Fat FS: If can't allocate file, attempt defragmentation and try again

Author: gfwilliams

ChangeLog

@@ -17,6 +17,7 @@
             Bangle.js2: Calling Bangle.getPressure() while a conversion is in progress now returns the same promise (so it will complete as soon as pressure data is ready) rather than erroring
             Bangle.js2: Fix 2v22 regression where `E.showMenu({test:{}})` would display 'test:undefined'
             Fat FS: Added `r+` file open mode (and allow w+ to read)
+            Fat FS: If can't allocate file, attempt defragmentation and try again
 
      2v26 : nRF5x: ensure TIMER1_IRQHandler doesn't always wake idle loop up (fix #1900)
             Puck.js: On v2.1 ensure Puck.mag behaves like other variants - just returning the last reading (avoids glitches when used with Puck.magOn)

libs/filesystem/jswrap_file.c

@@ -253,6 +253,10 @@ static bool allocateJsFile(JsFile* file,FileMode mode, FileType type) {
   if (!parent) return false; // low memory
 
   JsVar *data = jsvNewFlatStringOfLength(sizeof(JsFileData));
+  if (!data) { // out of memory for flat string
+    jsvDefragment(); // defrag and try again in case it was a memory fragmentation issue
+    data = jsvNewFlatStringOfLength(sizeof(JsFileData));
+  }
   if (!data) { // out of memory for flat string
     jsErrorFlags |= JSERR_LOW_MEMORY; // flag this up as an issue
     jsvUnLock(parent);