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Create Editor To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments

GitLab Flavored Markdown (GLFM) Specification Guide (FREE)

GitLab supports Markdown in various places. The Markdown dialect we use is called GitLab Flavored Markdown, or GLFM.

The specification for the GLFM dialect is based on the GitHub Flavored Markdown (GFM) specification, which is in turn based on the CommonMark specification. The GLFM specification includes several extensions to the GFM specification.

See the section on acronyms for a detailed explanation of the various acronyms used in this document. This guide is a developer-facing document that describes the various terms and definitions, goals, tools, and implementations related to the GLFM specification. It is intended to support and augment the user-facing documentation for GitLab Flavored Markdown.

NOTE: In this document, GFM refers to GitHub Flavored Markdown, not GitLab Flavored Markdown. Refer to the section on acronyms for a detailed explanation of the various acronyms used in this document.

NOTE: This guide and the implementation and files described in it are still a work in progress. As the work progresses, rewrites and consolidation between this guide and the user-facing documentation for GitLab Flavored Markdown are likely.

Terms and definitions

Acronyms: GLFM, GHFM, GFM, CommonMark

GitHub Flavored Markdown is widely referred to by the acronym GFM, and this document follows that convention as well. GitLab Flavored Markdown is referred to as GLFM in this document, to distinguish it from GitHub Flavored Markdown.

Unfortunately, this convention is not followed consistently in the rest of the documentation or GitLab codebase. In many places, the GFM acronym is used to refer to GitLab Flavored Markdown. An open issue exists to resolve this inconsistency.

Some places in the code refer to both the GitLab and GitHub specifications simultaneous in the same areas of logic. In these situations, GitHub Flavored Markdown may be referred to with variable or constant names like ghfm_ to avoid confusion. For example, we use the ghfm acronym for the ghfm_spec_v_0.29.txt GitHub Flavored Markdown specification file which is committed to the gitlab repo and used as input to the update_specification.rb script.

The original CommonMark specification is referred to as CommonMark (no acronym).

Various Markdown specifications

The specification format we use is based on the approach used in CommonMark, where a spec.txt file serves as documentation, as well as being in a format that can serve as input to automated conformance tests. It is explained in the CommonMark specification:

This document attempts to specify Markdown syntax unambiguously. It contains many examples with side-by-side Markdown and HTML. These examples are intended to double as conformance tests.

Here are the HTML-rendered versions of the specifications:

NOTE: The creation of the GitLab Flavored Markdown (GLFM) specification file is still pending.

However, GLFM has more complex parsing, rendering, and testing requirements than GFM or CommonMark. Therefore, it does not have a static, hardcoded, manually updated spec.txt. Instead, the GLFM spec.txt is automatically generated based on other input files. This process is explained in detail in the Implementation sections below.

Markdown examples

Everywhere in the context of the specification and this guide, the term examples is specifically used to refer to the Markdown + HTML pairs used to illustrate the canonical parsing (or rendering) behavior of various Markdown source strings in the standard CommonMark specification format.

In this context, it should not be confused with other similar or related meanings of example, such as RSpec examples.

Parsers and renderers

To understand the various ways in which a specification is used, and how it related to a given Markdown dialect, it's important to understand the distinction between a parser and a renderer:

  • A Markdown parser accepts Markdown as input and produces a Markdown Abstract Syntax Tree (AST) as output.
  • A Markdown renderer accepts the AST produced by a parser, and produces HTML (or a PDF, or any other relevant rendering format) as output.

Types of Markdown tests driven by the GLFM specification

The two main types of automated testing are driven by the Markdown examples and data contained in the GLFM specification. We refer to them as:

  • Markdown conformance testing.
  • Markdown snapshot testing.

Many other types of tests also occur in the GitLab codebase, and some of these tests are also related to the GLFM Markdown dialect. Therefore, to avoid confusion, we use these standard terms for the two types of specification-driven testing referred to in this documentation and elsewhere.

Markdown conformance testing

Markdown conformance testing refers to the standard testing method used by all CommonMark Markdown dialects to verify that a specific implementation conforms to the CommonMark Markdown specification. It is enforced by running the standard CommonMark tool spec_tests.py against a given spec.txt specification and the implementation.

NOTE: spec_tests.py may eventually be re-implemented in Ruby, to not have a dependency on Python.

Markdown snapshot testing

Markdown snapshot testing refers to the automated testing performed in the GitLab codebase, which is driven by snapshot fixture data derived from the GLFM specification. It consists of both backend RSpec tests and frontend Jest tests which use the fixture data. This fixture data is contained in YAML files. These files can be generated and updated based on the Markdown examples in the specification, and the existing GLFM parser and render implementations. They may also be manually updated as necessary to test-drive incomplete implementations. Regarding the terminology used here:

  1. The Markdown snapshot tests can be considered a form of the Golden Master Testing approach, which is also referred to as Approval Testing or Characterization Testing.
    1. The term Golden Master originally comes from the recording industry, and refers to the process of mastering, or making a final mix from which all other copies are produced.
    2. For more information and background, you can read about Characterization Tests and Golden Masters.
  2. The usage of the term snapshot does not refer to the approach of Jest snapshot testing, as used elsewhere in the GitLab frontend testing suite. However, the Markdown snapshot testing does follow the same philosophy and patterns as Jest snapshot testing:
    1. Snapshot fixture data is represented as files which are checked into source control.
    2. The files can be automatically generated and updated based on the implementation of the code under tests.
    3. The files can also be manually updated when necessary, for example, to test-drive changes to an incomplete or buggy implementation.
  3. The usage of the term fixture does not refer to standard Rails database fixture files. It instead refers to test fixtures in the more generic definition, as input data to support automated testing. However, fixture files still exist, so they are colocated under the spec/fixtures directory with the rest of the fixture data for the GitLab Rails application.

See also the section on normalization below, which is an important concept used in the Markdown snapshot testing.

Parsing and Rendering

The Markdown dialect used in the GitLab application has a dual requirement for rendering:

  1. Rendering to static read-only HTML format, to be displayed in various places throughout the application.
  2. Rendering editable content in the Content Editor, a "What You See Is What You Get" (WYSIWYG) editor. The Content Editor supports real-time instant switching between an editable Markdown source and an editable WYSIWYG document.

These requirements means that GitLab has two independent parser and renderer implementations:

  1. The backend parser / renderer supports parsing and rendering to static read-only HTML. It is implemented in Ruby. It leverages the commonmarker gem, which is a Ruby wrapper for libcmark-gfm, GitHub's fork of the reference parser for CommonMark. libcmark-gfm is an extended version of the C reference implementation of CommonMark
  2. The frontend parser / renderer supports parsing and WYSIWYG rendering for the Content Editor. It is implemented in JavaScript. Parsing is based on the Remark Markdown parser, which produces a MDAST Abstract Syntax Tree (MDAST). Rendering is the process of turning an MDAST into a ProseMirror document. Then, ProseMirror is used to render a ProseMirror document to WYSIWYG HTML. In this document, we refer to the process of turning Markdown into an MDAST as the frontend / JavaScript parser, and the entire process of rendering Markdown to WYSIWYG HTML in ProseMirror as the Content Editor. Several requirements drive the need for an independent frontend parser / renderer implementation, including:
    1. Lack of necessary support for accurate source mapping in the HTML renderer implementation used on the backend.
    2. Latency and bandwidth concerns: eliminating the need for a round-trip to the backend every time the user switches between the Markdown source and the WYSIWYG document.
    3. Different HTML and browser rendering requirements for WYSIWYG documents. For example, displaying read-only elements such as diagrams and references in an editable form.

Multiple versions of rendered HTML

Both of these GLFM renderer implementations (static and WYSIWYG) produce HTML which differs from the canonical HTML examples from the specification. For every Markdown example in the GLFM specification, three versions of HTML can potentially be rendered from the example:

  • Static HTML.
  • WYSIWYG HTML.
  • Canonical HTML.

Static HTML

Static HTML is HTML produced by the backend (Ruby) renderer, which contains extra styling and behavioral HTML. For example, Create task buttons added for dynamically creating an issue from a task list item. The GitLab Markdown API generates HTML for a given Markdown string using this method.

WYSIWYG HTML

WYSIWYG HTML is HTML produced by the frontend (JavaScript) Content Editor, which includes parsing and rendering logic. It is used to present an editable document in the ProseMirror WYSIWYG editor.

Canonical HTML

Canonical HTML is the clean, basic version of HTML rendered from Markdown.

