{"record":{"id":"e06ba3ed32194d29","repo":"hashicorp/packer","slug":"failed-to-interpolate-s-please-make-sure-that-th","errorCode":null,"errorMessage":"Failed to interpolate %s: Please make sure that the variable you're referencing has been defined; Packer treats all variables used to interpolate other user variables as required.","messagePattern":"Failed to interpolate (.+?): Please make sure that the variable you're referencing has been defined; Packer treats all variables used to interpolate other user variables as required\\.","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"packer/core.go","lineNumber":1040,"sourceCode":"\t\tif !shouldRetry {\n\t\t\tbreak\n\t\t}\n\n\t\t// Clear completed vars from sortedMap before next loop. Do this one\n\t\t// key at a time because the indices are gonna change ever time you\n\t\t// delete from the map.\n\t\tfor _, k := range deleteKeys {\n\t\t\tfor ind, kv := range sortedMap {\n\t\t\t\tif kv.Key == k {\n\t\t\t\t\tsortedMap = append(sortedMap[:ind], sortedMap[ind+1:]...)\n\t\t\t\t\tbreak\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\t}\n\n\tif !changed && shouldRetry {\n\t\treturn ctx, fmt.Errorf(\"Failed to interpolate %s: Please make sure that \"+\n\t\t\t\"the variable you're referencing has been defined; Packer treats \"+\n\t\t\t\"all variables used to interpolate other user variables as \"+\n\t\t\t\"required.\", failedInterpolation)\n\t}\n\n\treturn ctx, nil\n}\n\nfunc (c *Core) init() error {\n\tif c.variables == nil {\n\t\tc.variables = make(map[string]string)\n\t}\n\t// Go through the variables and interpolate the environment and\n\t// user variables\n\tctx, err := c.renderVarsRecursively()\n\tif err != nil {\n\t\treturn err\n\t}","sourceCodeStart":1022,"sourceCodeEnd":1058,"githubUrl":"https://github.com/hashicorp/packer/blob/eb36e3c3e48a036f3e8cc94087636ee72e1303c9/packer/core.go#L1022-L1058","documentation":"When a variable's default references another user variable that is not yet defined (`{{user `other`}}`), `renderVarsRecursively` retries up to 100 loops hoping the dependency resolves. If a pass completes with no variable changed (`!changed`) while some still need interpolation (`shouldRetry`), the reference can never be satisfied, and Packer aborts with this message, embedding the last failed `\"key\": \"value\"` pair. Packer deliberately treats variables used to interpolate other variables as required — they must exist somewhere (defaults, -var, var-file).","triggerScenarios":"During `Core.init()`, variable A's value contains `{{user `B`}}`, B has no default and was not passed via `-var`/`-var-file`/environment, all retries exhaust without progress, so the `!changed && shouldRetry` branch returns the error with `failedInterpolation` showing the unresolved variable.","commonSituations":"Cyclical variable definitions (A references B, B references A); a typo in the referenced variable name so it doesn't match any defined variable; forgetting to pass a required dependency variable on the CLI or in the var-file; renaming a variable but not updating references to it; deep nesting exceeding the 100-iteration cap.","solutions":["Give the referenced variable a `default` value in the template's variables block.","Pass the missing variable at invocation: `packer build -var 'missing=value' ...` or add it to your var-file.","Check the failed `\"key\": \"value\"` text in the error for a misspelled variable name inside `{{user `...`}}` and fix it.","Look for cycles where two variables reference each other and break the loop by inlining a literal value."],"exampleFix":"// before\n\"variables\": {\n  \"ami_name\": \"{{user `env`}}-web-{{timestamp}}\"\n}\n// after (provide 'env' or give it a default)\n\"variables\": {\n  \"env\": {\"default\": \"dev\"},\n  \"ami_name\": \"{{user `env`}}-web-{{timestamp}}\"\n}","handlingStrategy":"try-catch","validationCode":"// verify every {{user `x`}} reference resolves to a defined or provided variable\nfor name, val := range variables {\n    for _, ref := range userRefs(val) { // regex: {{\\s*user\\s*`(.*)`\\s*}}\n        if _, ok := providedVars[ref]; !ok {\n            if v, ok := templateVars[ref]; !ok || v.Default == \"\" && v.Required {\n                return fmt.Errorf(\"variable %s references undefined %s\", name, ref)\n            }\n        }\n    }\n}","typeGuard":null,"tryCatchPattern":"// Go: detect unresolved variable references\nif err := core.Initialize(); err != nil {\n    if strings.Contains(err.Error(), \"Failed to interpolate\") {\n        return fmt.Errorf(\"missing user variable for interpolation: %w\", err)\n    }\n    return err\n}","preventionTips":["Give every referenced variable a default unless it is intentionally required.","Grep templates for `{{user ` before renaming/removing variables to update all references.","Use `packer validate` with the same var-files as the real build to catch missing dependencies early.","Avoid cyclic variable definitions; draw the dependency chain if variables nest more than a couple of levels."],"tags":["packer","interpolation","variables","recursion"],"backgroundTag":"undefined-user-variable","analyzedSha":"eb36e3c3e48a036f3e8cc94087636ee72e1303c9","analyzedAt":"2026-09-05T13:20:43.127Z","contentChangedAt":"2026-09-05T13:20:43.127Z","schemaVersion":2},"datasetVersion":"2026-09-12T17:17:11.597Z"}