From 4323b491304540e721d026dbb5627154d4865cf9 Mon Sep 17 00:00:00 2001
From: Megan Marsh <megan@hashicorp.com>
Date: Tue, 19 Jan 2021 15:30:34 -0800
Subject: [PATCH 1/3] enable Packer fmt to read from stdin

---
 command/fmt.go            |  7 +++--
 hcl2template/formatter.go | 60 ++++++++++++++++++++++++++-------------
 2 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/command/fmt.go b/command/fmt.go
index 822d5b3a1..5b15ed772 100644
--- a/command/fmt.go
+++ b/command/fmt.go
@@ -75,8 +75,11 @@ Usage: packer fmt [options] [TEMPLATE]
   configuration files (.pkr.hcl) and variable files (.pkrvars.hcl) are updated.
   JSON files (.json) are not modified.
 
-  If TEMPATE is "." the current directory will be used. The given content must
-  be in Packer's HCL2 configuration language; JSON is not supported.
+  If TEMPATE is "." the current directory will be used.
+  If TEMPATE is "-" then content will be read from STDIN.
+
+  The given content must be in Packer's HCL2 configuration language; JSON is
+  not supported.
 
 Options:
   -check        Check if the input is formatted. Exit status will be 0 if all
diff --git a/hcl2template/formatter.go b/hcl2template/formatter.go
index e6b1c6634..e83974a15 100644
--- a/hcl2template/formatter.go
+++ b/hcl2template/formatter.go
@@ -31,25 +31,33 @@ func NewHCL2Formatter() *HCL2Formatter {
 //
 // Path can be a directory or a file.
 func (f *HCL2Formatter) Format(path string) (int, hcl.Diagnostics) {
-	hclFiles, _, diags := GetHCL2Files(path, hcl2FileExt, hcl2JsonFileExt)
-	if diags.HasErrors() {
-		return 0, diags
-	}
 
-	hclVarFiles, _, diags := GetHCL2Files(path, hcl2VarFileExt, hcl2VarJsonFileExt)
-	if diags.HasErrors() {
-		return 0, diags
-	}
+	var allHclFiles []string
+	var diags []*hcl.Diagnostic
+
+	if path == "-" {
+		allHclFiles = []string{"-"}
+	} else {
+		hclFiles, _, diags := GetHCL2Files(path, hcl2FileExt, hcl2JsonFileExt)
+		if diags.HasErrors() {
+			return 0, diags
+		}
+
+		hclVarFiles, _, diags := GetHCL2Files(path, hcl2VarFileExt, hcl2VarJsonFileExt)
+		if diags.HasErrors() {
+			return 0, diags
+		}
 
-	allHclFiles := append(hclFiles, hclVarFiles...)
+		allHclFiles = append(hclFiles, hclVarFiles...)
 
-	if len(allHclFiles) == 0 {
-		diags = append(diags, &hcl.Diagnostic{
-			Severity: hcl.DiagError,
-			Summary:  fmt.Sprintf("Cannot tell whether %s contains HCL2 configuration data", path),
-		})
+		if len(allHclFiles) == 0 {
+			diags = append(diags, &hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  fmt.Sprintf("Cannot tell whether %s contains HCL2 configuration data", path),
+			})
 
-		return 0, diags
+			return 0, diags
+		}
 	}
 
 	if f.parser == nil {
@@ -80,9 +88,17 @@ func (f *HCL2Formatter) processFile(filename string) ([]byte, error) {
 		f.Output = os.Stdout
 	}
 
-	in, err := os.Open(filename)
-	if err != nil {
-		return nil, fmt.Errorf("failed to open %s: %s", filename, err)
+	var in io.Reader
+	var err error
+
+	if filename == "-" {
+		in = os.Stdin
+		f.ShowDiff = false
+	} else {
+		in, err = os.Open(filename)
+		if err != nil {
+			return nil, fmt.Errorf("failed to open %s: %s", filename, err)
+		}
 	}
 
 	inSrc, err := ioutil.ReadAll(in)
@@ -105,8 +121,12 @@ func (f *HCL2Formatter) processFile(filename string) ([]byte, error) {
 	_, _ = f.Output.Write(s)
 
 	if f.Write {
-		if err := ioutil.WriteFile(filename, outSrc, 0644); err != nil {
-			return nil, err
+		if filename == "-" {
+			f.Output.Write(outSrc)
+		} else {
+			if err := ioutil.WriteFile(filename, outSrc, 0644); err != nil {
+				return nil, err
+			}
 		}
 	}
 

From 40df74e95afca30ba0aa8dbfa50cfd9fdad05d88 Mon Sep 17 00:00:00 2001
From: Megan Marsh <megan@hashicorp.com>
Date: Tue, 19 Jan 2021 15:34:18 -0800
Subject: [PATCH 2/3] linting

---
 hcl2template/formatter.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hcl2template/formatter.go b/hcl2template/formatter.go
index e83974a15..6a3db089b 100644
--- a/hcl2template/formatter.go
+++ b/hcl2template/formatter.go
@@ -122,7 +122,7 @@ func (f *HCL2Formatter) processFile(filename string) ([]byte, error) {
 
 	if f.Write {
 		if filename == "-" {
-			f.Output.Write(outSrc)
+			_, _ = f.Output.Write(outSrc)
 		} else {
 			if err := ioutil.WriteFile(filename, outSrc, 0644); err != nil {
 				return nil, err

From 2b0996daa6acff5e6416857bd934a2f6fbaebb01 Mon Sep 17 00:00:00 2001
From: Megan Marsh <megan@hashicorp.com>
Date: Wed, 20 Jan 2021 11:30:50 -0800
Subject: [PATCH 3/3] dont print filename if its reading from stdin

---
 hcl2template/formatter.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hcl2template/formatter.go b/hcl2template/formatter.go
index 6a3db089b..d02d421a4 100644
--- a/hcl2template/formatter.go
+++ b/hcl2template/formatter.go
@@ -117,8 +117,10 @@ func (f *HCL2Formatter) processFile(filename string) ([]byte, error) {
 		return nil, nil
 	}
 
-	s := []byte(fmt.Sprintf("%s\n", filename))
-	_, _ = f.Output.Write(s)
+	if filename != "-" {
+		s := []byte(fmt.Sprintf("%s\n", filename))
+		_, _ = f.Output.Write(s)
+	}
 
 	if f.Write {
 		if filename == "-" {