  1. For the examples which come from the CommonMark specification and GFM extensions specification, the canonical HTML is the exact identical HTML found in the GFM spec.txt example blocks.
  2. For GLFM extensions to the GFM / CommonMark specification, a glfm_canonical_examples.txt input specification file contains the Markdown examples and corresponding canonical HTML examples.

Canonicalization of HTML

The rendered static HTML and WYSIWYG HTML from the backend (Ruby) and frontend (JavaScript) renderers usually contains extra styling or HTML elements, to support specific appearance and behavioral requirements.

Neither the backend nor the frontend rendering logic can directly render the clean, basic canonical HTML. Nor should they be able to, because:

  • It's not a direct requirement to support any GitLab application feature.
  • Adding this feature adds unnecessary requirements and complexity to the implementations.

Instead, the rendered static or WYSIWYG HTML is converted to canonical HTML by a canonicalization process. This process can strip all the extra styling and behavioral HTML from the static or WYSIWYG HTML, resulting in canonical HTML which exactly matches the Markdown + HTML examples in a standard spec.txt specification.

Use the canonicalize-html.rb script for this process. More explanation about this canonicalization process in the sections below.

NOTE: Some of the static or WYSIWYG HTML examples may not be representable as canonical HTML. (For example, when they are represented as an image.) In these cases, the Markdown conformance test for the example can be skipped by setting skip_update_example_snapshots: true for the example in glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml.

Normalization

Versions of the rendered HTML and ProseMirror JSON can vary for a number of reasons. Differences in styling or HTML structure can occur, but the values of attributes or nodes may also vary across different test runs or environments. For example:

  1. Database record identifiers
  2. Namespace or project identifiers
  3. Portions of URIs
  4. File paths or names
  5. Random values

For the Markdown snapshot testing to work properly, you must account for these differences in a way that ensures the tests are reliable, and always behave the same across different test runs or environments.

To account for these differences, there is a process called normalization. Normalization allows custom regular expressions with capturing groups to be applied to two different versions of HTML or JSON for a given Markdown example, and the contents of the captured groups can be replaced with the same fixed values.

Then, the two normalized versions can be compared to each other to ensure all other non-variable content is identical.

NOTE: We don't care about verifying specific attribute values here, so it's OK if the normalizations discard and replace these variable values with fixed values. Different testing levels have different purposes:

  1. Markdown snapshot testing is intended to enforce the structure of the rendered HTML/JSON, and to ensure that it conforms to the canonical specification.
  2. Individual unit tests of the implementation for a specific Markdown example are responsible for specific and targeted testing of these variable values.

We also use this same regex capture-and-replace normalization approach for canonicalization of HTML, because it is essentially the same process. With canonicalization, instead of just replacing variable values, we are removing non-canonical portions of the HTML.

Refer to glfm_example_normalizations.yml for a detailed explanation of how the normalizations are specified.

Goals

Given the constraints above, we have a few goals related to the GLFM specification and testing infrastructure:

  1. A canonical spec.txt exists, and represents the official specification for GLFM, which meets these requirements:

    1. The spec is a strict superset of the GitHub Flavored Markdown (GFM) specification, just as GFM is a strict superset of the CommonMark specification. Therefore, it contains the superset of all canonical Markdown + HTML examples for CommonMark, GFM, and GLFM.
    2. It contains a prose introduction section which is specific to GitLab and GLFM.
    3. It contains all other non-introduction sections verbatim from the GFM spec.txt.
    4. It contains a new extra section for the GLFM GitLab-specific extensions, with both prose and examples describing the extensions.
    5. It should be in the standard format which can processed by the standard CommonMark tools spec_tests.py, which is a script used to run the Markdown conformance tests against all examples contained in a spec.txt.

  2. The GLFM parsers and HTML renderers for both the static backend (Ruby) and WYSIWYG frontend (JavaScript) implementations support consistent rendering of all canonical Markdown + HTML examples in the GLFM spec.txt specification, as verified by spec_tests.py.

    NOTE: Consistent does not mean that both of these implementations render to the identical HTML. They each have different implementation-specific additions to the HTML they render, so therefore their rendered HTML is "canonicalized" to canonical HTML prior running the Markdown conformance tests.

