Tip: Testing the templates on the fly - go-easygen/easygen GitHub Wiki

Testing the templates on the fly

echo 'Name: some-init-method' > /tmp/var.yaml

$ EASYGEN_TS='{{.Name}}' easygen /tmp/var
some-init-method

$ easygen -ts '{{clk2uc .Name}}' /tmp/var
SomeInitMethod

I.e., with the environment variable EASYGEN_TS or the -ts option on cli, the .tmpl template file is not used.

Here are more examples:

$ EASYGEN_TS='{{.Name}}' easygen -ts '{{clk2uc .Name}}' /tmp/var
SomeInitMethod
# when both `EASYGEN_TS` environment variable and `-ts` option are provided, the latter takes precedence

$ easygen -ts '{{$n := sprintf .Name}} {{$n}}' /tmp/var.yaml
 some-init-method

$ easygen -ts '{{$n := sprintf "%s, %.2f" (clk2uc .Name) 12.3456}} {{$n}}' /tmp/var.yaml
 SomeInitMethod, 12.35

$ easygen -ts '{{substr (clk2uc .Name) 4}}' /tmp/var
InitMethod

$ easygen -ts '{{substr (clk2uc .Name) 8 3}}' /tmp/var
Met

$ easygen -ts '{{substr (clk2uc .Name) 4 -2}}' /tmp/var
InitMeth

$ easygen -ts '{{substr (clk2uc .Name) -6}}' /tmp/var
Method

$ easygen -ts '{{substr "abcde" -3}}' /tmp/var
cde

I.e., command line value takes the highest priority, even overriding the environment variable EASYGEN_TS's value.

As such, if you have a different naming convention than using .tmpl for template file and .yaml for data file, you can override them in environment variables, EASYGEN_ET and EASYGEN_EY, so that you don't need to use -et and/or -ey to override them from command line each time.

echo 'Name: myConstantVariable' > /tmp/var.yml

$ EASYGEN_EY=.yml easygen -ts '{{clc2ss .Name}}' /tmp/var
MY_CONSTANT_VARIABLE

Tips

You can use easygen as an generic Go template testing tool with the -ts commandline option. For example,

echo "Age: 16" > /tmp/age.yaml

$ easygen -ts "{{.Age}}" /tmp/age
16

$ easygen -ts '{{$age := .Age}}{{/* comments allowed but no extra spaces allowed outside comments */}}{{$age}}' /tmp/age
16

$ easygen -ts '{{.Age}} {{ENV "SHELL"}}{{ENV "DISPLAY"}} ({{ENV "NONONO"}})' /tmp/age
16 /bin/bash:0 ()

$ easygen -ts '{{ if eq (ENV "SHELL") "/bin/bash" }}Shell is bash{{end}}; {{ if ne (ENV "DISPLAY") "" }}DISPLAY is set{{end}}' /tmp/age
Shell is bash; DISPLAY is set

$ easygen -ts '{{$underAge := lt .Age 16}}{{ if not $underAge }}toast{{else}}no drinking{{end}}' /tmp/age
toast
# see https://pkg.go.dev/text/template#hdr-Functions

$ easygen -ts '{{ if false }}F{{else if true}}in else if{{end}}' /tmp/age
in else if

$ easygen -ts '{{printf "%x" .Age}}' /tmp/age
10

$ easygen -ts '{{date "Y4"}}' /tmp/age
2017
$ 

$ easygen -ts '{{date "I"}}' /tmp/age
2017-07-10

$ easygen -ts '{{date "."}}' /tmp/age
2017.07.10

$ easygen -ts '{{date ""}}' /tmp/age
20170710

$ easygen -ts '{{timestamp}}' /tmp/age
2017-07-10T08:53:25-04:00

$ easygen -ts '{{timestamp "unix"}}' /tmp/age
1499691221

echo '{FirstName: John, LastName: Doe}' > /tmp/name.yaml

$ easygen -ts '{{ print "Concatenated: " .FirstName "." .LastName }}' /tmp/name.yaml
Concatenated: John.Doe

$ easygen -ts '{{.FirstName}}'\''s full name is {{printf "%s%s" .FirstName .LastName | len}} letters long.' /tmp/name
John's full name is 7 letters long.

