From 4e30ce160e7e7ea4e2f7801d15b1659f19a27177 Mon Sep 17 00:00:00 2001
From: hjk <hjk@qt.io>
Date: Tue, 25 May 2021 15:25:37 +0200
Subject: [PATCH] Utils: Start collecting environment changes instead of full
 environments

We have a couple of cases where classes need to modify environments but
have only the ability to provide complete environments without actually
knowing the full context. Starting with systemEnvironment usually works
so far, but breaks down in cases of e.g. containerized builds.

This patch here introduces the ability to collect changes to
environments, and postpones creating a full environment until the
context is clear.

As introductory example use BaseQtVersion::qmakeRunEnvironment

Change-Id: Id23c0aa80fc95b0a8a01f8e3a87adc9b1a57002a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
---
 src/libs/utils/environment.cpp | 31 +++++++++++++++++++++++++++++++
 src/libs/utils/environment.h   | 20 ++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/src/libs/utils/environment.cpp b/src/libs/utils/environment.cpp
index e02a407dbc9..fe1769daffa 100644
--- a/src/libs/utils/environment.cpp
+++ b/src/libs/utils/environment.cpp
@@ -401,4 +401,35 @@ optional<EnvironmentProvider> EnvironmentProvider::provider(const QByteArray &id
     return nullopt;
 }
 
+void EnvironmentChange::addSetValue(const QString &key, const QString &value)
+{
+    m_changeItems.append([key, value](Environment &env) { env.set(key, value); });
+}
+
+void EnvironmentChange::addUnsetValue(const QString &key)
+{
+    m_changeItems.append([key](Environment &env) { env.unset(key); });
+}
+
+void EnvironmentChange::addPrependToPath(const QString &value)
+{
+    m_changeItems.append([value](Environment &env) { env.prependOrSetPath(value); });
+}
+
+void EnvironmentChange::addAppendToPath(const QString &value)
+{
+    m_changeItems.append([value](Environment &env) { env.appendOrSetPath(value); });
+}
+
+void EnvironmentChange::addModify(const NameValueItems &items)
+{
+    m_changeItems.append([items](Environment &env) { env.modify(items); });
+}
+
+void EnvironmentChange::applyToEnvironment(Environment &env) const
+{
+    for (const Item &item : m_changeItems)
+        item(env);
+}
+
 } // namespace Utils
diff --git a/src/libs/utils/environment.h b/src/libs/utils/environment.h
index 75e7aeb4aa9..0ed2d9b613c 100644
--- a/src/libs/utils/environment.h
+++ b/src/libs/utils/environment.h
@@ -86,6 +86,26 @@ private:
                                       QSet<FilePath> &alreadyChecked);
 };
 
+class QTCREATOR_UTILS_EXPORT EnvironmentChange final
+{
+public:
+    using Item = std::function<void(Environment &)>;
+
+    EnvironmentChange() = default;
+
+    void applyToEnvironment(Environment &) const;
+
+    void addSetValue(const QString &key, const QString &value);
+    void addUnsetValue(const QString &key);
+    void addPrependToPath(const QString &value);
+    void addAppendToPath(const QString &value);
+    void addModify(const NameValueItems &items);
+    void addChange(const Item &item) { m_changeItems.append(item); }
+
+private:
+    QList<Item> m_changeItems;
+};
+
 class QTCREATOR_UTILS_EXPORT EnvironmentProvider
 {
 public: