Lock files for dependency integrity in Deno - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a lock file when running a Deno script.

Deno

deno run --lock=[1] script.ts

Drag options to blanks, or click blank then click option'

Alockfile.txt

Block.json

Cdeno.lock

Ddeps.lock

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lock file name that Deno does not recognize.

Forgetting to specify the lock file name with --lock.

The default lock file name in Deno is deno.lock. Using --lock=deno.lock tells Deno to use this file for dependency integrity.

2fill in blank

medium

Complete the command to create or update the lock file with all dependencies.

Deno

deno run --lock=[1] --lock-write script.ts

Drag options to blanks, or click blank then click option'

Adeno.lock

Block.json

Cdeps.lock

Dlockfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong lock file name.

Not including the --lock-write flag to update the lock file.

Using --lock=deno.lock with --lock-write tells Deno to create or update the deno.lock file with the current dependencies.

3fill in blank

hard

Fix the error in the command to run a script using the lock file without updating it.

Deno

deno run --lock=[1] script.ts

Drag options to blanks, or click blank then click option'

Adeno.lock

Bdeps.lock

Clock.json

Dlockfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using --lock-write when you want to only verify dependencies.

Using a wrong lock file name.

To run a script using the lock file without updating it, use --lock=deno.lock but do not include --lock-write. The presence of --lock-write updates the lock file, which is not desired here.

4fill in blank

hard

Fill both blanks to import a remote module and ensure its integrity with a lock file.

Deno

import [1] from "https://deno.land/std@0.177.0/fs/[2].ts";

Drag options to blanks, or click blank then click option'

AcopyFile

Bcopy

Ccopy_file

Dcopyfile

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect casing for the function name.

Using wrong file name format in the URL.

The correct function name is copyFile and the file name in the URL is copy_file.ts. This matches the Deno standard library naming.

5fill in blank

hard

Fill all three blanks to run a Deno script with a lock file, check integrity, and specify permissions.

Deno

deno run [1] [2] [3] script.ts

Drag options to blanks, or click blank then click option'

A--lock=deno.lock

B--allow-read

C--lock-only

D--allow-net

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up permission flags.

Forgetting to specify the lock file.

Use --lock=deno.lock to specify the lock file, --lock-only to check dependencies without running, and --allow-read to grant read permissions.

Practice

1. What is the main purpose of a lock file in a Deno project?

easy

A. To list all available Deno commands

B. To speed up the execution of Deno scripts

C. To save exact versions of dependencies for consistent builds

D. To store environment variables securely

Solution

1. Step 1: Understand what a lock file does

   A lock file records the exact versions and hashes of dependencies used in a project to ensure consistency.

2. Step 2: Identify the purpose in Deno context

   In Deno, the lock file prevents unexpected changes by locking dependency versions during installs and runs.

3. Final Answer:

   To save exact versions of dependencies for consistent builds -> Option C

4. Quick Check:

   Lock file = exact dependency versions [OK]

Hint: Lock files keep dependencies stable and consistent [OK]

Common Mistakes:

• Thinking lock files speed up script execution
• Confusing lock files with environment variable storage
• Assuming lock files list commands

2. Which Deno command option is used to create or update a lock file?

easy

A. --unstable

B. --lock

C. --reload

D. --lock-write

Solution

1. Step 1: Identify command options related to lock files

   --lock is used to specify a lock file to use, but does not create or update it.

2. Step 2: Understand which option writes the lock file

   --lock-write tells Deno to create or update the lock file with current dependencies.

3. Final Answer:

   --lock-write -> Option D

4. Quick Check:

   Update lock file = --lock-write [OK]

Hint: Use --lock-write to create or update lock files [OK]

Common Mistakes:

• Using --lock alone to update lock files
• Confusing --reload with lock file creation
• Thinking --unstable manages lock files

3. Given the command deno run --lock=lock.json --unstable app.ts, what will happen if lock.json is missing?

medium

A. Deno will throw an error and refuse to run

B. Deno will create a new lock.json automatically

C. Deno will run the script but ignore dependencies

D. Deno will run the script without checking the lock file

Solution

1. Step 1: Understand the --lock option behavior

   Using --lock requires the specified lock file to exist; otherwise, Deno refuses to run to ensure integrity.

2. Step 2: Check what happens if the lock file is missing

   If lock.json is missing, Deno throws an error and stops execution to prevent unverified dependencies.

3. Final Answer:

   Deno will throw an error and refuse to run -> Option A

4. Quick Check:

   Missing lock file + --lock = error [OK]

Hint: --lock requires existing file; missing file causes error [OK]

Common Mistakes:

• Assuming Deno creates lock file automatically
• Thinking Deno ignores missing lock files
• Confusing --lock with --lock-write behavior

4. You run deno run --lock=lock.json app.ts but get an error about a missing lock file. What is the best way to fix this?

medium

A. Delete the lock.json file and rerun the command

B. Run deno run --lock=lock.json --lock-write app.ts to create the lock file

C. Remove the --lock option from the command

D. Run deno cache app.ts without any lock options

Solution

1. Step 1: Identify cause of error

   The error occurs because the specified lock file does not exist yet.

2. Step 2: Use correct command to create lock file

   Adding --lock-write creates or updates the lock file while running the script.

3. Final Answer:

   Run deno run --lock=lock.json --lock-write app.ts to create the lock file -> Option B

4. Quick Check:

   Create lock file with --lock-write [OK]

Hint: Add --lock-write to create missing lock file [OK]

Common Mistakes:

• Deleting lock file instead of creating it
• Removing --lock option and losing integrity
• Running cache without lock options

5. You want to ensure your team uses the exact same dependencies in production and development. Which practice with lock files is best?

hard

A. Commit the lock file to version control and use --lock on all runs

B. Generate a new lock file on each developer machine separately

C. Ignore the lock file and rely on latest versions always

D. Use --lock-write only in production, not in development

Solution

1. Step 1: Understand team consistency needs

   To keep dependencies consistent, everyone must use the same locked versions.

2. Step 2: Identify best lock file usage practice

   Committing the lock file to version control and using --lock ensures all environments use identical dependencies.

3. Final Answer:

   Commit the lock file to version control and use --lock on all runs -> Option A

4. Quick Check:

   Share lock file + use --lock = consistent deps [OK]

Hint: Commit lock file and use --lock for team consistency [OK]

Common Mistakes:

• Generating separate lock files causing version drift
• Ignoring lock files and risking inconsistent builds
• Using --lock-write only in production causing mismatch