$ easygen -ts "{{.FirstName}} {{clk2ss .LastName}}'s full name is "'{{len (printf "%s%s" .FirstName .LastName)}} letters long.' /tmp/name
John DOE's full name is 7 letters long.

$ easygen -ts '{{ $wanted := regexpFindString .FirstName `(?i)^john$` }} {{- if gt (len $wanted) 0 -}} {{.FirstName}} Found!{{end}}' /tmp/name
John Found!

$ easygen -ts '{{ $wanted := regexpFindString .FirstName `(?i)^john$` }} {{- if $wanted -}} {{.FirstName}} Found!{{end}}' /tmp/name
John Found!


echo 'Name: some-init-method' > /tmp/var.yaml

$ easygen -ts '{{.Name}} {{6 | minus1}} {{minus1 6}} {{clk2lc .Name}} {{clk2uc .Name}}' /tmp/var
some-init-method 5 5 someInitMethod SomeInitMethod

# More built-in function examples. See https://github.com/go-easygen/easygen/issues/25
$ easygen -ts '{{stringsContains .Name "init"}}' /tmp/var
true

$ easygen -ts '{{stringsContains .Name "foobar"}}' /tmp/var
false

$ easygen -ts '{{if (stringsContains .Name "init")}}"{{.Name}}" contains "init"{{else}} there {{end}}!' /tmp/var
"some-init-method" contains "init"!

$ easygen -ts '{{if (stringsContains .Name "init")}}"{{.Name}}" splits into: {{range (stringsSplit .Name "-")}}{{.}} {{end}}{{else}} there {{end}}!' /tmp/var
"some-init-method" splits into: some init method !

$ echo 'Name: "%bob'"'"'s file"' | tee /tmp/var.yaml
Name: "%bob's file"

$ easygen -ts '{{quote4shell .Name}}' /tmp/var
'%bob'\''s file'

You can make use any existing test files. E.g., under /path/to/go-easygen/easygen:

$ easygen -ts '{{ regexpReplaceAllString .StrTest "(?i)th[eo]se" "the" }}' test/strings.yaml 
the rights belong to the people

Dealing with missing data

# No missing data

$ easygen -ts '{{ .StrTest }}' test/strings.yaml
These rights belong to those people

$ easygen -ts '{{ coalesce .StrTest "Something else" }}' test/strings.yaml 
These rights belong to those people

$ easygen -ts '{{ coalesce .Colors }}' test/list0.yaml
[red blue white]


# Empty data

$ easygen -ts '"{{ .StrEmpty }}"' test/strings.yaml
""

$ easygen -ts '{{ coalesce .StrEmpty "Something else" }}' test/strings.yaml 
Something else


# Missing data

$ easygen -ts '"{{ .StrNone }}"' test/strings.yaml
"<no value>"

$ easygen -ts '{{ coalesce .StrNone "Not exist" }}' test/strings.yaml
Not exist

$ easygen -ts '{{ coalesce .Description "No description" }}' test/strings.yaml
No description

$ env | grep DISPLAY
DISPLAY=:0

$ easygen -ts '{{ coalesce (ENV "DISPLAY") "0" }}{{ coalesce (ENV "NONONO") "-1" }}' /tmp/age
:0-1

Note,

To fix <no value> in the output cause by the none-exist variables,
I had to use {{if .Var}}{{.Var}}{{else}}No Value{{end}} before. E.g., see "fix <no value>"
With the help of coalesce, it is now much simpler.

Ref

The binary comparison operators

eq
	Returns the boolean truth of arg1 == arg2
ne
	Returns the boolean truth of arg1 != arg2
lt
	Returns the boolean truth of arg1 < arg2
le
	Returns the boolean truth of arg1 <= arg2
gt
	Returns the boolean truth of arg1 > arg2
ge
	Returns the boolean truth of arg1 >= arg2