58b20109cf
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
| 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.