feat: add pip printing style

Author: lunte

fext/command/freeze.go

@@ -24,17 +24,17 @@ type Freeze struct {
 func (cmd *Freeze) getPrintFunc() (func(), error) {
 	if cmd.printMode == "human" {
 		return cmd.printStyleHuman, nil
+	} else if cmd.printMode == "pip" {
+		return cmd.printStylePIP, nil
 	} else {
 		return nil, &ferror.UnexpectedMode{Mode: cmd.printMode}
 	}
 }
 
-// printStyleHuman prints a list of packages in a human-readable style, including
-// general info about the number of packages and their weight.
+// printStyleHuman outputs a list of packages in a human-readable style,
+// including general info about the number of packages and their weight.
 //
-// Function ignores packages with an error, which means the error will never be
-// returned. Packages that failed to load will be displayed at the end as a
-// warning line.
+// Packages that failed to load will be displayed at the end as a warning line.
 func (cmd *Freeze) printStyleHuman() {
 	var brokenPackages []string
 	var count int
@@ -66,6 +66,24 @@ func (cmd *Freeze) printStyleHuman() {
 	}
 }
 
+// printStylePIP outputs a list of packages in PIP style, but with comments.
+// Packages that failed to load will be commented out.
+func (cmd *Freeze) printStylePIP() {
+	fmt.Printf(
+		"# This file generated by Fext (%s)\n# Broken packages are commented out\n\n",
+		config.Version,
+	)
+
+	for _, metaDir := range cmd.metaDirectories {
+		p, err := pkg.LoadFromMetaDir(metaDir)
+		if err == nil {
+			fmt.Printf("%s==%s\n", p.Name, p.Version)
+		} else {
+			fmt.Printf("# %s\n", metaDir)
+		}
+	}
+}
+
 // scanMetaDirectories goes through the directory with python modules and
 // packages, selects the meta-directories and appends them to the metaDirectories
 // attribute. Returns an error if the folder could not be read.