feat: support for multi-stage builds

lib/index.js

@@ -50,8 +50,10 @@ module.exports.run = function(configPath, content) {
   });
 
   var state = {
-    instructionsProcessed: 0,
-    cmdFound: false,
+    stages: [{
+      instructionsProcessed: 0,
+      cmdFound: false // this doesn't seem to be used anywhere
+    }],
     items: [],
     rules: loadRules(configPath)
   }
@@ -62,11 +64,17 @@ module.exports.run = function(configPath, content) {
 
     // We care about only having 1 cmd instruction
     if (result.command === 'cmd') {
-      state.cmdFound = true;
+      state.stages[state.stages.length - 1].cmdFound = true;
+    } else if (result.command === 'from' && state.stages[state.stages.length - 1].instructionsProcessed !== 0) {
+      // Each FROM command constitutes a new stage in a multistage build
+      state.stages.push({
+        instructionsProcessed: 0,
+        cmdFound: false
+      });
     }
 
     // And we also care about knowing if this is the first command or not
-    state.instructionsProcessed = state.instructionsProcessed + 1;
+    state.stages[state.stages.length - 1].instructionsProcessed++;
   };
 
   return state.items;
@@ -116,7 +124,7 @@ function runLine(state, instructions, idx) {
 
   // check that the first command is a FROM, this might get reported twice, if the FROM command does exist,
   // but is not the time (non blank, non commented) line
-  if ((state.instructionsProcessed === 0 && cmd !== 'from') || (state.instructionsProcessed !== 0 && cmd === 'from')) {
+  if (state.stages[state.stages.length - 1].instructionsProcessed === 0 && cmd !== 'from') {
     items.push(messages.build(state.rules, 'from_first', line));
   }
 

test/examples/Dockerfile.multistage

@@ -0,0 +1,11 @@
+FROM golang:1.7.3
+WORKDIR /go/src/github.com/alexellis/href-counter/
+RUN go get -d -v golang.org/x/net/html
+COPY app.go .
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .
+
+FROM alpine:3.6
+RUN apk --no-cache add ca-certificates
+WORKDIR /root/
+COPY --from=0 /go/src/github.com/alexellis/href-counter/app .
+CMD ["./app"]

test/examples/Dockerfile.multistagenamed

@@ -0,0 +1,11 @@
+FROM golang:1.7.3 as builder
+WORKDIR /go/src/github.com/alexellis/href-counter/
+RUN go get -d -v golang.org/x/net/html
+COPY app.go .
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .
+
+FROM alpine:3.6
+RUN apk --no-cache add ca-certificates
+WORKDIR /root/
+COPY --from=builder /go/src/github.com/alexellis/href-counter/app .
+CMD ["./app"]

test/index.js

@@ -64,6 +64,16 @@ describe("index", function(){
     });
   });
 
+  describe("#multistage", function(){
+    it("validates the multistage Dockerfile has no issues", function(){
+      expect(dockerfilelint.run('./test/examples', fs.readFileSync('./test/examples/Dockerfile.multistage', 'UTF-8'))).to.be.empty;
+    });
+
+    it("validates the multistagenamed Dockerfile has no issues", function(){
+      expect(dockerfilelint.run('./test/examples', fs.readFileSync('./test/examples/Dockerfile.multistagenamed', 'UTF-8'))).to.be.empty;
+    });
+  });
+
   describe("#shell", function() {
     it("validates the shell command is accepted when entered correctly", function() {
       expect(dockerfilelint.run('./test/examples', fs.readFileSync('./test/examples/Dockerfile.shell.pass', 'UTF-8'))).to.be.empty;
@@ -91,15 +101,9 @@ describe("index", function(){
           { title: 'First Command Must Be FROM',
             rule: 'from_first',
             line: 4 },
-          { title: 'First Command Must Be FROM',
-            rule: 'from_first',
-            line: 5 },
           { title: 'Base Image Missing Tag',
             rule: 'missing_tag',
             line: 5 },
-          { title: 'First Command Must Be FROM',
-            rule: 'from_first',
-            line: 6 },
           { title: 'Base Image Latest Tag',
             rule: 'latest_tag',
             line: 6 },