  3. For both the static backend (Ruby) and WYSIWYG frontend (JavaScript) implementations, a set of example snapshots exists in the form of YAML files, which correspond to every Markdown example in the GLFM spec.txt. These example snapshots support the following usages for every GLFM Markdown example:

    1. The backend (Ruby) parser and renderer can convert Markdown to the expected custom static HTML.
    2. The frontend (JavaScript) parser and renderer (which includes GitLab custom code and Remark) can convert Markdown to the expected ProseMirror JSON representing a ProseMirror document.
    3. The Content Editor (which includes the frontend (JavaScript) parser and renderer, and ProseMirror) can convert Markdown to the expected custom WYSIWYG HTML as rendered by ProseMirror.
    4. The Content Editor can complete a round-trip test, which involves converting from Markdown, to MDAST, to ProseMirror Document, then back to Markdown. It ensures the resulting Markdown is exactly identical, with no differences.

Implementation

The following set of scripts and files is complex. However, it allows us to meet all of the goals listed above, and is carefully designed to meet the following implementation goals:

  1. Minimize the amount of manual editing, curation, and maintenance of the GLFM specification and related files.
  2. Automate and simplify the process of updating the GLFM specification and related files when there are changes to the upstream CommonMark spec, GFM extensions, or the GLFM extensions.
  3. Support partial or incomplete implementations of the GLFM specification, whether due to in-progress work, bugs, or new future Markdown support, while still performing all functionality for the existing implementations.
  4. Automate, simplify, and support running various tests, including the standard CommonMark conformance tests and GLFM-implementation-specific unit/acceptance Markdown snapshot tests.
  5. Provide a rich set of extensible metadata around all GLFM specification examples to support current and future requirements, such as automated acceptance testing and automated documentation updates.

The documentation on the implementation is split into three sections:

  1. Scripts.
  2. Specification files.
  3. Example snapshot files: These YAML files are used as input data or fixtures to drive the various tests, and are located under spec/fixtures/glfm/example_snapshots. All example snapshot files are automatically generated based on the specification files and the implementation of the parsers and renderers. However, they can also be directly edited if necessary, such as to test-drive an incomplete implementation.

Scripts

These executable scripts perform various tasks related to maintaining the specification and running tests. Each script has a shell-executable entry point file located under scripts/glfm, but the actual implementation is in unit-tested classes under scripts/lib/glfm.

NOTE: Some of these scripts are implemented in Ruby, and others are shell scripts. Ruby scripts are used for more complex custom scripts, to enable easier unit testing and debugging. Shell scripts are used for simpler scripts which primarily invoke other shell commands, to avoid the challenges related to running other shell sub-processes from Ruby scripts.

NOTE: The Ruby executable scripts under scripts/glfm have dashes instead of underscores in the filenames. This naming is non-standard for a Ruby file, but is used to distinguish them from the corresponding implementation class entry point files under scripts/lib/glfm when searching by filename.

update-specification.rb script

The scripts/glfm/update-specification.rb script uses specification input files to generate and update spec.txt (Markdown) and spec.html (HTML). The spec.html is generated by passing the generated (or updated) spec.txt Markdown to the backend API for rendering to static HTML:

graph LR
subgraph script:
  A{update-specification.rb}
  A --> B{Backend Markdown API}
end
subgraph input:<br/>input specification files
  C[ghfm_spec_v_0.29.txt] --> A
  D[glfm_intro.txt] --> A
  E[glfm_canonical_examples.txt] --> A
end
subgraph output:<br/>GLFM specification files
  A --> F[spec.txt]
  F --> B
  B --> G[spec.html]
end

canonicalize-html.rb script

The scripts/glfm/canonicalize-html.rb handles the "canonicalization" of HTML. It is a pipe-through helper script which takes as input a static or WYSIWYG HTML string containing extra HTML, and outputs a canonical HTML string.

