Implement luacov.runner.with_luacov

Useful when using luacov with coroutines created via C API.
It's possible to get and set the luacov debug hook manually, but
the debug.sethook call itself won't be covered.
When with_luacov() is used, the call happens inside luacov.

runner.with_luacov can be called before runner.init, triggering
a hook call before luacov state is ready. Add a guard for that.

Ref #38

1 files changed, 19 insertions, 0 deletions

diff --git a/src/luacov/runner.lua b/src/luacov/runner.lua
index 7e7e7b4..70668fc 100644
--- a/src/luacov/runner.lua
+++ b/src/luacov/runner.lua
@@ -24,6 +24,7 @@ local data
 local statsfile
 local tick
 local paused = true
+local initialized = false
 local ctr = 0
 
 local filelist = {}
@@ -89,6 +90,10 @@ end
 -- they may be absent if it's called from a sandboxed environment
 -- or because of carelessly implemented monkey-patching.
 local function on_line(_, line_nr)
+   if not initialized then
+      return
+   end
+
    if tick then
       ctr = ctr + 1
       if ctr == runner.configuration.savestepsize then
@@ -397,6 +402,18 @@ local function has_hook_per_thread()
 end
 
 --------------------------------------------------
+-- Wraps a function to be used in a coroutine created via C API.
+-- @param f function
+-- @return function that enables coverage gathering for current thread
+-- and calls original function.
+function runner.with_luacov(f)
+   return function(...)
+      debug.sethook(on_line, "l")
+      return f(...)
+   end
+end
+
+--------------------------------------------------
 -- Initializes LuaCov runner to start collecting data.
 -- @param[opt] configuration if string, filename of config file (used to call `load_config`).
 -- If table then config table (see file `luacov.default.lua` for an example)
@@ -444,6 +461,8 @@ function runner.init(configuration)
          end
       end
    end
+
+   initialized = true
 end
 
 --------------------------------------------------