import sys import yaml with open(sys.argv[1]) as fp: data = fp.read() if not data.find("---") == 0: # no head print("NO YAML HEAD FOUND") sys.exit(-1) data = data[3:] head_end = data.find("---") head = data[0:head_end] data = data[head_end+3:] metadata = yaml.safe_load(head) cats = metadata.pop('categories', None) if cats != None: if type(cats) == list: tags = cats elif type(cats) == str: tags = cats.split() tags = list(map(lambda t: t.lower(), tags)) metadata["tags"] = ", ".join(tags) new_data = f"---\n{yaml.dump(metadata, default_flow_style=False)}---{data}" # write it print(f"coverted: categories to tags: {tags} - {sys.argv[1]}") with open(sys.argv[1], "w") as fp: fp.write(new_data) sys.exit(0) if not metadata.get("tags", None): metadata["tags"] = "untagged" new_data = f"---\n{yaml.dump(metadata, default_flow_style=False)}---{data}" print(f"untagged: {sys.argv[1]}") # write it with open(sys.argv[1], "w") as fp: fp.write(new_data) sys.exit(0) print("No changes needed")
2.2 KiB
comments | date | layout | tags | title |
---|---|---|---|---|
true | 2016-01-14 21:13 | post | go | go: `:=` operator causes accidental shadowing |
Go provides :=
operator to make declaring variables easier. It is a shorthand to declare and set a value of a variable. for example,
var x int
x = 42
can be written as
x := 42
But if not careful, this can accidently shadow variable bindings. Let's look at the fictitious piece of code.
package main
import "fmt"
func fictitiousFunc() (int, error) {
return 42, nil
}
func main() {
x := 10;
x, err := fictitiousFunc()
if err != nil {
fmt.Println("I'll never print")
}
fmt.Println("value of x: ", x)
}
This produces following output
value of x: 42
While, this following piece of code will fail to compile
package main
import "fmt"
func fictitiousFunc() (int, error) {
return 42, nil
}
func main() {
x := 10
// replace :=
var x int
var err error
x, err = fictitiousFunc()
if err != nil {
fmt.Println("I'll never print")
}
fmt.Println("value of x: ", x)
}
output:
prog.go:12: x redeclared in this block
previous declaration at prog.go:10
So we can see that the operator is somewhat intelligent, and does not redeclare the variables.
Now what if we push it down a scope? See the following code
package main
import "fmt"
func fictitiousFunc() (int, error) {
return 42, nil
}
func main() {
someCondition := true
x := -1;
if someCondition {
x, err := fictitiousFunc()
if err != nil {
fmt.Println("I'll never print")
}
fmt.Println("value of x inside: ", x)
}
fmt.Println("value x outside: ", x)
}
This produces,
value of x inside: 42
value x outside: -1
At line: 16, since the immediate scope (line:15-32) does not have variable x
declared, :=
is redeclaring the variable. a.k.a the variable x
gets shadowed.
Only workaround I can think of is not to use :=
, i.e change the code to
if someCondition {
var err error
x, err = fictitiousFunc()
if err != nil {
fmt.Println("I'll never print")
}
fmt.Println("value of x inside: ", x)
}
If you know something better let me know.