Review parser Makefile (#2765)

* parser: Fail gracefully if a nonexistent file is passed on the command line

Before, if a nonexistent file was passed to LoadFileText(), it would
return NULL, and the parser would happily dereference it.

* parser: Refactor Makefile and update the path to easings.h (now reasings.h)

Before, the `make all` target would simply segfault, see 0a679d79
Now, if a file in the `make all` target doesn't exist, make will write
an error.

Individual API files can be generated likeso, provided the header file
the target depends on exists:

FORMAT=JSON EXTENSION=json make raygui_api.json

In order for the `make all` target to succeed, raygui.h, physac.h and
rmem.h need to be added to the correct directory.

parser/Makefile

@@ -1,28 +1,50 @@
 EXTENSION?=txt
 FORMAT?=DEFAULT
+.PHONY: all parse clean raylib_api
 
-raylib_api:
-	cc raylib_parser.c -o raylib_parser
-	./raylib_parser -i ../src/raylib.h -o raylib_api.txt -f DEFAULT -d RLAPI
-	./raylib_parser -i ../src/raylib.h -o raylib_api.json -f JSON -d RLAPI
-	./raylib_parser -i ../src/raylib.h -o raylib_api.xml -f XML -d RLAPI
-	./raylib_parser -i ../src/raylib.h -o raylib_api.lua -f LUA -d RLAPI
 
-all:
+raylib_parser: raylib_parser.c
 	cc raylib_parser.c -o raylib_parser
-	FORMAT=DEFAULT EXTENSION=txt $(MAKE) parse
-	FORMAT=JSON EXTENSION=json $(MAKE) parse
-	FORMAT=XML EXTENSION=xml $(MAKE) parse
-	FORMAT=LUA EXTENSION=lua $(MAKE) parse
 
-parse:
+raylib_api: ../src/raylib.h raylib_parser
+	FORMAT=DEFAULT EXTENSION=txt $(MAKE) raylib_api.txt
+	FORMAT=JSON EXTENSION=json $(MAKE) raylib_api.json
+	FORMAT=XML EXTENSION=xml $(MAKE) raylib_api.xml
+	FORMAT=LUA EXTENSION=lua $(MAKE) raylib_api.lua
+
+raylib_api.$(EXTENSION): ../src/raylib.h raylib_parser
 	./raylib_parser -i ../src/raylib.h -o raylib_api.$(EXTENSION) -f $(FORMAT) -d RLAPI
+
+raymath_api.$(EXTENSION): ../src/raymath.h raylib_parser
 	./raylib_parser -i ../src/raymath.h -o raymath_api.$(EXTENSION) -f $(FORMAT) -d RMAPI
+
+rlgl_api.$(EXTENSION): ../src/rlgl.h raylib_parser
 	./raylib_parser -i ../src/rlgl.h -o rlgl_api.$(EXTENSION) -f $(FORMAT) -d RLAPI -t "RLGL IMPLEMENTATION"
-	./raylib_parser -i ../src/easings.h -o easings_api.$(EXTENSION) -f $(FORMAT) -d EASEDEF
-	./raylib_parser -i ../src/rmem.h -o rmem_api.$(EXTENSION) -f $(FORMAT) -d RMEMAPI -t "RMEM IMPLEMENTATION"
+
+reasings_api.$(EXTENSION): ../examples/others/reasings.h raylib_parser
+	./raylib_parser -i ../examples/others/reasings.h -o reasings_api.$(EXTENSION) -f $(FORMAT) -d EASEDEF
+
+rmem_api.$(EXTENSION): ../rmem.h raylib_parser
+	./raylib_parser -i ../rmem.h -o rmem_api.$(EXTENSION) -f $(FORMAT) -d RMEMAPI -t "RMEM IMPLEMENTATION"
+
+physac_api.$(EXTENSION): ../physac.h raylib_parser
 	./raylib_parser -i ../physac.h -o physac_api.$(EXTENSION) -f $(FORMAT) -d PHYSACDEF -t "PHYSAC IMPLEMENTATION"
+
+raygui_api.$(EXTENSION): ../raygui.h raylib_parser
 	./raylib_parser -i ../raygui.h -o raygui_api.$(EXTENSION) -f $(FORMAT) -d RAYGUIAPI -t "RAYGUI IMPLEMENTATION"
 
+parse: raylib_api.$(EXTENSION) raymath_api.$(EXTENSION) rlgl_api.$(EXTENSION) rmem_api.$(EXTENSION) physac_api.$(EXTENSION) raygui_api.$(EXTENSION)
+
+
+# `make parse` (and therefore `make all) requires
+# rmem.h, physac.h and raygui.h to exist in the correct directory
+# API files for individual headers can be created likeso, provided the relevant header exists:
+#     FORMAT=JSON EXTENSION=json make raygui_api.json
+all: raylib_parser
+	FORMAT=DEFAULT EXTENSION=txt $(MAKE) parse
+	FORMAT=JSON EXTENSION=json $(MAKE) parse
+	FORMAT=XML EXTENSION=xml $(MAKE) parse
+	FORMAT=LUA EXTENSION=lua $(MAKE) parse
+
 clean:
 	rm -f raylib_parser *.json *.txt *.xml *.lua

parser/raylib_parser.c

@@ -207,6 +207,12 @@ int main(int argc, char* argv[])
     int length = 0;
     char *buffer = LoadFileText(inFileName, &length);
 
+    if (buffer == NULL)
+    {
+	    printf("Could not read input file: %s\n", inFileName);
+	    return 1;
+    }
+
     // Preprocess buffer to get separate lines
     // NOTE: GetTextLines() also removes leading spaces/tabs
     int linesCount = 0;