MAINT: don't rewrite api headers unnecessarily

This would mess up automatic compile dependency determination.

3 files changed, 27 insertions, 23 deletions

diff --git a/numpy/core/code_generators/genapi.py b/numpy/core/code_generators/genapi.py
index a71ffefdd..c1e2d1fee 100644
--- a/numpy/core/code_generators/genapi.py
+++ b/numpy/core/code_generators/genapi.py
@@ -292,6 +292,20 @@ def should_rebuild(targets, source_files):
         return True
     return False
 
+def write_file(filename, data):
+    """
+    Write data to filename
+    Only write changed data to avoid updating timestamps unnecessarily
+    """
+    if os.path.exists(filename):
+        with open(filename) as f:
+            if data == f.read():
+                return
+
+    with open(filename, 'w') as fid:
+        fid.write(data)
+
+
 # Those *Api classes instances know how to output strings for the generated code
 class TypeApi(object):
     def __init__(self, name, index, ptr_cast, api_name):
diff --git a/numpy/core/code_generators/generate_numpy_api.py b/numpy/core/code_generators/generate_numpy_api.py
index d6d6ab21f..79d774a89 100644
--- a/numpy/core/code_generators/generate_numpy_api.py
+++ b/numpy/core/code_generators/generate_numpy_api.py
@@ -231,23 +231,18 @@ def do_generate_api(targets, sources):
         module_list.append(api_item.internal_define())
 
     # Write to header
-    fid = open(header_file, 'w')
     s = h_template % ('\n'.join(module_list), '\n'.join(extension_list))
-    fid.write(s)
-    fid.close()
+    genapi.write_file(header_file, s)
 
     # Write to c-code
-    fid = open(c_file, 'w')
     s = c_template % ',\n'.join(init_list)
-    fid.write(s)
-    fid.close()
+    genapi.write_file(c_file, s)
 
     # write to documentation
-    fid = open(doc_file, 'w')
-    fid.write(c_api_header)
+    s = c_api_header
     for func in numpyapi_list:
-        fid.write(func.to_ReST())
-        fid.write('\n\n')
-    fid.close()
+        s += func.to_ReST()
+        s += '\n\n'
+    genapi.write_file(doc_file, s)
 
     return targets
diff --git a/numpy/core/code_generators/generate_ufunc_api.py b/numpy/core/code_generators/generate_ufunc_api.py
index b6034bbe7..3bcf137f7 100644
--- a/numpy/core/code_generators/generate_ufunc_api.py
+++ b/numpy/core/code_generators/generate_ufunc_api.py
@@ -189,27 +189,22 @@ def do_generate_api(targets, sources):
         module_list.append(api_item.internal_define())
 
     # Write to header
-    fid = open(header_file, 'w')
     s = h_template % ('\n'.join(module_list), '\n'.join(extension_list))
-    fid.write(s)
-    fid.close()
+    genapi.write_file(header_file, s)
 
     # Write to c-code
-    fid = open(c_file, 'w')
     s = c_template % ',\n'.join(init_list)
-    fid.write(s)
-    fid.close()
+    genapi.write_file(c_file, s)
 
     # Write to documentation
-    fid = open(doc_file, 'w')
-    fid.write('''
+    s = '''
 =================
 NumPy Ufunc C-API
 =================
-''')
+'''
     for func in ufunc_api_list:
-        fid.write(func.to_ReST())
-        fid.write('\n\n')
-    fid.close()
+        s += func.to_ReST()
+        s += '\n\n'
+    genapi.write_file(doc_file, s)
 
     return targets