builtin: if "libraries" is used but "external_dependencies" is not given, autogenerate it

The approach is slightly ugly since it adds builtin-specific
knowledge to `luarocks.deps`, but I don't think any other
build backends will support this behavior any time soon.

3 files changed, 63 insertions, 0 deletions

diff --git a/spec/build_spec.lua b/spec/build_spec.lua
index af2dfe38..ae559654 100644
--- a/spec/build_spec.lua
+++ b/spec/build_spec.lua
@@ -311,6 +311,33 @@ describe("LuaRocks build tests #integration", function()
          assert.truthy(run.luarocks_bool("build " .. rockspec))
          assert.match("bla.lua", run.luarocks("show autodetect"))
       end)
+
+      it("'builtin' synthesizes external_dependencies if not given but a library is given in build", function()
+         local rockspec = "autodetect-1.0-1.rockspec"
+         test_env.write_file(rockspec, [[
+            rockspec_format = "3.0"
+            package = "autodetect"
+            version = "1.0-1"
+            source = {
+               url = "file://]] .. testing_paths.fixtures_dir .. [[/c_module.c"
+            }
+            description = {
+               summary = "An example rockspec",
+            }
+            dependencies = {
+               "lua >= 5.1"
+            }
+            build = {
+               modules = {
+                  c_module = {
+                     sources = "c_module.c",
+                     libraries = "inexistent_library",
+                  }
+               }
+            }
+         ]], finally)
+         assert.match("INEXISTENT_LIBRARY_DIR", run.luarocks("build " .. rockspec))
+      end)
    end)
 
    describe("#mock external dependencies", function()
diff --git a/src/luarocks/build/builtin.lua b/src/luarocks/build/builtin.lua
index 4ff59f8b..f414c166 100644
--- a/src/luarocks/build/builtin.lua
+++ b/src/luarocks/build/builtin.lua
@@ -10,6 +10,38 @@ local util = require("luarocks.util")
 local cfg = require("luarocks.core.cfg")
 local dir = require("luarocks.dir")
 
+function builtin.autodetect_external_dependencies(build)
+   if not build or not build.modules then
+      return nil
+   end
+   local extdeps = {}
+   local any = false
+   for _, data in pairs(build.modules) do
+      if type(data) == "table" and data.libraries then
+         local libraries = data.libraries
+         if type(libraries) == "string" then
+            libraries = { libraries }
+         end
+         local incdirs = {}
+         local libdirs = {}
+         for _, lib in ipairs(libraries) do
+            local upper = lib:upper()
+            any = true
+            extdeps[upper] = { library = lib }
+            table.insert(incdirs, "$(" .. upper .. "_INCDIR)")
+            table.insert(libdirs, "$(" .. upper .. "_LIBDIR)")
+         end
+         if not data.incdirs then
+            data.incdirs = incdirs
+         end
+         if not data.libdirs then
+            data.libdirs = libdirs
+         end
+      end
+   end
+   return any and extdeps or nil
+end
+
 local function autoextract_libs(external_dependencies, variables)
    if not external_dependencies then
       return nil, nil, nil
diff --git a/src/luarocks/deps.lua b/src/luarocks/deps.lua
index 3ec1aa93..bcd6ccf5 100644
--- a/src/luarocks/deps.lua
+++ b/src/luarocks/deps.lua
@@ -9,6 +9,7 @@ local dir = require("luarocks.dir")
 local util = require("luarocks.util")
 local vers = require("luarocks.core.vers")
 local queries = require("luarocks.queries")
+local builtin = require("luarocks.build.builtin")
 
 --- Attempt to match a dependency to an installed rock.
 -- @param dep table: A dependency parsed in table format.
@@ -277,6 +278,9 @@ function deps.check_external_deps(rockspec, mode)
       patterns = cfg.runtime_external_deps_patterns
       subdirs = cfg.runtime_external_deps_subdirs
    end
+   if not rockspec.external_dependencies then
+      rockspec.external_dependencies = builtin.autodetect_external_dependencies(rockspec.build)
+   end
    if rockspec.external_dependencies then
       for name, ext_files in util.sortedpairs(rockspec.external_dependencies) do
          local ok = true