From 2a936a75748c8341b4f35cfb189f53bce896f338 Mon Sep 17 00:00:00 2001
From: Avery Pennarun <apenwarr@gmail.com>
Date: Sat, 3 Nov 2018 03:36:13 -0400
Subject: [PATCH] Print a nicer error message when asked to build an empty
 string ('').

This happens sometimes, for example, if you do
	whatever | while read x; do
		redo-ifchange "$x"
	done
and the input contains blank lines.

We could ignore the request for blankness, but it seems like that
situation might indicate a more serious bug in your parser, so it's
probably better to just abort with a meaningful error.
---
 builder.py       | 4 ++++
 redo-ifcreate.py | 3 +++
 redo-whichdo.py  | 4 ++++
 state.py         | 3 +--
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/builder.py b/builder.py
index 0681a54..15f435c 100644
--- a/builder.py
+++ b/builder.py
@@ -282,6 +282,10 @@ def main(targets, shouldbuildfunc):
     seen = {}
     lock = None
     for t in targets:
+        if not t:
+            err('cannot build the empty target ("").\n')
+            retcode[0] = 204
+            break
         assert(state.is_flushed())
         if t in seen:
             continue
diff --git a/redo-ifcreate.py b/redo-ifcreate.py
index 08a9cd4..b17acae 100755
--- a/redo-ifcreate.py
+++ b/redo-ifcreate.py
@@ -9,6 +9,9 @@ try:
                       os.path.join(vars.PWD, vars.TARGET))
     f = state.File(name=me)
     for t in sys.argv[1:]:
+        if not t:
+            err('cannot build the empty target ("").\n')
+            sys.exit(204)
         if os.path.exists(t):
             err('redo-ifcreate: error: %r already exists\n' % t)
             sys.exit(1)
diff --git a/redo-whichdo.py b/redo-whichdo.py
index bece6d1..c692e98 100755
--- a/redo-whichdo.py
+++ b/redo-whichdo.py
@@ -12,6 +12,10 @@ if len(sys.argv[1:]) != 1:
     sys.exit(1)
 
 want = sys.argv[1]
+if not want:
+    err('cannot build the empty target ("").\n')
+    sys.exit(204)
+
 abswant = os.path.abspath(want)
 for dodir,dofile,basedir,basename,ext in paths.possible_do_files(abswant):
     dopath = os.path.join('/', dodir, dofile)
diff --git a/state.py b/state.py
index dd490db..c857ebf 100644
--- a/state.py
+++ b/state.py
@@ -189,8 +189,7 @@ class File(object):
         row = d.execute(q, l).fetchone()
         if not row:
             if not name:
-                raise Exception('File with id=%r not found and '
-                                'name not given' % id)
+                raise Exception('No file with id=%r name=%r' % (id, name))
             try:
                 _write('insert into Files (name) values (?)', [name])
             except sqlite3.IntegrityError: