OS: Add `unset_environment`, better validate input

Instead of returning an undocumented boolean error code, we do the
validation checks that should ensure a successful result.

Based on:
- https://linux.die.net/man/3/setenv
- https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-setenvironmentvariable

2 files changed, 13 insertions, 3 deletions

diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index b3831573cf..130c5f7b97 100644
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -1166,8 +1166,17 @@ String OS_Windows::get_environment(const String &p_var) const {
 	return "";
 }
 
-bool OS_Windows::set_environment(const String &p_var, const String &p_value) const {
-	return (bool)SetEnvironmentVariableW((LPCWSTR)(p_var.utf16().get_data()), (LPCWSTR)(p_value.utf16().get_data()));
+void OS_Windows::set_environment(const String &p_var, const String &p_value) const {
+	ERR_FAIL_COND_MSG(p_var.is_empty() || p_var.contains("="), vformat("Invalid environment variable name '%s', cannot be empty or include '='.", p_var));
+	Char16String var = p_var.utf16();
+	Char16String value = p_value.utf16();
+	ERR_FAIL_COND_MSG(var.length() + value.length() + 2 > 32767, vformat("Invalid definition for environment variable '%s', cannot exceed 32767 characters.", p_var));
+	SetEnvironmentVariableW((LPCWSTR)(var.get_data()), (LPCWSTR)(value.get_data()));
+}
+
+void OS_Windows::unset_environment(const String &p_var) const {
+	ERR_FAIL_COND_MSG(p_var.is_empty() || p_var.contains("="), vformat("Invalid environment variable name '%s', cannot be empty or include '='.", p_var));
+	SetEnvironmentVariableW((LPCWSTR)(p_var.utf16().get_data()), nullptr); // Null to delete.
 }
 
 String OS_Windows::get_stdin_string() {
diff --git a/platform/windows/os_windows.h b/platform/windows/os_windows.h
index c33e0f6740..05110c2614 100644
--- a/platform/windows/os_windows.h
+++ b/platform/windows/os_windows.h
@@ -186,7 +186,8 @@ public:
 
 	virtual bool has_environment(const String &p_var) const override;
 	virtual String get_environment(const String &p_var) const override;
-	virtual bool set_environment(const String &p_var, const String &p_value) const override;
+	virtual void set_environment(const String &p_var, const String &p_value) const override;
+	virtual void unset_environment(const String &p_var) const override;
 
 	virtual Vector<String> get_system_fonts() const override;
 	virtual String get_system_font_path(const String &p_font_name, int p_weight = 400, int p_stretch = 100, bool p_italic = false) const override;