warn if an expected file can't be acquired

If we couldn't find an entry for a Sources file we would generate an
error while for a Packages file we would silently skip it due to
assuming it is missing because it is empty. We can do better by checking
if the repository declares that it supports a component we want to get
the file from and if not say so and hint at the user making a typo.

An example were this helps is mozilla.debian.net which dropped the
firefox-aurora component (as upstream did) meaning no upgrades until the
user notices manually that the repository doesn't provide packages
anymore. With this commit warnings are raised hopefully causing the user
to investigate what is wrong (sooner).

2 files changed, 19 insertions, 0 deletions

diff --git a/apt-pkg/deb/debmetaindex.cc b/apt-pkg/deb/debmetaindex.cc
index cba00aa8e..8c82414cb 100644
--- a/apt-pkg/deb/debmetaindex.cc
+++ b/apt-pkg/deb/debmetaindex.cc
@@ -51,6 +51,7 @@ class APT_HIDDEN debReleaseIndexPrivate					/*{{{*/
 
    std::vector<std::string> Architectures;
    std::vector<std::string> NoSupportForAll;
+   std::vector<std::string> SupportedComponents;
    std::map<std::string, std::string> const ReleaseOptions;
 
    debReleaseIndexPrivate(std::map<std::string, std::string> const &Options) : CheckValidUntil(metaIndex::TRI_UNSET), ValidUntilMin(0), ValidUntilMax(0), ReleaseOptions(Options) {}
@@ -404,6 +405,16 @@ bool debReleaseIndex::Load(std::string const &Filename, std::string * const Erro
       if (targets.empty() == false)
 	 d->NoSupportForAll = VectorizeString(targets, ' ');
    }
+   for (auto const &comp: VectorizeString(Section.FindS("Components"), ' '))
+   {
+      if (comp.empty())
+	 continue;
+      auto const pos = comp.find_last_of('/');
+      if (pos == std::string::npos)
+	 d->SupportedComponents.push_back(std::move(comp));
+      else // e.g. security.debian.org uses this style
+	 d->SupportedComponents.push_back(comp.substr(pos + 1));
+   }
 
    bool FoundHashSum = false;
    bool FoundStrongHashSum = false;
@@ -733,6 +744,13 @@ bool debReleaseIndex::IsArchitectureAllSupportedFor(IndexTarget const &target) c
    return std::find(d->NoSupportForAll.begin(), d->NoSupportForAll.end(), target.Option(IndexTarget::CREATED_BY)) == d->NoSupportForAll.end();
 }
 									/*}}}*/
+bool debReleaseIndex::HasSupportForComponent(std::string const &component) const/*{{{*/
+{
+   if (d->SupportedComponents.empty())
+      return true;
+   return std::find(d->SupportedComponents.begin(), d->SupportedComponents.end(), component) != d->SupportedComponents.end();
+}
+									/*}}}*/
 std::vector <pkgIndexFile *> *debReleaseIndex::GetIndexFiles()		/*{{{*/
 {
    if (Indexes != NULL)
diff --git a/apt-pkg/deb/debmetaindex.h b/apt-pkg/deb/debmetaindex.h
index f903617f7..450ca94c9 100644
--- a/apt-pkg/deb/debmetaindex.h
+++ b/apt-pkg/deb/debmetaindex.h
@@ -61,6 +61,7 @@ class APT_HIDDEN debReleaseIndex : public metaIndex
    virtual bool IsTrusted() const APT_OVERRIDE;
    bool IsArchitectureSupported(std::string const &arch) const;
    bool IsArchitectureAllSupportedFor(IndexTarget const &target) const;
+   bool HasSupportForComponent(std::string const &component) const;
 
    void AddComponent(std::string const &sourcesEntry,
 	 bool const isSrc, std::string const &Name,