From d69645bc124ce675326b0778d261962791855b38 Mon Sep 17 00:00:00 2001 From: Todd Lyons Date: Thu, 4 Sep 2014 11:20:31 -0700 Subject: Bug 1518: fix description of condition processing The description in the first commit was completely wrong. Thanks to Phil for setting me straight and seeding me with the correct verbage. --- doc/doc-docbook/spec.xfpt | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) (limited to 'doc') diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index ffe153ae9..2a52666f6 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -16828,15 +16828,18 @@ of the other precondition options are common special cases that could in fact be specified using &%condition%&. .new -When originally designed, Exim's ACL system enforced very strict parsing -of the &%condition%& expansion everywhere it was being processed. -Through the 4.7x release cycle, the &%condition%& processing while in a -router became more loose, internally adopting the use of &%bool_lax%& -instead of the more rigid &%bool%&. This is best illustrated in an -example: +Historical note: We have &%condition%& on ACLs and on Routers. Routers +are far older, and use one set of semantics. ACLs are newer and when +they were created, the ACL &%condition%& process was given far stricter +parse semantics. The &%bool{}&% expansion condition uses the same rules as +ACLs. The &%bool_lax{}%& expansion condition uses the same rules as +Routers. More pointedly, the &%bool_lax{}%& was written to match the existing +Router rules processing behavior. + +This is best illustrated in an example: .code -# This used to fail with a syntax error, now it -# treats any extra characters as a string +# If used in an ACL condition will fail with a syntax error, but +# in a router condition any extra characters are treated as a string $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}' true {yes} {no}} @@ -16854,10 +16857,16 @@ resulted in the null output (indicating false) with the string &" {yes} {no}}"& appended to it. In fact you can put excess forward braces in too. In the router -&%condition%&, Exim's ACL parser only looks for &"{"& symbols when they +&%condition%&, Exim's parser only looks for &"{"& symbols when they mean something, like after a &"$"& or when required as part of a conditional. But otherwise &"{"& and &"}"& are treated as ordinary string characters. + +Thus, in a Router, the above expansion strings will both always evaluate +true, as the result of expansion is a non-empty string which doesn't +match an explicit false value. This can be tricky to debug. By +contrast, in an ACL either of those strings will always result in an +expansion error because the result doesn't look sufficiently boolean. .wen -- cgit v1.2.3