefilterPrefix;
 };
 } // TextEditor
diff --git a/src/plugins/texteditor/codeassist/genericproposalwidget.cpp b/src/plugins/texteditor/codeassist/genericproposalwidget.cpp
index 1ce01ffa18..cdeb6638df 100644
--- a/src/plugins/texteditor/codeassist/genericproposalwidget.cpp
+++ b/src/plugins/texteditor/codeassist/genericproposalwidget.cpp
@@ -54,47 +54,6 @@ using namespace Utils;
 
 namespace TextEditor {
 
-static QString cleanText(const QString &original)
-{
-    QString clean = original;
-    int ignore = 0;
-    for (int i = clean.length() - 1; i >= 0; --i, ++ignore) {
-        const QChar &c = clean.at(i);
-        if (c.isLetterOrNumber() || c == QLatin1Char('_')
-                || c.isHighSurrogate() || c.isLowSurrogate()) {
-            break;
-        }
-    }
-    if (ignore)
-        clean.chop(ignore);
-    return clean;
-}
-
-static bool isPerfectMatch(const QString &prefix, const GenericProposalModel *model)
-{
-    if (prefix.isEmpty())
-        return false;
-
-    for (int i = 0; i < model->size(); ++i) {
-        const QString &current = cleanText(model->text(i));
-        if (!current.isEmpty()) {
-            CaseSensitivity cs = TextEditorSettings::completionSettings().m_caseSensitivity;
-            if (cs == TextEditor::CaseSensitive) {
-                if (prefix == current)
-                    return true;
-            } else if (cs == TextEditor::CaseInsensitive) {
-                if (prefix.compare(current, Qt::CaseInsensitive) == 0)
-                    return true;
-            } else if (cs == TextEditor::FirstLetterCaseSensitive) {
-                if (prefix.at(0) == current.at(0)
-                        && prefix.midRef(1).compare(current.midRef(1), Qt::CaseInsensitive) == 0)
-                    return true;
-            }
-        }
-    }
-    return false;
-}
-
 // ------------
 // ModelAdapter
 // ------------
@@ -442,12 +401,12 @@ bool GenericProposalWidget::updateAndCheck(const QString &prefix)
                 d->m_model->persistentId(d->m_completionListView->currentIndex().row());
 
     // Filter, sort, etc.
-    d->m_model->reset();
-    if (!prefix.isEmpty())
-        d->m_model->filter(prefix);
-    if (d->m_model->size() == 0
-            || (!d->m_model->keepPerfectMatch(d->m_reason)
-                && isPerfectMatch(prefix, d->m_model))) {
+    if (!d->m_model->isPrefiltered(prefix)) {
+        d->m_model->reset();
+        if (!prefix.isEmpty())
+            d->m_model->filter(prefix);
+    }
+    if (!d->m_model->hasItemsToPropose(prefix, d->m_reason)) {
         d->m_completionListView->reset();
         abort();
         return false;
diff --git a/src/plugins/texteditor/codeassist/iassistproposal.h b/src/plugins/texteditor/codeassist/iassistproposal.h
index 9a6332808c..732fe9a468 100644
--- a/src/plugins/texteditor/codeassist/iassistproposal.h
+++ b/src/plugins/texteditor/codeassist/iassistproposal.h
@@ -25,6 +25,8 @@
 
 #pragma once
 
+#include "assistenums.h"
+
 #include <texteditor/texteditor_global.h>
 
 namespace TextEditor {
@@ -40,6 +42,7 @@ public:
     virtual ~IAssistProposal();
 
     int basePosition() const;
+    virtual bool hasItemsToPropose(const QString &, AssistReason) const { return true; }
     virtual bool isFragile() const = 0;
     virtual bool isCorrective(TextEditorWidget *editorWidget) const;
     virtual void makeCorrection(TextEditorWidget *editorWidget);