fix(app) require_here follow symlink'd main module (#423)

CHANGELOG.md

@@ -9,6 +9,8 @@ see [CONTRIBUTING.md](CONTRIBUTING.md#release-instructions-for-a-new-version) fo
 ## 1.13.0 (unreleased)
  - fix: `xml.parse` returned nonsense when given a file name
    [#431](https://github.com/lunarmodules/Penlight/pull/431)
+ - feat: `app.require_here` now follows symlink'd main modules to their directory
+   [#423](https://github.com/lunarmodules/Penlight/pull/423)
  - fix: `compat.warn` raised write guard warning in OpenResty
    [#414](https://github.com/lunarmodules/Penlight/pull/414)
  - feat: `utils.enum` now accepts hash tables, to enable better error handling

lua/pl/app.lua

@@ -29,12 +29,24 @@ end
 --
 -- Note: the path is prefixed, so it is searched first when requiring modules.
 -- @string base optional base directory (absolute, or relative path).
+-- @bool nofollow always use the invocation's directory, even if the invoked file is a symlink
 -- @treturn string the current script's path with a trailing slash
-function app.require_here (base)
-    local p = path.dirname(app.script_name())
+function app.require_here (base, nofollow)
+    local p = app.script_name()
     if not path.isabs(p) then
         p = path.join(path.currentdir(),p)
     end
+    if not nofollow then
+      local t = path.link_attrib(p)
+      if t and t.mode == 'link' then
+        t = t.target
+        if not path.isabs(t) then
+          t = path.join(path.dirname(p), t)
+        end
+        p = t
+      end
+    end
+    p = path.normpath(path.dirname(p))
     if p:sub(-1,-1) ~= path.sep then
         p = p..path.sep
     end

tests/test-app.lua

@@ -2,6 +2,7 @@ local app = require "pl.app"
 local utils = require "pl.utils"
 local path = require "pl.path"
 local asserteq = require 'pl.test'.asserteq
+local lfs = require("lfs")
 
 local quote = utils.quote_arg
 
@@ -117,6 +118,32 @@ do  -- app.require_here
     stdout = path.normcase(stdout)
     asserteq(stdout, path.normcase("/fixed/?.lua;/fixed/?/init.lua;\n"))
 
+    -- symlinked script, check that we look beside the target of the link
+    -- -- step 1: find ourselves
+    local self = app.script_name()
+    if not path.isabs(self) then self = path.join(cd,self) end
+    local tadir = path.normcase(path.join(path.dirname(self),"test-app"))
+    -- -- step 2: create a link to our helper script
+    local scrl = path.tmpname()
+    local linkdir = path.normcase(path.dirname(scrl))
+    os.remove(scrl)
+    assert(lfs.link(path.join(tadir,"require_here-link-target.lua"), scrl, true))
+    -- -- step 3: check that we look next to ourselves
+    local success, code, stdout, stderr = utils.executeex(cmd.." "..scrl)
+    stdout = path.normcase(stdout)
+    assert(stdout:find(path.normcase(path.join(tadir, "?.lua;")), 1, true))
+    assert(stdout:find(path.normcase(path.join(tadir, "?/init.lua;")), 1, true))
+    assert(not stdout:find(path.normcase(path.join(linkdir, "?.lua;")), 1, true))
+    assert(not stdout:find(path.normcase(path.join(linkdir, "?/init.lua;")), 1, true))
+    -- -- step 4: ... but not if we turn on nofollow
+    local success, code, stdout, stderr = utils.executeex(cmd.." "..scrl.." x")
+    stdout = path.normcase(stdout)
+    assert(not stdout:find(path.normcase(path.join(tadir, "?.lua;")), 1, true))
+    assert(not stdout:find(path.normcase(path.join(tadir, "?/init.lua;")), 1, true))
+    assert(stdout:find(path.normcase(path.join(linkdir, "?.lua;")), 1, true))
+    assert(stdout:find(path.normcase(path.join(linkdir, "?/init.lua;")), 1, true))
+    os.remove(scrl)
+
 end
 
 

tests/test-app/require_here-link-target.lua

@@ -0,0 +1,6 @@
+-- This file is used as a symbolic link target in test-app.lua, to verify the
+-- behaviors of pl.app.require_here()
+
+local p = package.path
+require("pl.app").require_here(nil, #arg > 0)
+print(package.path:sub(1, -#p-1))