Avoid creating constants and macros in the global namespace

[alranel]

This library defines some constants in the global namespace, such as the following ones:

ArduinoIoTCloud/src/ArduinoIoTCloud.h

Lines 51 to 56 in 451d57d

	typedef enum
	{
	READ = 0x01,
	WRITE = 0x02,
	READWRITE = READ | WRITE
	} permissionType;

This generates errors whenever they are also defined by other libraries, preventing their coexistence. For instance, the ArduinoBLE library defines both READ and WRITE (not anymore, constants were renamed in ArduinoBLE) and in general it is very likely to find constants named like this.

It would be nice to avoid polluting the global namespace, obviously in a retrocompatible way...

[per1234]

Another example of this practice resulting in name collisions: #280

[alranel]

We also have this problem with macros such as the ones defined here:

ArduinoIoTCloud/src/property/Property.h

Lines 50 to 52 in 925922b

	#define appendAttributesToCloud() appendAttributesToCloudReal(CborEncoder *encoder)
	#define appendAttribute(x) appendAttributeReal(x, getAttributeName(#x, '.'), encoder)
	#define setAttribute(x) setAttributeReal(x, getAttributeName(#x, '.'))

setAttributes() is a very common function name, and in fact this prevents using the very popular TFT_eSPI library with IoT Cloud as compilation fails as follows:

In file included from /tmp/936788285/TTGO_oct06a/TTGO_oct06a.ino:19: /home/builder/opt/libraries/latest/tft_espi_2_4_72/TFT_eSPI.h:728:54: error: macro "setAttribute" passed 2 arguments, but takes just 1 void setAttribute(uint8_t id = 0, uint8_t a = 0); // Set attribute value ^ Error during build: exit status 1
In file included from /tmp/936788285/TTGO_oct06a/TTGO_oct06a.ino:19: /home/builder/opt/libraries/latest/tft_espi_2_4_72/TFT_eSPI.h:728:54: error: macro "setAttribute" passed 2 arguments, but takes just 1 void setAttribute(uint8_t id = 0, uint8_t a = 0); // Set attribute value ^ Error during build: exit status 1

The workaround is to undef the symbol in the user sketch before including other libraries:

#undef setAttribute(x)
#include <TFT_eSPI.h>

However this library should be fixed to maximize its compatibility and avoid any overlap with other symbols in the global namespace.

[facchinm]

Since the macro is only being used internally inside the various Cloud* types, I suggest to undef at the end of all .h using it (https://github.com/arduino-libraries/ArduinoIoTCloud/search?q=setAttribute)
@pennam can you take a look?

[alranel]

@facchinm With that approach wouldn't you still override any existing macros created by other libraries imported before this one? Wouldn't it be better to switch to namespaced symbols such as proper functions, constexprs or even just prefixing the macros with AIOTC_?

[facchinm]

These symbols cannot be turned into proper functions due to stringification, but since they are not intended to be used by the end user we can safely prefix with AIOTC_ or similar

[pennam]

@alranel regarding READ, WRITE and READWRITE there is already an alternative in the library:

ArduinoIoTCloud/src/property/Property.h

Lines 130 to 132 in 9c6d5d7

	enum class Permission {
	Read, Write, ReadWrite
	};

The first step to remove READ, WRITE and READWRITE is to update the template used to generate the sketches in the cloud editor, but unfortunately even if we do so, removing them from the library will be a breaking change becase all "non-cloud" sketches will throw a compilation error.

/cc @eclipse1985