Use String/Nil#presence in a few places throughout stdlib

src/compiler/crystal/compiler.cr

@@ -326,7 +326,7 @@ module Crystal
           object_name = %(%*)
         end
 
-        if (link_flags = @link_flags) && !link_flags.empty?
+        if link_flags = @link_flags.presence
           link_flags = "/link #{link_flags}"
         end
 

src/compiler/crystal/semantic/call_error.cr

@@ -459,7 +459,7 @@ class Crystal::Call
       str << '*' if a_def.splat_index == i
 
       if arg.external_name != arg.name
-        str << (arg.external_name.empty? ? '_' : arg.external_name)
+        str << (arg.external_name.presence || '_')
         str << ' '
       end
 

src/compiler/crystal/tools/doc/macro.cr

@@ -98,7 +98,7 @@ class Crystal::Doc::Macro
 
   def arg_to_s(arg : Arg, io : IO) : Nil
     if arg.external_name != arg.name
-      name = arg.external_name.empty? ? "_" : arg.external_name
+      name = arg.external_name.presence || "_"
       if Symbol.needs_quotes? name
         HTML.escape name.inspect, io
       else

src/compiler/crystal/tools/doc/method.cr

@@ -268,7 +268,7 @@ class Crystal::Doc::Method
 
   def arg_to_html(arg : Arg, io, links = true)
     if arg.external_name != arg.name
-      name = arg.external_name.empty? ? "_" : arg.external_name
+      name = arg.external_name.presence || "_"
       if Symbol.needs_quotes? name
         HTML.escape name.inspect, io
       else

src/compiler/crystal/tools/doc/type.cr

@@ -449,7 +449,7 @@ class Crystal::Doc::Type
       methods.find { |method| method.name == name && method.args.size == args_size }
     else
       methods = methods.select { |method| method.name == name }
-      (methods.find { |method| method.args.empty? }) || methods.first?
+      methods.find(&.args.empty?) || methods.first?
     end
   end
 

src/http/client.cr

@@ -828,8 +828,8 @@ class HTTP::Client
   {% end %}
 
   protected def self.validate_host(uri)
-    host = uri.host
-    return host if host && !host.empty?
+    host = uri.host.presence
+    return host if host
 
     raise ArgumentError.new %(Request URI must have host (URI is: #{uri}))
   end

src/http/request.cr

@@ -218,7 +218,7 @@ class HTTP::Request
 
   # Returns the request's path component.
   def path
-    (path = uri.path).empty? ? "/" : path
+    uri.path.presence || "/"
   end
 
   # Sets request's path component.

src/json/builder.cr

@@ -264,11 +264,7 @@ class JSON::Builder
 
   # Sets the indent *string*.
   def indent=(string : String)
-    if string.empty?
-      @indent = nil
-    else
-      @indent = string
-    end
+    @indent = string.presence
   end
 
   # Sets the indent *level* (number of spaces).

src/llvm.cr

@@ -89,7 +89,7 @@ module LLVM
 
     # Fix LLVM not replacing empty triple parts with "unknown"
     # This was fixed in LLVM 8
-    normalized = normalized.split('-').map { |c| c.empty? ? "unknown" : c }.join('-')
+    normalized = normalized.split('-').map { |c| c.presence || "unknown" }.join('-')
 
     normalized
   end

src/mime/multipart.cr

@@ -43,11 +43,7 @@ module MIME::Multipart
     type = MIME::MediaType.parse?(content_type)
 
     if type && type.type == "multipart"
-      boundary = type["boundary"]?
-
-      if boundary && !boundary.empty?
-        boundary
-      end
+      type["boundary"]?.presence
     end
   end
 

src/oauth/signature.cr

@@ -52,8 +52,7 @@ struct OAuth::Signature
         str << "%3A"
         str << port
       end
-      uri_path = request.path || "/"
-      uri_path = "/" if uri_path.empty?
+      uri_path = request.path.presence || "/"
       URI.encode_www_form(uri_path, str, space_to_plus: false)
       str << '&'
       str << params

src/socket/address.cr

@@ -128,7 +128,7 @@ class Socket
     # ```
     def self.parse(uri : URI) : IPAddress
       host = uri.host
-      raise Socket::Error.new("Invalid IP address: missing host") if !host || host.empty?
+      raise Socket::Error.new("Invalid IP address: missing host") unless host.presence
 
       port = uri.port || raise Socket::Error.new("Invalid IP address: missing port")
 
@@ -341,7 +341,7 @@ class Socket
         if port = uri.port
           io << ':' << port
         end
-        if (path = uri.path) && !path.empty?
+        if path = uri.path.presence
           io << path
         end
       end