scanner: Add various static debug hooks in GI_SCANNER_DEBUG

For backwards compat, keep the presence of the environment
variable at all to mean "exception".

Also start a HACKING file.

1 files changed, 21 insertions, 0 deletions

diff --git a/giscanner/utils.py b/giscanner/utils.py
index dba958ef..2263b8cd 100644
--- a/giscanner/utils.py
+++ b/giscanner/utils.py
@@ -22,6 +22,27 @@ import re
 import os
 import subprocess
 
+_debugflags = None
+def have_debug_flag(flag):
+    """Check for whether a specific debugging feature is enabled.
+Well-known flags:
+ * start: Drop into debugger just after processing arguments
+ * exception: Drop into debugger on fatalexception
+ * warning: Drop into debugger on warning
+ * posttrans: Drop into debugger just before introspectable pass
+"""
+    global _debugflags
+    if _debugflags is None:
+        _debugflags = os.environ.get('GI_SCANNER_DEBUG', '').split(',')
+        if '' in _debugflags:
+            _debugflags.remove('')
+    return flag in _debugflags
+
+def break_on_debug_flag(flag):
+    if have_debug_flag(flag):
+        import pdb
+        pdb.set_trace()
+
 # Copied from h2defs.py
 _upperstr_pat1 = re.compile(r'([^A-Z])([A-Z])')
 _upperstr_pat2 = re.compile(r'([A-Z][A-Z])([A-Z][0-9a-z])')