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Extract tagged metadata from a SQL chunk

Source: R/parse-helpers.R
extract_all_tags.Rd

extract_all_tags() scans SQL for specially formatted comment tags (e.g., -- @tag: value) and returns them as a named list. This is exported with the intent to be useful for users extending qryflow. It's typically used against a single SQL chunk, such as one parsed from a .sql file.

Additional helpers like extract_tag(), extract_name(), and extract_type() provide convenient access to specific tag values. subset_tags() lets you filter or exclude tags by name.

Usage

extract_all_tags(text, tag_pattern = "^\\s*--\\s*@([^:]+):\\s*(.*)$")

extract_tag(text, tag)

extract_name(text)

extract_type(text)

subset_tags(tags, keep, negate = FALSE)

Arguments

text

A character vector of SQL lines or a file path to a SQL script.

tag_pattern

A regular expression for extracting tags. Defaults to lines in the form -- @tag: value.

tag

A character string naming the tag to extract (used in extract_tag()).

tags

A named list of tags, typically from extract_all_tags(). Used in subset_tags().

keep

A character vector of tag names to keep or exclude in subset_tags().

negate

Logical; if TRUE, subset_tags() returns all tags except those listed in keep.

Value

  • extract_all_tags(): A named list of all tags found in the SQL chunk.

  • extract_tag(), extract_name(), extract_type(): A single tag value (character or NULL).

  • subset_tags(): A filtered named list of tags or NULL if none remain.

Details

The formal type of a qryflow SQL chunk is determined by extract_type() using a prioritized approach:

  1. If the chunk includes an explicit -- @type: tag, its value is used directly as the chunk type.

  2. If the @type: tag is absent, qryflow searches for other tags (e.g., @query:, @exec:) that correspond to registered chunk types through ls_qryflow_types(). The first matching tag found defines the chunk type.

  3. If neither an explicit @type: tag nor any recognized tag is present, the chunk type falls back to the default type returned by qryflow_default_type().

See also

qryflow_parse(), ls_qryflow_types(), qryflow_default_type()

Examples

filepath <- example_sql_path('mtcars.sql')
parsed <- qryflow_parse(filepath)

chunk <- parsed$chunks[[1]]
tags <- extract_all_tags(chunk$sql)

extract_name(chunk$sql)
#> NULL
extract_type(chunk$sql)
#> [1] "query"
subset_tags(tags, keep = c("query"))
#> list()