GLAMOUR_STYLE environment variable support (#69)

README.md

@@ -55,6 +55,11 @@ fmt.Print(out)
 You can find all available default styles in our [gallery](https://github.com/charmbracelet/glamour/tree/master/styles/gallery).
 Want to create your own style? [Learn how!](https://github.com/charmbracelet/glamour/tree/master/styles)
 
+There are a few options for using a custom style:
+1. Call `glamour.Render(inputText, "desiredStyle")`
+1. Set the `GLAMOUR_STYLE` environment variable to your desired default style or a file location for a style and call `glamour.RenderWithEnvironmentConfig(inputText)`
+1. Set the `GLAMOUR_STYLE` environment variable and pass `glamour.WithEnvironmentConfig()` to your custom renderer
+
 
 ## Glamourous Projects
 

glamour.go

@@ -36,6 +36,13 @@ func Render(in string, stylePath string) (string, error) {
 	return string(b), err
 }
 
+// RenderWithEnvironmentConfig initializes a new TermRenderer and renders a
+// markdown with a specific style defined by the GLAMOUR_STYLE environment variable.
+func RenderWithEnvironmentConfig(in string) (string, error) {
+	b, err := RenderBytes([]byte(in), getEnvironmentStyle())
+	return string(b), err
+}
+
 // RenderBytes initializes a new TermRenderer and renders a markdown with a
 // specific style.
 func RenderBytes(in []byte, stylePath string) ([]byte, error) {
@@ -117,6 +124,12 @@ func WithAutoStyle() TermRendererOption {
 	return WithStandardStyle("auto")
 }
 
+// WithEnvironmentConfig sets a TermRenderer's styles based on the
+// GLAMOUR_STYLE environment variable.
+func WithEnvironmentConfig() TermRendererOption {
+	return WithStylePath(getEnvironmentStyle())
+}
+
 // WithStylePath sets a TermRenderer's style from stylePath. stylePath is first
 // interpreted as a filename. If no such file exists, it is re-interpreted as a
 // standard style.
@@ -207,6 +220,15 @@ func (tr *TermRenderer) RenderBytes(in []byte) ([]byte, error) {
 	return buf.Bytes(), err
 }
 
+func getEnvironmentStyle() string {
+	glamourStyle := os.Getenv("GLAMOUR_STYLE")
+	if len(glamourStyle) == 0 {
+		glamourStyle = "auto"
+	}
+
+	return glamourStyle
+}
+
 func getDefaultStyle(style string) (*ansi.StyleConfig, error) {
 	if style == "auto" {
 		if termenv.HasDarkBackground() {

glamour_test.go

@@ -104,6 +104,13 @@ func TestStyles(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
+	_, err = NewTermRenderer(
+		WithEnvironmentConfig(),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestRenderHelpers(t *testing.T) {

go.sum

@@ -12,6 +12,7 @@ github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964/go.mod h1:Xd9
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dlclark/regexp2 v1.2.0 h1:8sAhBGEM0dRWogWqWyQeIJnxjWO6oIjl8FKqREDsGfk=
 github.com/dlclark/regexp2 v1.2.0/go.mod h1:2pZnwuY/m+8K6iRw6wQdMtk+rH5tNGR1i55kozfMjCc=
 github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f h1:5CjVwnuUcp5adK4gmY6i72gpVFVnZDP2h5TmPScB6u4=
 github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f/go.mod h1:nOFQdrUlIlx6M6ODdSpBj1NVA+VgLC6kmw60mkw34H4=