Utils: Add a way to provide fall-back entries in an environment

These are used if a (presumably fully-expanded) environment does
not have a value for a certain key. Currently this works only for
fully-known environments, but this can at least be delayed until
the environment is needed, not when it is set up.

Change-Id: I9baaa2d23002ddd574101741a91d5f872e6b0314
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/libs/utils/environment.cpp

@@ -494,6 +494,12 @@ void Environment::set(const QString &key, const QString &value, bool enabled)
                  std::tuple<QString, QString, bool>{key, value, enabled}});
 }
 
+void Environment::setFallback(const QString &key, const QString &value)
+{
+    addItem(Item{std::in_place_index_t<SetFallbackValue>(),
+                 std::tuple<QString, QString>{key, value}});
+}
+
 void Environment::unset(const QString &key)
 {
     addItem(Item{std::in_place_index_t<UnsetValue>(), key});
@@ -536,19 +542,33 @@ const NameValueDictionary &Environment::resolved() const
     if (m_dict.size() != 0)
         return m_dict;
 
+    m_fullDict = false;
     for (const Item &item : m_changeItems) {
         switch (item.index()) {
         case SetSystemEnvironment:
             m_dict = Environment::systemEnvironment().toDictionary();
+            m_fullDict = true;
             break;
         case SetFixedDictionary:
             m_dict = std::get<SetFixedDictionary>(item);
+            m_fullDict = true;
             break;
         case SetValue: {
             auto [key, value, enabled] = std::get<SetValue>(item);
             m_dict.set(key, value, enabled);
             break;
         }
+        case SetFallbackValue: {
+            auto [key, value] = std::get<SetFallbackValue>(item);
+            if (m_fullDict) {
+                if (m_dict.value(key).isEmpty())
+                    m_dict.set(key, value, true);
+            } else {
+                QTC_ASSERT(false, qDebug() << "operating on partial dictionary");
+                m_dict.set(key, value, true);
+            }
+            break;
+        }
         case UnsetValue:
             m_dict.unset(std::get<UnsetValue>(item));
             break;

src/libs/utils/environment.h

@@ -33,6 +33,7 @@ public:
     bool hasKey(const QString &key) const;
 
     void set(const QString &key, const QString &value, bool enabled = true);
+    void setFallback(const QString &key, const QString &value);
     void unset(const QString &key);
     void modify(const NameValueItems &items);
 
@@ -55,6 +56,7 @@ public:
     void appendToPath(const FilePaths &values);
 
     void setupEnglishOutput();
+    void setupSudoAskPass(const FilePath &askPass);
 
     FilePath searchInPath(const QString &executable,
                           const FilePaths &additionalDirs = FilePaths(),
@@ -95,22 +97,25 @@ public:
         SetSystemEnvironment,
         SetFixedDictionary,
         SetValue,
+        SetFallbackValue,
         UnsetValue,
         PrependOrSet,
         AppendOrSet,
         Modify,
-        SetupEnglishOutput,
+        SetupEnglishOutput
     };
 
     using Item = std::variant<
         std::monostate,                          // SetSystemEnvironment dummy
         NameValueDictionary,                     // SetFixedDictionary
         std::tuple<QString, QString, bool>,      // SetValue (key, value, enabled)
+        std::tuple<QString, QString>,            // SetFallbackValue (key, value)
         QString,                                 // UnsetValue (key)
         std::tuple<QString, QString, QString>,   // PrependOrSet (key, value, separator)
         std::tuple<QString, QString, QString>,   // AppendOrSet (key, value, separator)
         NameValueItems,                          // Modify
-        std::monostate                           // SetupEnglishOutput
+        std::monostate,                          // SetupEnglishOutput
+        FilePath                                 // SetupSudoAskPass (file path of qtc-askpass or ssh-askpass)
     >;
 
     void addItem(const Item &item);
@@ -122,6 +127,7 @@ public:
 private:
     mutable QList<Item> m_changeItems;
     mutable NameValueDictionary m_dict; // Latest resolved.
+    mutable bool m_fullDict = false;
 };
 
 using EnviromentChange = Environment;

src/plugins/projectexplorer/runcontrol.cpp

@@ -1069,11 +1069,9 @@ bool RunControl::showPromptToStopDialog(const QString &title,
 
 void RunControl::provideAskPassEntry(Environment &env)
 {
-    if (env.value("SUDO_ASKPASS").isEmpty()) {
+    const FilePath askpass = SshSettings::askpassFilePath();
-        const FilePath askpass = SshSettings::askpassFilePath();
+    if (askpass.exists())
-        if (askpass.exists())
+        env.setFallback("SUDO_ASKPASS", askpass.toUserOutput());
-            env.set("SUDO_ASKPASS", askpass.toUserOutput());
-    }
 }
 
 bool RunControlPrivate::isAllowedTransition(RunControlState from, RunControlState to)