Unable to parse YAML: mapping values are not allowed here

Question

Good morning. I'm migrating from Gitlab to CircleCI and try to map out a simple pipeline ("workflow") that basically should look like this:

[build] -> [tests] -> [release*]
* only on tags

I wasted endless hours literally copy-pasting example configs from the documentation. I defined three jobs:

1. build
2. tests
3. release

And I created a minimal workflow that just echos the job title, includes some requires (to map the pipeline) and have a condition that only triggers releases on tags.

However, I always get a YAML parsing error:

#!/bin/sh -eo pipefail
# Unable to parse YAML
# mapping values are not allowed here
#  in 'string', line 25, column 19:
#               requires:
#                       ^
# 
# -------
# Warning: This configuration was auto-generated to show you the message above.
# Don't rerun this job. Rerunning will have no effect.
false

Exited with code 1

This is my config.yaml that currently fails:

version: 2
jobs:
  build:
    steps:
      - run:
          name: Compile Binaries
          command: echo "Compile Binaries"
  tests:
    steps:
      - run:
          name: Run All Tests
          command: echo "Run All Tests"
  build:
    steps:
      - run:
          name: Release Artifacts
          command: echo "Release Artifacts"

workflows:
  version: 2
  minimal:
    jobs:
      - build
      - tests
          requires:
            - build
      - release
          requires:
            - tests
          filters:
            tags:
              only: /^v.*$/

I also tried online YAML validators but they always say this is valid YAML, so something is wrong with the way Circle expects the config to be. What could it be?

---

Edit: I managed to even minify the example that causes the exact same error:

jobs:
  build:
    steps:
      - run:
          name: Release Artifacts
          command: echo "Release Artifacts"

workflows:
  minimal:
    jobs:
      - release
          filters:
            tags:
              only: /^v.*$/

Causes:

#!/bin/sh -eo pipefail
# Unable to parse YAML
# mapping values are not allowed here
#  in 'string', line 12, column 18:
#               filters:
#                      ^
# 
# -------
# Warning: This configuration was auto-generated to show you the message above.
# Don't rerun this job. Rerunning will have no effect.
false

Exited with code 1

Answer 1

Running your config.yml through yamllint, produced the following:

  1:1       warning  missing document start "---"  (document-start)
  13:3      error    duplication of key "build" in mapping  (key-duplicates)
  25:19     error    syntax error: mapping values are not allowed here

When I add colons to the entry on lines 25 and 28:

workflows:
  version: 2
  minimal:
    jobs:
      - build
      - tests:
          requires:
            - build
      - release:
          requires:
            - tests
          filters:
            tags:
              only: /^v.*$/

...the syntax error is no longer reported:

1:1       warning  missing document start "---"  (document-start)  
13:3      error    duplication of key "build" in mapping (key-duplicates)

Answer 2

You simply have an incorrect yaml syntax in your workflows jobs list.

From what I could very quickly understand on circleCI's documentation, jobs names are accepted as a shorthand if you don't define any parameters. If you have parameters, the list element is a hashmap with top element being the job name. In your specific case, this should give (note the column after the names of jobs with params):

workflows:
  version: 2
  minimal:
    jobs:
      - build
      - tests:
          requires:
            - build
      - release:
          requires:
            - tests
          filters:
            tags:
              only: /^v.*$/