support non-cloud providers and backends

* decouple backend detection from plugins
* expander backend detection that doesn't evaluate ERB
* adjust default max retries for backend re-init to 1

lib/terraspace/compiler/backend.rb

@@ -16,6 +16,7 @@ def create
       klass = backend_interface(backend_name)
       return unless klass # in case auto-creation is not supported for specific backend
 
+      # IE: TerraspacePluginAws::Interfaces::Backend.new
       interface = klass.new(backend_info)
       interface.call
     end

lib/terraspace/compiler/expander.rb

@@ -1,17 +1,21 @@
 module Terraspace::Compiler
   class Expander
+    extend Memoist
     delegate :expand, :expansion, to: :expander
 
-    attr_reader :expander
     def initialize(mod, name)
       @mod, @name = mod, name
-      @expander = expander_class.new(@mod)
     end
 
+    def expander
+      expander_class.new(@mod)
+    end
+    memoize :expander
+
     def expander_class
       # IE: TerraspacePluginAws::Interfaces::Expander
       klass_name = Terraspace::Plugin.klass("Expander", backend: @name)
-      klass_name.constantize if klass_name
+      klass_name ? klass_name.constantize : Terraspace::Plugin::Expander::Generic
     rescue NameError
       Terraspace::Plugin::Expander::Generic
     end
@@ -20,27 +24,15 @@ class << self
       extend Memoist
 
       def autodetect(mod, opts={})
-        backend = opts[:backend]
-        unless backend
-          plugin = find_plugin
-          backend = plugin[:backend]
-        end
+        backend = opts[:backend] || find_backend(mod)
         new(mod, backend)
       end
       memoize :autodetect
 
-      def find_plugin
-        plugins = Terraspace::Plugin.meta
-        if plugins.size == 1
-          plugins.first[1]
-        else
-          precedence = %w[aws azurerm google]
-          plugin = precedence.find do |provider|
-            plugins[provider]
-          end
-          plugins[plugin]
-        end
+      def find_backend(mod)
+        Backend.new(mod).detect
       end
+      memoize :find_backend
     end
   end
 end

lib/terraspace/compiler/expander/backend.rb

@@ -0,0 +1,43 @@
+# Simpler than Terraspace::Compiler::Backend::Parser because
+# Terraspace::Compiler::Expander autodetect backend super early on.
+# It's so early that don't want helper methods like <%= expansion(...) %> to be called.
+# Calling the expansion helper itself results in Terraspace autodetecting a concrete
+# Terraspace Plugin Expander, which creates an infinite loop.
+# This simple detection class avoids calling ERB and avoids the infinite loop.
+class Terraspace::Compiler::Expander
+  class Backend
+    extend Memoist
+
+    def initialize(mod)
+      @mod = mod
+    end
+
+    COMMENT = /^\s+#/
+    # Works for both backend.rb DSL and backend.tf ERB
+    def detect
+      lines = IO.readlines(src_path)
+      backend_line = lines.find { |l| l.include?("backend") && l !~ COMMENT }
+      md = backend_line.match(/['"](.*)['"]/)
+      md[1] if md
+    end
+
+  private
+    # Use original unrendered source as wont know the
+    # @mod.cache_dir = ":CACHE_ROOT/:REGION/:ENV/:BUILD_DIR"
+    # Until the concrete Terraspace Plugin Expander has been autodetected.
+    # Follow same precedence rules as rest of Terraspace.
+    def src_path
+      exprs = [
+        "app/stacks/#{@mod.build_dir}/backend.*",
+        "app/modules/#{@mod.build_dir}/backend.*",
+        "vendor/stacks/#{@mod.build_dir}/backend.*",
+        "vendor/modules/#{@mod.build_dir}/backend.*",
+        "config/terraform/backend.*",
+      ]
+      path = nil
+      exprs.find { |expr| path = Dir.glob(expr).first }
+      path
+    end
+    memoize :src_path
+  end
+end

lib/terraspace/plugin/expander/interface.rb

@@ -70,7 +70,10 @@ def expand_string?(string)
     #
     def strip(string)
       string.sub(/^-+/,'').sub(/-+$/,'') # remove leading and trailing -
-            .sub(%r{/+$},'') # only remove trailing / or else /home/ec2-user => home/ec2-user
+            .sub(%r{/+$},'')  # only remove trailing / or else /home/ec2-user => home/ec2-user
+            .sub(/:\/\//, 'TMP_KEEP_HTTP') # so we can keep ://. IE: https:// or http://
+            .gsub(%r{/+},'/') # remove double slashes are more. IE: // -> / Useful of region is '' in generic expander
+            .sub('TMP_KEEP_HTTP', '://')   # restore :// IE: https:// or http://
     end
 
     def var_value(name)
@@ -102,5 +105,13 @@ def instance
     def cache_root
       Terraspace.cache_root
     end
+
+    # So default config works:
+    #    config.cache_dir = ":CACHE_ROOT/:REGION/:ENV/:BUILD_DIR"
+    # For when folks configure it with the http backend for non-cloud providers
+    # The double slash // will be replace with a single slash in expander/interface.rb
+    def region
+      ''
+    end
   end
 end

lib/terraspace/terraform/runner/retryer.rb

@@ -9,7 +9,7 @@ def initialize(mod, options, command_name, exception)
     end
 
     def retry?
-      max_retries = ENV['TS_MAX_RETRIES'] ? ENV['TS_MAX_RETRIES'].to_i : 3
+      max_retries = ENV['TS_MAX_RETRIES'] ? ENV['TS_MAX_RETRIES'].to_i : 1
       if @retries <= max_retries && !@stop_retrying
         true # will retry
       else