It is implemented as a standalone, modular, single-purpose script, based on the Unix philosophy. It's easy to use when running the standard CommonMark spec_tests.py script, which expects canonical HTML, against the GitLab renderer implementations.

run-spec-tests.sh script

scripts/glfm/run-spec-tests.sh is a convenience shell script which runs conformance specs via the CommonMark standard spec_tests.py script, which uses the glfm_specification/output/spec.txt file and scripts/glfm/canonicalize-html.rb helper script to test the GLFM renderer implementations' support for rendering Markdown specification examples to canonical HTML.

graph LR
subgraph scripts:
  A{run-spec-tests.sh} --> C
  subgraph specification testing process
    B[canonicalize-html.sh] --> C
    C[spec_tests.py]
  end
end
subgraph input
  D[spec.txt GLFM specification] --> C
  E((GLFM static<br/>renderer implementation)) --> B
  F((GLFM WYSIWYG<br/>renderer implementation)) --> B
end
subgraph output:<br/>test results/output
  C --> G[spec_tests.py output]
end

update-example-snapshots.rb script

The scripts/glfm/update-example-snapshots.rb script uses the GLFM glfm_specification/output/spec.txt specification file and the glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml file to create and update the example snapshot YAML files:

graph LR
subgraph script:
  A{update-example-snapshots.rb}
end
subgraph input:<br/>input specification file
  B[spec.txt] --> A
  C[glfm_example_status.yml] --> A
end
subgraph output:<br/>example snapshot files
  A --> E[examples_index.yml]
  A --> F[markdown.yml]
  A --> G[html.yml]
  A --> H[prosemirror_json.yml]
end

run-snapshot-tests.sh script

The scripts/glfm/run-snapshot-tests.sh convenience shell script runs all relevant Markdown snapshot testing RSpec and Jest *_spec files (from main app spec folder) which are driven by example_snapshot YAML files.

The actual RSpec and Jest test *_spec files (frontend and backend) live under the normal relevant locations under spec, matching the location of their corresponding implementations. They can be run either:

  • As part of the normal pipelines.
  • From the command line or an IDE, just like any other file under spec.

However, they are spread across four different locations:

  • Backend tests under spec/requests.
  • Backend EE tests under ee/spec/requests.
  • Frontend tests under spec/frontend.
  • Frontend EE tests under ee/spec/frontend.

Therefore, this convenience script is intended to only be used in local development. It simplifies running all tests at once and returning a single return code. It contains only shell scripting commands for the relevant bundle exec rspec ... and yarn jest ... commands.

graph LR
subgraph tests:
  B[relevant rspec+jest test files]
end
subgraph script:
  A{run-snapshopt-tests.sh} -->|invokes| B
end
subgraph input:<br/>YAML
  C[examples_index.yml] --> B
  D[markdown.yml] --> B
  E[html.yml] --> B
  F[prosemirror_json.yml] --> B
end
subgraph output:<br/>test results/output
  B --> H[rspec+jest output]
end

Specification files

These files represent the GLFM specification itself. They are all located under the root glfm_specification, and are further divided into two subfolders:

  • input: Contains files which are imported or manually edited.
  • output: Contains files which are automatically generated.

Input specification files

The glfm_specification/input directory contains files which are the original input to drive all other automated GLFM specification scripts/processes/tests. They are either downloaded, as in the case of the GFM spec.txt file, or manually updated, as in the case of all GFM files.

GitHub Flavored Markdown specification

glfm_specification/input/github_flavored_markdown/ghfm_spec_v_0.29.txt is the official latest GFM spec.txt.

  • It is automatically downloaded and updated by update-specification.rb script.
  • When it is downloaded, the version number is added to the filename.

NOTE: This file uses the ghfm acronym instead of gfm, as explained in the Acronyms section.

glfm_intro.txt

glfm_specification/input/gitlab_flavored_markdown/glfm_intro.txt is the GitLab-specific version of the prose in the introduction section of the GLFM specification.

  • It is manually updated.
  • The update-specification.rb script inserts it into the generated GLFM spec.txt to replace the GitHub-specific GFM version of the introductory section.
glfm_canonical_examples.txt

glfm_specification/input/gitlab_flavored_markdown/glfm_canonical_examples.txt is the manually updated canonical Markdown+HTML examples for GLFM extensions.

