ci(gofmt): check go formatting with each PR

.circleci/config.yml

@@ -43,6 +43,7 @@ jobs:
             - platform-gocache-                              # Matches a new branch.
       - run: make test-go # This uses the test cache so it may succeed or fail quickly.
       - run: make vet
+      - run: make checkfmt
       - run: make test-go-race # This doesn't use the test cache, and will not complete quickly.
       # TODO add these checks to the Makefile
       # - run: go get -v -t -d ./...

Makefile

@@ -105,7 +105,10 @@ chronograf/ui/build:
 #
 
 fmt: $(SOURCES_NO_VENDOR)
-	goimports -w $^
+	gofmt -w -s $^
+
+checkfmt: $(SOURCES_NO_VENDOR)
+	./etc/checkfmt.sh
 
 chronograf/dist/dist_gen.go: chronograf/ui/build $(UISOURCES)
 	 $(GO_GENERATE) ./chronograf/dist/...

etc/checkfmt.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+HAS_FMT_ERR=0
+# For every Go file in the project, excluding vendor...
+for file in $(go list -f '{{$dir := .Dir}}{{range .GoFiles}}{{printf "%s/%s\n" $dir .}}{{end}}' ./...); do
+  # ... if file does not contain standard generated code comment (https://golang.org/s/generatedcode)...
+  if ! grep -Exq '^// Code generated .* DO NOT EDIT\.$' $file; then
+    FMT_OUT="$(gofmt -l -d -e $file)" # gofmt exits 0 regardless of whether it's formatted.
+    # ... and if gofmt had any output...
+    if [[ -n "$FMT_OUT" ]]; then
+      if [ "$HAS_FMT_ERR" -eq "0" ]; then
+        # Only print this once.
+        HAS_FMT_ERR=1
+        echo 'Commit includes files that are not gofmt-ed' && \
+        echo 'run "make fmt"' && \
+        echo ''
+      fi
+      echo "$FMT_OUT" # Print output and continue, so developers don't fix one file at a t
+    fi
+   fi
+done
+
+## print at the end too... sometimes it is nice to see what to do at the end.
+if [ "$HAS_FMT_ERR" -eq "1" ]; then
+    echo 'Commit includes files that are not gofmt-ed' && \
+    echo 'run "make fmt"' && \
+    echo ''
+fi
+exit "$HAS_FMT_ERR"