envfile support

README.md

@@ -1,12 +1,11 @@
 # Dockerfile+
 
-This project provides Dockerfile syntax extensions that have been rejected by the moby project or haven't been addressed in a long time.
-
-Currently, the project adds an `INCLUDE+` Dockerfile directive that allows you to import the content of another file into your Dockerfile. There are plans to add more features in the near future.
+This project provides useful Dockerfile syntax extensions that have been rejected by the moby project or haven't been addressed in a long time.
 
 - [Getting started](#getting-started)
 - [Features](#features)
   - [INCLUDE+](#include)
+  - [ENVFILE+](#envfile)
 - [Roadmap](#roadmap)
 - [Feedback](#feedback)
 
@@ -27,9 +26,9 @@ That's it!
 
 ## Features
 
-### INCLUDE+
+Note: All Dockerfile+ commands will end up with a `+` sign to avoid any potential future collisions with Dockerfile commands.
 
-Right now there is just one extra instruction: `INCLUDE+`. All Dockerfile+ commands will end up with a `+` sign to avoid any potential future collisions with Dockerfile commands.
+### INCLUDE+
 
 `INCLUDE+` will import the verbatim contents of another file into your Dockerfile. Here's an example Dockerfile which uses the `INCLUDE+` instruction:
 
@@ -54,11 +53,45 @@ RUN echo "Hello World"
 ENTRYPOINT [ "mybin" ]
 ```
 
+### ENVFILE+
+
+docker-compose has had support for envfiles for a while now, but Dockerfile hasn't. The `ENVFILE+` instruction brings that support to Dockerfile! If you `ENVFILE+` a .env file, each line will be treated as an `ENV` definition. Here's an example:
+
+```Dockerfile
+# syntax = edrevo/dockerfile-plus
+
+FROM alpine
+
+ENVFILE+ prod.env
+
+ENTRYPOINT [ "mybin" ]
+```
+
+If prod.env has the following:
+
+```env
+FOO=Hello
+BAR=World
+```
+
+The resulting Docker image would be equivalent to the one generated by this standard Dockerfile:
+
+```Dockerfile
+# syntax = edrevo/dockerfile-plus
+
+FROM alpine
+
+ENV FOO=Hello
+
+ENV BAR=World
+
+ENTRYPOINT [ "mybin" ]
+```
+
 ## Roadmap
 
 The next features in line would be:
 
-- `ENVFILE+` command, which would read a .env file and import all of those environment variable definitions into the Dockerfile
 - `RUN+ --no-cache`, which would disable the cache only for a specific RUN step (useful for non-idempotent commands, for example those that clone git repos)
 - `TAG` command
 - improvements to .dockerignore, like recursive dockerignore files

dockerfile-plus/examples/envfile/Dockerfile

@@ -0,0 +1,9 @@
+# syntax = edrevo/dockerfile-plus:0.2
+
+FROM alpine
+
+ENVFILE+ dev.env
+
+WORKDIR /
+
+RUN echo "Hello World"

dockerfile-plus/examples/envfile/dev.env

@@ -0,0 +1,3 @@
+MEAN_STORE_PORT = 4200
+MEAN_STORE_SECRET = "dummy_secret"
+MEAN_STORE_DATABASE = "dummy_connection"

dockerfile-plus/src/main.rs

@@ -104,6 +104,7 @@ struct DockerfileOptions {
 }
 
 const INCLUDE_COMMAND: &str = "INCLUDE+";
+const ENVFILE_COMMAND: &str = "ENVFILE+";
 
 async fn dockerfile_trap(
     mut client: LlbBridgeClient<Channel>,
@@ -114,11 +115,19 @@ async fn dockerfile_trap(
     let context_source = Source::local("context");
     let context_layer = solve(&mut client, Terminal::with(context_source.output())).await?;
     for line in dockerfile_contents.lines() {
-        if let Some(file_path) = line.trim().strip_prefix(INCLUDE_COMMAND) {
+        let trimmed_line = line.trim();
+        if let Some(file_path) = trimmed_line.strip_prefix(INCLUDE_COMMAND) {
             let bytes = read_file(&mut client, &context_layer, file_path.trim_start().to_string(), None)
                 .await
                 .with_context(|| format!("Could not read file \"{}\". Remember that the file path is relative to the build context, not the Dockerfile path.", file_path))?;
             result.push(std::str::from_utf8(&bytes)?.to_string());
+        } else if let Some(file_path) = trimmed_line.strip_prefix(ENVFILE_COMMAND) {
+            let bytes = read_file(&mut client, &context_layer, file_path.trim_start().to_string(), None)
+                .await
+                .with_context(|| format!("Could not read file \"{}\". Remember that the file path is relative to the build context, not the Dockerfile path.", file_path))?;
+            for env_line in std::str::from_utf8(&bytes)?.lines() {
+                result.push(format!("ENV {}", env_line));
+            }
         } else {
             result.push(line.to_string());
         }