  • It contains examples in the standard backtick-delimited spec.txt format, each of which contain a Markdown example and the corresponding canonical HTML.
  • The update-specification.rb script inserts it as new sections before the appendix of generated spec.txt.
  • It should consist of H1 header sections, with all examples nested exactly 2 levels deep within H2 header sections.

glfm_specification/input/gitlab_flavored_markdown/glfm_canonical_examples.txt sample entries:

NOTE: All lines in this example are prefixed with a | character. This prefix helps avoid false errors when this file is checked by markdownlint, and possible errors in other Markdown editors. The actual file should not have these prefixed | characters.

|# First GitLab-Specific Section with Examples
|
|## Strong but with two asterisks
|
|```````````````````````````````` example
|**bold**
|.
|<p><strong>bold</strong></p>
|````````````````````````````````
|
|# Second GitLab-Specific Section with Examples
|
|## Strong but with HTML
|
|```````````````````````````````` example
|<strong>
|bold
|</strong>
|.
|<p><strong>
|bold
|</strong></p>
|````````````````````````````````
glfm_example_status.yml

glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml controls the behavior of the scripts and tests.

  • It is manually updated.
  • The skip_update_example_snapshot* fields control the status of automatic generation of snapshot example entries based on Markdown examples.
  • The skip_running_* control allow Markdown conformance tests or Markdown snapshot tests to be skipped for individual examples.
  • This allows control over skipping this processing or testing of various examples when they are unimplemented, partially implemented, broken, cannot be generated, or cannot be tested for some reason.
  • All entries default to false. They can be set to true by specifying a Ruby value which evaluates as truthy. This could be the boolean true value, but ideally should be a string describing why the example's updating or testing is being skipped.
  • When a skip_update_example_snapshot* entry is true, the existing value is preserved. However, since the YAML is re-written, the style of the string value and its Block Chomping Indicator (|) may be modified, because the Ruby psych YAML library automatically determines this.

The following optional entries are supported for each example. They all default to false:

glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml sample entry:

07_99_an_example_with_incomplete_wysiwyg_implementation_1:
  skip_update_example_snapshots: 'An explanation of the reason for skipping.'
  skip_update_example_snapshot_html_static: 'An explanation of the reason for skipping.'
  skip_update_example_snapshot_html_wysiwyg: 'An explanation of the reason for skipping.'
  skip_update_example_snapshot_prosemirror_json: 'An explanation of the reason for skipping.'
  skip_running_conformance_static_tests: 'An explanation of the reason for skipping.'
  skip_running_conformance_wysiwyg_tests: 'An explanation of the reason for skipping.'
  skip_running_snapshot_static_html_tests: 'An explanation of the reason for skipping.'
  skip_running_snapshot_wysiwyg_html_tests: 'An explanation of the reason for skipping.'
  skip_running_snapshot_prosemirror_json_tests: 'An explanation of the reason for skipping.'
glfm_example_normalizations.yml

glfm_specification/input/gitlab_flavored_markdown/glfm_example_normalizations.yml controls the normalization process. It allows one or more regex/replacement pairs to be specified for a Markdown example.

  • It is manually updated.
  • It has a nested structure corresponding to the example and type of entry it refers to.
  • It extensively uses YAML anchors and aliases to avoid duplication of regex/replacement pairs and allow them to be shared across multiple examples.
  • The YAML anchors use a naming convention based on the index number of the example, to ensure unique anchor names and avoid naming conflicts.

glfm_specification/input/gitlab_flavored_markdown/glfm_example_normalizations.yml sample entries:

# NOTE: All YAML anchors which are shared across one or more examples are defined in the `00_shared` section.
00_shared:
  00_uri: &00_uri
    - regex: '(href|data-src)(=")(.*?)(test-file\.(png|zip)")'
      replacement: '\1\2URI_PREFIX\4'
01_01__section_one__example_containing_a_uri__001:
  html:
    static:
      canonical:
        01_01_uri: *00_uri
      snapshot:
        01_01_uri: *00_uri
      wysiwyg:
        01_01_uri: *00_uri
  prosemirror_json:
    01_01_uri: *00_uri
07_01__gitlab_specific_markdown__footnotes__001:
  # YAML anchors which are only shared within a single example should be defined within the example
  shared:
    07_01_href: &07_01_href
      - regex: '(href)(=")(.+?)(")'
        replacement: '\1\2REF\4'
    07_01_id: &07_01_id
      - regex: '(id)(=")(.+?)(")'
        replacement: '\1\2ID\4'
  html:
    static:
      canonical:
        07_01_href: *07_01_href
        07_01_id: *07_01_id
      snapshot:
        07_01_href: *07_01_href
        07_01_id: *07_01_id
    wysiwyg:
      07_01_href: *07_01_href
      07_01_id: *07_01_id
  prosemirror_json:
    07_01_href: *07_01_href
    07_01_id: *07_01_id

Output specification files

The glfm_specification/output directory contains the CommonMark standard format spec.txt file which represents the canonical GLFM specification which is generated by the update-specification.rb script. It also contains the rendered spec.html which is generated based on the spec.txt as input.

