From 89839bc45380d9a3b6aed3750f8ea64b31bf5f27 Mon Sep 17 00:00:00 2001
From: Zhang Yunjun <yunjunz@users.noreply.github.com>
Date: Thu, 21 May 2020 22:11:18 -0700
Subject: [PATCH] extractCommonValidRegion: check stack/*.xml file existance

Otherwise, if 'stack' folder exists but is empty, the script will return ERROR as below:

```
/net/kraken/nobak/zyunjun/TonopahSenAT64/stack  already exists.
Replacing master with existing stack.
updating the valid overlap region of:
/net/kraken/nobak/zyunjun/TonopahSenAT64/stack
******************
swath:  1
Traceback (most recent call last):
  File "/home/zyunjun/tools/isce2/contrib/stack/topsStack/extractCommonValidRegion.py", line 109, in <module>
    main()
  File "/home/zyunjun/tools/isce2/contrib/stack/topsStack/extractCommonValidRegion.py", line 95, in main
    topMaster = ut.loadProduct(os.path.join(inps.master , 'IW{0}.xml'.format(swath)))
  File "/home/zyunjun/tools/isce2/contrib/stack/topsStack/s1a_isce_utils.py", line 26, in loadProduct
    obj = pm.loadProduct(xmlname)
  File "/net/kraken/home1/geomod/apps/rhel7/isce2-github/isce/components/iscesys/Component/ProductManager.py", line 25, in loadProduct
    self.load(filename)
  File "/net/kraken/home1/geomod/apps/rhel7/isce2-github/isce/components/iscesys/Component/Configurable.py", line 1407, in load
    tmpProp, tmpFact, tmpMisc = FP.parse(filename)
  File "/net/kraken/home1/geomod/apps/rhel7/isce2-github/isce/components/iscesys/Parsers/XmlParser.py", line 41, in parse
    root = ET.parse(filename)
  File "/net/kraken/home1/geomod/apps/anaconda3/lib/python3.7/xml/etree/ElementTree.py", line 1197, in parse
    tree.parse(source, parser)
  File "/net/kraken/home1/geomod/apps/anaconda3/lib/python3.7/xml/etree/ElementTree.py", line 587, in parse
    source = open(source, "rb")
FileNotFoundError: [Errno 2] No such file or directory: '/net/kraken/nobak/zyunjun/TonopahSenAT64/stack/IW1.xml'
```
---
 .../stack/topsStack/extractCommonValidRegion.py   | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/contrib/stack/topsStack/extractCommonValidRegion.py b/contrib/stack/topsStack/extractCommonValidRegion.py
index 7405521..baa5606 100755
--- a/contrib/stack/topsStack/extractCommonValidRegion.py
+++ b/contrib/stack/topsStack/extractCommonValidRegion.py
@@ -2,16 +2,17 @@
 
 #Author: Heresh Fattahi
 
+import os
+import argparse
+import glob
+import numpy as np
+import gdal
 import isce
 import isceobj
-import numpy as np
-import argparse
-import os
 from isceobj.Sensor.TOPS import createTOPSSwathSLCProduct
 from mroipac.correlation.correlation import Correlation
 import s1a_isce_utils as ut
-import gdal
-import glob
+
 
 def createParser():
     parser = argparse.ArgumentParser( description='Extract valid overlap region for the stack')
@@ -76,7 +77,7 @@ def main(iargs=None):
     if not os.path.exists(stackDir):
         print('creating ', stackDir)
         os.makedirs(stackDir)
-    else:
+    elif len(glob.glob(os.path.join(stackDir, '*.xml'))) > 0:
         print(stackDir , ' already exists.')
         print('Replacing reference with existing stack.')
         inps.reference = stackDir
@@ -139,7 +140,7 @@ swath = ut.loadProduct(os.path.join(slcPath , 'IW{0}.xml'.format(2)))
 
 tref = swath.sensingStart
 rref = swath.bursts[0].startingRange
-dt = swath.bursts[0].azimuthTimeInterval 
+dt = swath.bursts[0].azimuthTimeInterval
 dr = swath.bursts[0].rangePixelSize