do not ignore differently versioned self-provides

[apt.git] / doc / external-dependency-solver-protocol.txt

diff --git a/doc/external-dependency-solver-protocol.txt b/doc/external-dependency-solver-protocol.txt
index 7a124d8f92974127475ffb8e039a207f928a4744..5757991a835af14e590cb83d10710a70a58d8d0f 100644 (file)
--- a/doc/external-dependency-solver-protocol.txt
+++ b/doc/external-dependency-solver-protocol.txt
@@ -1,10 +1,18 @@
-# APT External Dependency Solver Protocol (EDSP) - version 0.4
+# APT External Dependency Solver Protocol (EDSP) - version 0.5
 
 This document describes the communication protocol between APT and
 external dependency solvers. The protocol is called APT EDSP, for "APT
 External Dependency Solver Protocol".
 
 
+## Terminology
+
+In the following we use the term **architecture qualified package name**
+(or *arch-qualified package names* for short) to refer to package
+identifiers of the form "package:arch" where "package" is a package name
+and "arch" a dpkg architecture.
+
+
 ## Components
 
 - **APT**: we know this one.
@@ -62,6 +70,7 @@ configuration documentation for more, and more up to date, information.
 - **Dir::Bin::Solvers**: absolute path of the directory where to look for
   external solvers. Defaults to `/usr/lib/apt/solvers`.
 
+
 ## Protocol
 
 When configured to use an external solver, APT will resort to it to
@@ -110,23 +119,31 @@ Within a dependency solving scenario, a request represents the action on
 installed packages requested by the user.
 
 A request is a single Deb 822 stanza opened by a mandatory Request field
-and followed by a mixture of action and preference fields.
+and followed by a mixture of action, preference, and global
+configuration fields.
 
 The value of the **Request:** field is a string describing the EDSP
 protocol which will be used to communicate. At present, the string must
-be `EDSP 0.4`.
+be `EDSP 0.5`. Request fields are mainly used to identify the beginning
+of a request stanza; their actual values are otherwise not used by the
+EDSP protocol.
+
+The following **configuration fields** are supported in request stanzas:
 
-a unique request identifier, such as an
-UUID. Request fields are mainly used to identify the beginning of a
-request stanza; their actual values are otherwise not used by the EDSP
-protocol.
+- **Architecture:** (mandatory) The name of the *native* architecture on
+  the user machine (see also: `dpkg --print-architecture`)
+
+- **Architectures:** (optional, defaults to the native architecture) A
+  space separated list of *all* architectures known to APT (this is
+  roughly equivalent to the union of `dpkg --print-architecture` and
+  `dpkg --print-foreign-architectures`)
 
 The following **action fields** are supported in request stanzas:
 
 - **Install:** (optional, defaults to the empty string) A space
-  separated list of package names, with *no version attached*, to
-  install. This field denotes a list of packages that the user wants to
-  install, usually via an APT `install` request.
+  separated list of arch-qualified package names, with *no version
+  attached*, to install. This field denotes a list of packages that the
+  user wants to install, usually via an APT `install` request.
 
 - **Remove:** (optional, defaults to the empty string) Same syntax of
   Install. This field denotes a list of packages that the user wants to
@@ -193,7 +210,7 @@ field. The following fields are supported in package stanzas:
 - **APT-Candidate:** (optional, defaults to `no`). Allowed values:
   `yes`, `no`. When set to `yes`, the corresponding package is the APT
   candidate for installation among all available packages with the same
-  name.
+  name and architecture.
 
 - **APT-Automatic:** (optional, defaults to `no`). Allowed values:
   `yes`, `no`. When set to `yes`, the corresponding package is marked by
@@ -201,6 +218,22 @@ field. The following fields are supported in package stanzas:
   should be removed by the solver only when the Autoremove action is
   requested (see Request section).
 
+- **APT-Release:** (optional) The releases the package belongs to, according to
+  APT. The format of this field is multiline with one value per line and the
+  first line (the one containing the field name) empty. Each subsequent line
+  corresponds to one of the releases the package belongs to and looks like
+  this: `o=Debian,a=unstable,n=sid,l=Debian,c=main`. That is, each release line
+  is a comma-separated list of "key=value" pairs, each of which denotes a
+  Release file entry (Origin, Label, Codename, etc.) in the format of
+  APT_PREFERENCES(5).
+
+- **Source:** (optional) The name of the source package the binary
+  package this record is for was built from.
+  This field does NOT include the version of the source package unlike
+  the Source field in the dpkg database. The version is optionally
+  available in the **Source-Version:** field.
+
+
 ### Answer
 
 An answer from the external solver to APT is either a *solution* or an
@@ -209,11 +242,11 @@ An answer from the external solver to APT is either a *solution* or an
 The following invariant on **exit codes** must hold true. When the
 external solver is *able to find a solution*, it will write the solution
 to standard output and then exit with an exit code of 0. When the
-external solver is *unable to find a solution* (and s aware of that), it
-will write an error to standard output and then exit with an exit code
-of 0. An exit code other than 0 will be interpreted as a solver crash
-with no meaningful error about dependency resolution to convey to the
-user.
+external solver is *unable to find a solution* (and is aware of that),
+it will write an error to standard output and then exit with an exit
+code of 0. An exit code other than 0 will be interpreted as a solver
+crash with no meaningful error about dependency resolution to convey to
+the user.
 
 
 #### Solution