These output spec.* files, which represent the official, canonical GLFM specification, are colocated under the same parent folder glfm_specification with the other input specification files. They're located here both for convenience, and because they are all a mix of manually edited and generated files.

In GFM, spec.txt is located in the test dir, and in CommonMark it's located in the project root. No precedent exists for a standard location. In the future, we may decide to move or copy a hosted version of the rendered HTML spec.html version to another location or site.

spec.txt

glfm_specification/output/spec.txt is a Markdown specification file, in the standard format with prose and Markdown + canonical HTML examples. It is generated or updated by the update-specification.rb script.

It also serves as input for other scripts such as update-example-snapshots.rb and run-spec-tests.sh.

spec.html

glfm_specification/output/spec.html is an HTML file, rendered based on spec.txt. It is also generated (or updated) by the update-specification.rb script at the same time as spec.txt.

It corresponds to the HTML-rendered versions of the "GitHub Flavored Markdown" (GFM) specification and the CommonMark specification.

Example snapshot files

The example_snapshots directory contains files which are generated by the update-example-snapshots.rb script based off of the files in the glfm_specification/input directory. They are used as fixtures to drive the various Markdown snapshot tests.

After the entire GLFM implementation is complete for both backend (Ruby) and frontend (JavaScript), all of these YAML files can be automatically generated. However, while the implementations are still in progress, the skip_update_example_snapshots key in glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml can be used to disable automatic generation of some examples. They can instead be manually edited as necessary to help drive the implementations.

spec/fixtures/glfm/example_snapshots/examples_index.yml

spec/fixtures/glfm/example_snapshots/examples_index.yml is the main list of all CommonMark, GFM, and GLFM example names, each with a unique canonical name.

  • It is generated from the hierarchical sections and examples in the GFM spec.txt specification.
  • For CommonMark and GFM examples, these sections originally came from the GFM spec.txt.
  • For GLFM examples, it is generated from glfm_canonical_examples.txt, which is the additional Section 7 in the GLFM spec.txt.
  • It also contains extra metadata about each example, such as:
    1. spec_txt_example_position - The position of the example in the generated GLFM spec.txt file.
      • This value is the index order of each individual Markdown + HTML5 example in the file. It is not the line number in the file.
      • This value can be used to locate the example in the rendered spec.html file, because the standard CommonMark tooling includes the index number for each example in the rendered HTML file. For example: https://spec.commonmark.org/0.30/#example-42
    2. source_specification - Which specification the example originally came from: commonmark, github, or gitlab.
  • The naming convention for example entry names is based on nested header section names and example index in the header.
    • This naming convention should result in fairly stable names and example positions. The CommonMark / GLFM specification rarely changes, and most GLFM examples where multiple examples exist for the same Section 7 subsection are added to the end of the sub-section.

spec/fixtures/glfm/example_snapshots/examples_index.yml sample entries:

02_01_preliminaries_characters_and_lines_1:
  spec_txt_example_position: 1
  source_specification: commonmark
03_01_blocks_and_inlines_precedence_1:
  spec_txt_example_position: 12
  source_specification: commonmark
05_03_container_blocks_task_list_items_1:
  spec_txt_example_position: 279
  source_specification: github
06_04_inlines_emphasis_and_strong_emphasis_1:
  spec_txt_example_position: 360
  source_specification: github
07_01_audio_link_1:
  spec_txt_example_position: 301
  source_specification: gitlab

spec/fixtures/glfm/example_snapshots/markdown.yml

spec/fixtures/glfm/example_snapshots/markdown.yml contains the original Markdown for each entry in spec/fixtures/glfm/example_snapshots/examples_index.yml

  • For CommonMark and GFM Markdown, it is generated (or updated) from the standard GFM spec.txt using the update-example-snapshots.rb script.
  • For GLFM, it is generated (or updated) from the glfm_specification/input/gitlab_flavored_markdown/glfm_canonical_examples.txt input specification file.

