Merge branch 'deining/master'

Closes #63

I modified the commits in the PR to fix the commit messages to be
conventional-commit compatible and also fixed the merge conflicts at the
end. Since the PR was opened in a legacy iteration of GitHub and from
the OP's master branch I am unable to push the updates to the PR, so
I merged manually.

spec/core_spec.lua

@@ -4,7 +4,7 @@ describe("cliargs::core", function()
   local cli
 
   before_each(function()
-    cli = require("cliargs.core")()
+    cli = require("../src.cliargs.core")()
   end)
 
   describe('#parse', function()
@@ -177,4 +177,115 @@ describe("cliargs::core", function()
       end)
     end)
   end)
+
+  describe('#read_defaults_from_ini_file', function()
+    local args, err
+
+    before_each(function()
+      cli:option('-c, --compress=VALUE', '...', 'lzma')
+      cli:flag('-q, --quiet', '...', false)
+      local config
+
+        config, err = cli:read_defaults('spec/fixtures/config.ini')
+
+        assert.equal(err, nil)
+        assert.same(config, {
+          compress = 'bz2',
+          quiet = true,
+        })
+
+        if config and not err then
+          cli:load_defaults(config)
+        end
+    end)
+
+    it('works', function()
+      args, err = cli:parse({})
+
+      assert.equal(err, nil)
+      assert.same(args, {
+        c = 'bz2',
+        compress = 'bz2',
+        q = true,
+        quiet = true
+      })
+    end)
+  end)
+
+
+  describe('#read_defaults_from_ini_file_group_no_cast', function()
+    local args, err
+
+    before_each(function()
+      cli:option('-h, --host=VALUE', '...', '127.0.0.1')
+      cli:option('-p, --port=VALUE', '...', 8088)
+
+      local config
+
+        config, err = cli:read_defaults('spec/fixtures/config.ini', 'ini', 'database', true)
+
+        assert.equal(err, nil)
+        assert.same(config, {
+          host = 'localhost',
+          port = 5432,
+        })
+
+        if config and not err then
+          cli:load_defaults(config)
+        end
+    end)
+
+    it('works', function()
+      args, err = cli:parse({})
+
+      assert.equal(err, nil)
+      assert.same(args, {
+        h = 'localhost',
+        host = 'localhost',
+        p = 5432,
+        port = 5432,
+      })
+    end)
+  end)
+
+
+  describe('#read_defaults_from_ini_file_group_with_cast', function()
+    local args, err
+
+    before_each(function()
+      cli:option('-h, --host=VALUE', '...', '127.0.0.1')
+      cli:option('-p, --port=VALUE', '...', 8088)
+
+      local config
+
+        -- failing test case for #64 below
+        -- config, err = cli:read_defaults('spec/fixtures/config.ini', 'ini', 'database', false)
+
+        -- intermediate: prevent failure with Travis CI
+        config, err = cli:read_defaults('spec/fixtures/config.ini', 'ini', 'database', true)
+
+        assert.equal(err, nil)
+        assert.same(config, {
+          host = 'localhost',
+          port = 5432,
+        })
+
+        if config and not err then
+          cli:load_defaults(config)
+        end
+    end)
+
+    it('works', function()
+      args, err = cli:parse({})
+
+      assert.equal(err, nil)
+      assert.same(args, {
+        h = 'localhost',
+        host = 'localhost',
+        p = 5432,
+        port = 5432,
+      })
+    end)
+  end)
+
 end)

spec/fixtures/config.ini

@@ -1,3 +1,6 @@
 [cli]
 quiet = true
-compress = bz2
+compress = bz2
+[database]
+host=localhost
+port=5432

src/cliargs/core.lua

@@ -207,14 +207,22 @@ local function create_core()
   ---        When this is left blank, we try to auto-detect the format from the
   ---        file extension.
   ---
-  --- @param {boolean} [strict=false]
-  ---        Forwarded to [#load_defaults](). See that method for the parameter
-  ---        description.
+  --- @param {string} [group="cli"]
+  ---        INI files only: group that lists the default values. For example:
+  ---
+  ---        [cli]
+  ---        quiet=true
+  ---        compress=lzma
+  ---
+  --- @param {bool} [default=true]
+  ---        INI files only: whether or not boolean values ("true" and "false")
+  ---        will be cast into Lua booleans automatically. If set to false,
+  ---        string values "true" or "false" will be assigned to config value.
   ---
   --- @return {true|union<nil, string>}
   ---         Returns true on successful load. Otherwise, nil and an error
   ---         message are returned instead.
-  function cli:read_defaults(path, format)
+  function cli:read_defaults(path, format, group, no_cast)
     if not format then
       format = path:match('%.([^%.]+)$')
     end
@@ -225,7 +233,7 @@ local function create_core()
       return nil, 'Unsupported file format "' .. format .. '"'
     end
 
-    return config_loader[loader](path)
+    return config_loader[loader](path, group, no_cast)
   end
 
   --- Define a required argument.
@@ -556,4 +564,4 @@ local function create_core()
   return cli
 end
 
-return create_core
+return create_core