spec/fixtures/glfm/example_snapshots/markdown.yml sample entry:

06_04_inlines_emphasis_and_strong_emphasis_1: |
  *foo bar*

spec/fixtures/glfm/example_snapshots/html.yml

spec/fixtures/glfm/example_snapshots/html.yml contains the HTML for each entry in spec/fixtures/glfm/example_snapshots/examples_index.yml

Three types of entries exist, with different HTML for each:

  • Canonical
    • The "Canonical" HTML.
    • For CommonMark and GFM examples, the HTML comes from the examples in spec.txt.
    • For GLFM examples, it is generated/updated from glfm_specification/input/gitlab_flavored_markdown/glfm_canonical_examples.txt.
  • Static
    • This is the static (backend (Ruby)-generated) HTML for each entry in spec/fixtures/glfm/example_snapshots/examples_index.yml.
    • It is generated/updated from backend Markdown API (or the underlying internal classes) via the update-example-snapshots.rb script, but can be manually updated for static examples with incomplete implementations.
  • WYSIWYG
    • The WYSIWYG (frontend, JavaScript-generated) HTML for each entry in spec/fixtures/glfm/example_snapshots/examples_index.yml.
    • It is generated (or updated) from the frontend Content Editor implementation via the update-example-snapshots.rb script. It can be manually updated for WYSIWYG examples with incomplete implementations.

Any exceptions or failures which occur when generating HTML are replaced with an Error - check implementation value.

spec/fixtures/glfm/example_snapshots/html.yml sample entry:

06_04_inlines_emphasis_and_strong_emphasis_1:
  canonical: |
    <p><em>foo bar</em></p>    
  static: |
    <p data-sourcepos="1:1-1:9" dir="auto"><strong>foo bar</strong></p>    
  wysiwyg: |
    <p><strong>foo bar</strong></p>

NOTE: The actual static or WYSIWYG entries may differ from the example html.yml, depending on how the implementations evolve.

spec/fixtures/glfm/example_snapshots/prosemirror_json.yml

spec/fixtures/glfm/example_snapshots/prosemirror_json.yml contains the ProseMirror JSON for each entry in spec/fixtures/glfm/example_snapshots/examples_index.yml

  • It is generated (or updated) from the frontend code via the update-example-snapshots.rb script, but can be manually updated for examples with incomplete implementations.
  • Any exceptions or failures when generating are replaced with a Error - check implementation value.

spec/fixtures/glfm/example_snapshots/prosemirror_json.yml sample entry:

06_04_inlines_emphasis_and_strong_emphasis_1: |-
  {
    "type": "doc",
    "content": [
      {
        "type": "paragraph",
        "content": [
          {
            "type": "text",
            "marks": [
              {
                "type": "bold"
              }
            ],
            "text": "foo bar"
          },
        ]
      },
    ]
  }

Workflows

This section describes how the scripts can be used to manage the GLFM specification and tests.

Update the GLFM specification and run conformance tests

  1. Run update-specification.rb to update the GLFM specification output specification files.
  2. Visually inspect and confirm any resulting changes to the output specification files.
  3. Run run-spec-tests.sh to run the conformance tests against the canonicalized GLFM specification.
  4. Commit any changes to the output specification files.

Update the example snapshots and run snapshot tests

  1. If you are working on an in-progress feature or bug, make any necessary manual updates to the input specification files. This may include:
    1. Updating the canonical Markdown or HTML examples in glfm_specification/input/gitlab_flavored_markdown/glfm_canonical_examples.txt.
    2. Updating glfm_specification/input/gitlab_flavored_markdown/glfm_example_status.yml to reflect the current status of the examples or tests.
  2. Run update-specification.rb to update the spec.txt to reflect any changes which were made to the input specification files.
  3. Visually inspect and confirm any resulting changes to the output specification files.
  4. Run update-example-snapshots.rb to update the example snapshot files.
  5. Visually inspect and confirm any resulting changes to the example snapshot files.
  6. Run run-snapshot-tests.sh as a convenience script to run all relevant frontend (RSpec) and backend (Jest) tests which use the example snapshots.
    1. Any frontend or backend snapshot test may also be run individually.
    2. All frontend and backend tests are also run as part of the continuous integration suite, as they normally are.
  7. Commit any changes to the input specification files, output specification files, or example snapshot files.